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Karl Foord


Karl Foord


Karl Foord


Karl Foord


Karl Foord


Karl Foord


Karl Foord


Karl Foord


Karl Foord - Extension Educator, Horticulture

Light Basics

Note: Measurement of light is a complicated subject. This article can be approached from at least two levels: one level would be to gain an intuitive sense of the graphs, whereas a second level would be a more in-depth approach where individual parameters are explored. For those interested in the latter, references are given at the end of the article.

In Minnesota the number of hours of light essentially doubles between the winter and summer solstices, 8 and 16 hours, respectively. (Figure 1).

M. Pidwirny (

Figure 1: Hourly variations in insolation received for a location at 45° North latitude over a 24 hour period.

The low angle of the sun reduces the number of light photons or energy per unit area meaning that the energy received at mid-day on December 21 is less than one third of that received at mid-day on June 21 (Figure 2: Sun declination angle relative to energy received at 41.7 o N latitude).

Apogee Instruments

Figure 2: Season Comparison of Solar Zenith Angles in Logan, Utah 41.7 degrees N Latitude

In fact the total light energy received in December on average is closer to one quarter of that received in June and July (Figure 3: outdoor daily light integral US).

J. Faust

Figure 3: Outdoor Daily Light Integral U.S.

To survive the winter we bring our plants inside and further reduce light reception through the shading effects of the building. Because plants use light to produce needed metabolic compounds such as sugars and starches, this drastic reduction in sunlight means we have the opportunity to starve our plants.

Plant Selection

To have a good experience with houseplants, we need to choose those plants that can tolerate these "lean" conditions. I have two categories of houseplants, plants that stay inside year-round, and plants that winter inside and summer outside. In the first group I have had success with: African violets (Saintpaulia ionantha), Phalaenopsis orchids, cacti, Cyclamen (Cyclamen persicum), Schefflera (Schefflera actinophylla), and Norfolk Island pine (Araucaria heterophylla). In the second group I have had success with Meyer lemon (Citrus × meyeri), tropical hibiscus (Hibiscus rosa- sinensis), banana (Musa 'Dwarf Cavendish'), pygmy date palm (Phoenix roebelenii), and cycad (Cycas revoluta). All of these plants have the ability to tolerate lower light conditions.

Match your home micro climates to the plants' needs

The best way to handle this is to understand the light needs of your plants and the amount of light entering your house through various windows. The amount of light energy is greatest from the south > west > east > north. In the winter the sun rises south of due east and sets south of due west. Windows facing directly east and west receive sun coming at an oblique angle to the window, reducing energy received.

Karl Foord

Photo 1: Houseplants in south and west corner window BEFORE

I have placed my African violets (Saintpaulia ionantha), Phalaenopsis orchids, cacti, and Cyclamen (Cyclamen persicum) in a corner with south and west facing windows. These plants stay here year around and avoid direct summer sun due to plant and building shading effects (photo 1).

Karl Foord

Photo 2: Houseplants in south and west corner window AFTER

To improve the location I washed the windows and re-potted the orchids to improve spacing (photo 2).

Karl Foord

Photo 3: Houseplants in west window BEFORE

The other plants [Meyer lemon (Citrus × meyeri), tropical hibiscus (Hibiscus rosa- sinensis), banana (Musa 'Dwarf Cavendish'), and pygmy date palm (Phoenix roebelenii) have been placed in western facing windows.

Photo 3 shows the decrease in light level from the center of the room to the window, a 36 fold decrease.

Karl Foord

Photo 4: Houseplants in west window AFTER

Photo 4 shows the plants positioned to optimize their light reception.


Recognize the @ 75% decrease in light energy received from summer to winter solstice. Choose plants that tolerate lower light levels and select locations in your house affording plants adequate light. Recognize the dramatic reduction in light energy as you move away from the window.


Korczynski, P., J. Logan, and J. Faust. (2002). Mapping monthly distribution of daily light integrals across the contiguous United States. HortTechnology 12 (1) pp. 12-16.

Lopez, R. and A. Torres. (2010). Measuring daily light integral in a greenhouse. Commercial Greenhouse Production. Purdue Department of Horticulture. Bull HO-238-W (accessed 12/2/2012)

Pidwirny, M., and S. Jones (2010). Daily and annual cycles of temperature in Chapter 7: Introduction to the atmosphere in, Fundamentals eBook.

Sunmaster (2012). PAR Watts, Lumens, Photons, Lux and Watts.

Calendar: November 1, 2011

Dave Hansen, UMN

Last chance! The Arboretum Apple House will remain open until at least November 6. They have the best supply of Honeycrisp in years and have been picking some high quality late season apples this week. Whether you prefer a tart and juicy Haralson, a sweet Fireside or Snowsweet with a balanced flavor, you will find the apples you enjoy the most right now. For updates on the Applehouse inventory, call 952-443-1409. For more information about the Apple program at the U of M, please visit the U of M Apples website.

Dave Hansen, UMN


Potted chrysanthemums in rich, autumn hues are traditional for Thanksgiving. Choose plants with some buds just opening, rather than in full bloom. They'll last three or four weeks when kept in a bright locations. Discard the plants once their flowers fade. It's not worth trying to plant them outdoors. Even though they might survive our winters, most florists mums won't bloom before hard frost, so they aren't useful in Minnesota gardens.

Apply winter mulch over bulbs and the flowering perennials buy mid-month if the soil hasn't frozen yet. (Ideally you'd wait until it freezes.) You can even spread straw, leaves, or partially finished compost on top of snow. Winter mulch's most important function is to insulate plant roots from fluctuating soil temperatures and keep them safely dormant during early spring warm-ups.

Move houseplants to brighter locations within your home, to compensate for reduced-light levels as days grow shorter and cloudier weather increases. South-or west facing windows are not too bright-- even for "low light" plants, this time of year. Pull the shades or draw the drapes at night, thought to protect houseplants from cold air near window panes. Continue to rotate the plants 1/4 turn every couple weeks so they don't bend toward the light.

Calendar: October 1

Julie Weisenhorn

Acer saccharum (Sugar Maple)

Leave a couple inches of stem attached when you pick pumpkins. Since they have almost no frost tolerance, they must be harvested or protected if frost is forecast. Pumpkins ripen best on the vine, but may turn orange in storage if not completely ripe when picked. Wipe them clean with a damp, slightly soapy cloth, then put them in a warm sunny spot for a week or two to cure them. Store in a cool dark place.

Continue to mow the lawn as needed, and rake fallen leaves so grass doesn't mat down and encourage snow mold development. Or, if the leaves aren't too deep, run a power mower over them several times. This chips them into little pieces that filter harmlessly through the grass into the soil, recycling a small amount of nutrients as they break down. Otherwise, use the leaves to protect bulbs and flowering perennials, or compost them.

As the gardening season winds down, so does the Yard and Garden News. Beginning this month, we will go back to a once-monthly publication schedule until April. See you November 1!

Yard and Garden News Editor: Karl Foord
Technical Editor: Bridget Barton

Calendar: September 15, 2011

Bridget Barton

Three-Mile Drive at the Minnesota Landscape Arboretum, October 2010.

According to the Minneapolis Star Tribune, the Minnesota DNR is predicting the best fall color in ten years, thanks to abundant rain during the growing season, as well as a hot, humid summer. The DNR fall color reports are now available, to help find the most vibrant color in the state. The University of Minnesota Climatology Working Group, a division of the DNR, has more interesting information about the cause of the spectacular color show we enjoy each fall. The Star Tribune also has a great interactive fall color map.

The Minnesota Landscape Arboretum and the Minnesota Grape Growers Association are teaming up for the upcoming collaborative, 4X4 Culinary Series at the Arboretum. For the series, U of M Enologist Katie Cook will lead participants through four food and wine pairings over a series of four dinners prepared by leading Twin Cities chefs. Participants can sign up for any or all of the dinners to experience a full array of local wines and meals this fall and winter. More information can be found on the MN Landscape Arboretum website; Kare 11 also did a feature highlighting the series and local wines.

Order spring flowering bulbs to plant later this month or next. Water them thoroughly after planting. Unless there's ample rainfall, continue watering every couple weeks so they develop good roots before winter. Mulch them once the soil freezes. The longer you wait to plant your bulbs, the less likely they'll come through winter successfully. Tulips are more forgiving than other bulbs, but it's still best not to plant them too late.

Can't get enough University of Minnesota Extension News? Follow UMNExt on Twitter!

Yard and Garden News Editor: Karl Foord
Technical Editor: Bridget Barton

What's happening in the orchard? Blueberries!

Tomato tip:
Consider pinching the growing tip of your indeterminate tomatoes in the next few weeks. By eliminating the growing tip the energy produced by the plant is focused on ripening the tomatoes presently on the vine. If not the vine will continue to produce flowers and fruit that will not ripen before the first frost. The rule of thumb is about 1 month prior to historic first frost. If you have ways to protect your tomatoes from the historic first frost you can likely extend the season for another month, and can prune accordingly.

Calendar: July 1, 2011

Julie Weisenhorn

Beautifully blooming petunias in the Display and Trial Garden on the St. Paul campus of the U of M.

Early maturing vegetables such as leaf lettuce, radishes and spinach turn bitter and go to seed in July's heat. Pull them up, add a little fertilizer, and replant with broccoli, cabbage or cauliflower to harvest next fall. Or, instead of vegetables, you could sow a "green manure" cover crop -- clover, buckwheat, or annual rye-- to keep weeds out. Then turn them into the soil in the fall, before they go to seed, to add nutrients and organic matter for next year.

Make a habit of deadheading (removing faded blossoms) whenever possible from flowering annuals and perennials to prevent infection by the gray mold pathogen, Botrutis. (this disease is favored in warm, humid weather typical of July and August.) Flower infections can ultimately lead to the death of the entire plant. Of course, deadheading keeps plants looking better, too, and encourages them to keep blooming.

Summer lawn tips:

  • Raise the height of your lawn mower blade to 3" and mow when the grass is 4 - 4 1/2" tall.
  • Water the lawn thoroughly when walking across leaves footprints that don't spring right back.
  • Wait to fertilize until late August or September when temps cool and grass grows actively again.
  • Dig up weeds now, but don't spray the lawn with herbicide until fall.

Yard and Garden News Editor: Karl Foord
Technical Editor: Bridget Barton

Calendar: June 15, 2011

Conserve moisture by watering early in the day, when temperatures are lowest and winds have not picked up yet. Try to water at the base of the garden and landscape plants. Use soaker hoses and sprinklers that don't shoot way up in the air; too much water will be lost to evaporation. Avoid watering at night if possible, as foliage that remains wet overnight is more prone to a number of plant diseases. Do water at night, though, if that's your only option.

Yard and Garden News Editor: Karl Foord
Technical Editor: Bridget Barton

Calendar: June 1, 2011


Damage on Chocolate Mint Mentha x piperita f. citrata 'Chocolate'Karl Foord.

  • Fourlined plant bug nymphs love mint, as shown on the photo to the right. Their feeding causes small, necrotic spots. The damage can look a little different on different plants, but is similar enough to recognize. Thanks to Jeff Hahn for identification of the nymph.

  • Check flowering perennials closely for signs of fourlined plant bug feeding-- small brown circular depressions on the leaves. This usually doesn't injure the plants seriously, but it does make them less attractive and sometimes the bugs can truly overrun the plant. It's best to tolerate fourlined plant bugs whenever possible, but if you decide to control them, you must spray soon after you first notice feeding damage. Check out the UMN Extension Garden page for more information.
  • Assess the performance of your spring-flowering bulbs. Lift and discard any that failed to bloom well; they won't improve. Fertilize the others, and allow their foliage to mature naturally. Braiding or tying up the leaves deprives them of the light needed to store energy for next year's blooms. Planting annuals around them, though possible, may keep bulbs

Nymph on Chocolate Mint Mentha x piperita f. citrata 'Chocolate'. Karl Foord.

    too moist during their summer dormancy, resulting in poor growth the following spring.

  • If you need to prune spring-flowering shrubs such as lilac, forsythia, azalea, rhododendron or rose tree of China, in order to shape them and control their size, do it right after they're through blooming. Pruning mid-season or late summer inadvertently eliminates much of the following year's blooms because those buds actually begin to develop shortly after this year's flowers fade!

Yard and Garden News Editor: Karl Foord
Technical Editor: Bridget Barton

Calendar: May 1, 2011


Echinacea purpurea 'Magnus'Julie Weisenhorn.

Most flowering annuals are available as sturdy seedlings at garden center and nurseries, but many will grow just as well or even better when you seed them directly into the garden. Zinnias, cosmos, bachelor's buttons, California poppies and marigolds are good examples of annuals that grow rapidly from seed. But if you want annuals for containers, buy well developed transplants that will look good the minute you pot them up.

Early May is a good time to plant grass seed, but for good results you need to rough up the soil first. Unfortunately, this exposes crabgrass and other weed seeds that will sprout right along with your new grass. To stop most weed seeds, apply a specially formulated version of pre-emergence herbicide right after seeding. The label must state clearly that it's meant for newly seeded lawns, otherwise it will kill desired grass seeds, too.

Attract butterflies to your yard by planting many good nectar-producing flowers. Include coneflowers, Russian sage, Joe-Pye weed, butterfly weed (Asclepsias), beebalm, catmint, Mexican sunflower, and single or semi-double zinnias. Though butterfly larvae (caterpillars) may feed on your plants, don't use any insecticides in the garden. And don't put up "butterfly houses" unless you enjoy them as garden art... butterflies will never inhabit them!

The Yard and Garden News will be going back to a twice-monthly format for the summer! See you on the 15th!

Yard and Garden News Editor: Karl Foord
Technical Editor: Bridget Barton

Calendar: March 1, 2011

Take time to focus on your houseplants before outdoor activities consume most of your gardening energy. Wash accumulated dust from the surfaces and undersides of leaves. Resume fertilizing if you haven't yet done so. Return low-light plants to their spring and summer locations, out of intense sunlight. Transfer plants that have outgrown their old containers to new ones that are only an inch or two larger in diameter. For plant health, be sure pots have drain holes or built-in water reservoirs.

The best time to have shade trees and fruit trees pruned is late in their dormant period, before buds start to open. If you have oaks that need pruning, be sure the job is completed by the end of the month. Pruning or wounding them during April, May of June leaves them vulnerable to developing oak wilt, a fungal disease that can kill red oaks and pin oaks within weeks and is usually fatal to white oaks and bur oaks within a few years.

4-12-10 008.jpgHave you checked out the new UMN Extension website? Don't miss the latest news, University of Minnesota Extension's most recent statewide news releases, Ag News Wire columns, features and multimedia offerings. Find answers to your questions on the Garden page, and Ask a Master Gardener online. Bookmark these pages so they are handy for the growing season!

Yard and Garden News Editor: Karl Foord
Technical Editor: Bridget Barton

Calendar: February 1, 2011


Chrysanthemum 'My Favorite.' Julie Weisenhorn.

  • Why not give a blooming plant, rather than cut flowers for Valentine's Day this year? Choices can range from inexpensive African violets, chrysanthemums, or miniature roses to large azaleas and exotic orchids. Their flowers will last much longer than bouquets of floral arrangements, and with continued care, many can be grown as houseplants and made to re-bloom. Wrap the plant well, then place it in a good-sized plastic bag to trap warm air before putting it in a pre-warmed car to bring to your valentine.

  • Assemble equipment you'll need to start seeds indoors: pots, trays, fluorescent lights that can be raised or lowered, a timer, and, for best results, a heating device to put under containers of germinating seeds. help avoid diseases by using fresh potting soil that drains readily, along with tools and containers that are clean or disinfected. Cool, soggy growing conditions and poor air circulation also favor disease development.

  • Improve your winter landscape by adding plants to your garden and landscape next spring. Spruce, pines, and fir trees are obvious choices, but consider ornamental grasses and other tall perennials that can stand up to the snow. Shrubs such as redtwig and and flowering dogwoods add color, as do many flowering crabapples that hold their fruit all winter.

Be sure to visit the U of M Extension - Garden website for more ideas to beat the winter blues!

Calendar: January 1, 2011

Happy new year from the Yard and Garden News team!

Start the new gardening year by familiarizing yourself with the University of Minnesota Extension's source of reliable, localized information on the web. Visit Garden Info to learn about growing plants indoors, in flower or vegetable gardens, and in landscapes.

Keep holiday poinsettias in tip-top condition for months by placing them near a sunny window and rotating the pots a quarter-turn every few weeks. water the soil thoroughly whenever its surface feels slightly dry; don't wait until the leaves begin to wilt. Fertilize monthly at first, then every two or three weeks as the days grow longer in March. Always mix your fertilizer half strength to avoid problems.

Bring pots of amaryllis up from the basement to force them into bloom. Water them thoroughly, then put them in a sunny window. They usually bloom in six to eight weeks, depending on how warm you keep your home. Often, flower stems appear first, but don't be alarmed if you only see leaves. If the plant received sufficient light last year, flower stems should follow. Continue to water your amaryllis whenever the soil surface feels dry, but wait until late February or March to resume fertilizing.

Calendar and Contributors: December 1, 2010

Make cleaning your houseplant foliage part of sprucing up your home for the holidays. Clean leaves look best-- and they capture more light for photosynthesis. Wash both the surface and underside of each leaf with lukewarm water that's had a drop or two of dishwashing liquid added. For more information, see the wide range of houseplant care publications on the University of Minnesota Extension Garden Info site.

Poinsettia's are among the easiest holiday plants to grow. But first you must choose a plant and get it home without suffering cold damage. It must be wrapped well, then transported in a heated vehicle. Cut the bottom of the pot so excess water will drain out, and place the poinsettia in a bright- even sunny- location. water thoroughly when the soil surface begins to dry, and fertilize monthly after four to six weeks.

Want to see more poinsettias? Spend some time at the Marjorie McNeely Conservatory in St. Paul's Como Park. The annual holiday display will help you forget December's snow and cold!

The Minnesota Landscape Arboretum also has many winter offerings. This month, the Arboretum will be hosting Hot Chocolate Walks, guided walks with a naturalist through the quiet of winter, with a cup of hot chocolate to warm up at the end. Visit the Arboretum website for this and other opportunities to take advantage of the snowy Minnesota landscape.


This month the Yard and Garden News will feature Julie Weisenhorn, Director of the Master Gardener Program and Assistant Extension Professor. We have asked Julie two questions: "What do you like most about your job?" and "What are you passionate about outside of work?"

I have always loved teaching landscaping and plant selection to my Master Gardeners - my three areas of focus! They are the greatest students - full of energy and the desire to learn. They also ask really good questions - they keep me on my toes - and draw excellent conclusions. I love to hear from them how they used the information they learned in my class to help citizens with their gardening questions.

Photography of plants, landscapes and architecture: I love waiting for the right light, the right subject, the right combination of elements and then getting that perfect shot. I love coming upon a unique plant or combination of plants and getting the shot. It's very satisfying to go back over the day's work and say "wow!"

Dogs and landscaping: I love dogs and will always have a dog in my life, my home - and my garden! That means landscaping with the notion that a dog will be a participant and use the landscape as their territory. Keeping expectations realistic when creating spaces, selecting plants and designing for specific needs of the dog are key to having a landscape that is functional, maintainable and looks great.

Music and friends who play music: My personal time is often spent playing music with friends. My husband is a musician and I come from a musical family. I have always loved to sing and am playing better guitar thanks to hanging out and jamming at a local music store on Saturdays. While I don't count on music as a career, I love to perform in groups and play at weddings, benefits, and parties for the pure bliss of the rush you feel when an ordinary song turns out great.

Julie Weisenhorn wormclass09.jpg

Julie Weisenhorn teaching vermicomposting at a Somali school in Inver Grove Heights.

Calendar and Contributors: November 1, 2010

Garden Calendar

Check out more fall tips to reduce snow mold next spring from UMN Extension Educator Bob Mugaas, as featured with Bobby and Belinda on Kare11.

Be a responsible gardener and remove any buckthorn shrubs still growing on your property. They're easy to spot late in autumn when most other shrubs have lost their leaves. Buckthorn has green leaves and small clusters of black berries, with sharp barbs sparsley placed. Unfortunately, they're difficult to dig out. Larger plants will require brush killer next spring or summer. Do you have buckthorn in your yard? Learn more about buckthorn from the Minnesota DNR.

Buckthorn (R. Frangula) and all cultivars are considered to be restricted noxious weeds, according to the DNR. Check this list of Minnesota and Federal Prohibited and Noxious Plants by Scientific Name if you are ever uncertain about something in your yard.


The Yard and Garden News will now feature brief profiles of the contributors! We've asked UMN Extension Educator, Kathy Zuzek "What do you like most about your job?" and "What are you passionate about outside of work?"

Kathy Zuzek, UMN Extension Educator, Horticulture

The best parts of my job are being able to teach horticulture to invested students and working with other extension educators who enjoy helping others to learn as much as I do. During my 20 years as a research scientist I often commented on how much I enjoyed presenting to Master Gardeners, so becoming an Extension Educator and part of the Master Gardener education team was and continues to be a thrill.

I am passionate about plant hybridizing and developing attractive & adapted landscape cultivars for northern climates, parenthood, Minnesota's Arrowhead region, camping, hiking, kayaking, and my dogs (That's Max in the photo. Kirby, my golden retriever, missed that camping trip.)


Yard and Garden News Editor: Karl Foord
Technical Editor: Bridget Barton

Calendar and Contributors: October 15, 2010

Getting ready to say goodbye to your garden for the winter? U of M Horticulture Science Professor Bud Markhart offers ways to "Spend time in garden now to save money later" in this KARE11 article. (Don't miss the video on the right side!) And remember- when it comes to your garden, it's not goodbye, it's see you later.

*New this month!*
The Yard and Garden News will now feature brief profiles of the contributors! We've asked "What do you like most about your job?" and "What are you passionate about outside of work?" This month will start with the Yard and Garden News Editor, Karl Foord, and the Technical Editor, Bridget Barton.

Karl Foord, UMN Extension Educator; Yard and Garden News Editor
The thing I like most about my job is learning and discovery. For me these are horticultural and biological topics. Such as learning about the importance of pollinators, how insects fly, the variation in the taste of fruits especially apples and strawberries, and how plants respond to their environment. I like capturing information and putting it in a form that is easy for people to absorb, especially visually.

I am passionate about photographing birds and insects in flight. I am passionate about geology the history of the earth and its organisms, and my dogs (Indiana Jones on my right and Moose on my left).


Bridget Barton, UMN Extension Master Gardener State Program Assistant; Yard and Garden News Technical Editor

The best part of my job is the variety! From working with the Master Gardeners to being the technical editor for the Yard and Garden News- every day is something new! I also love the opportunities I have to meet and work with such interesting and talented people. It's been awesome getting to know Master Gardeners from all over the state, and to see the amazing projects they are working on in their communities. I'm lucky to be part of such a unique program!

I am currently working on my Master of Public Policy at the U of M Humphrey Institute. When I'm not at work or at school, I try to spend as much time outdoors as possible. I also love gardening, dogs, trips to Duluth and the Minnesota Twins (even after the disappointing playoffs last week!)

10-12-10 072.jpg

Garden Calendar: October 1, 2010

Starting this month, the Yard and Garden News will move to publishing just once per month for the winter. We'll return to twice monthly in the Spring!

Watch November 1 for an article on the challenges facing honey bees by UMN Bee Researcher, Marla Spivak. Spivak, a nationally and internationally respected entomologist, recently won a MacArthur Foundation Genius Grant for her work on the health of honeybees!

Garden Calendar:

  • The first frost in the Twin Cities Metro area is expected Sunday! Be sure to cover any tender annuals, and keep an eye out for frost damage! Wondering what the historic frost dates are for your area? Look up your city in this handy table from the Minnesota Climatology Working Group!

  • Be sure to protect hybrid teas and other roses that aren't winter hardy here, around mid-month. It's a gamble when canes are damaged when temperatures drop below 20 degrees F. Mounding soil over over the crowns or tying canes is more work, but much more effective than just using Styrofoam rose cones. Just rake leaves over the bases of hardier roses.

  • Tackle garden clean-up chores before cold, wet weather makes them more difficult. Pull frost-damaged annuals and vegetables, cut back damaged perennials, empty large containers and bring them into the basement or garage where they won't freeze and crack.

Garden Calendar: August 15, 2010

  • The apple harvest is starting, with Paula Reds and State Fairs already ripe. The Zestar in Southern Minnesota should be ready for harvesting within the next week or two.
  • Sooty blotch and fly speck fungi have shown up. (See pictures)
  • Disease and insect pressure has been high this summer.





Photo credits: Karl Foord

Yard and Garden News Editor: Karl Foord

Technical Editor: Bridget Barton

May 2010 Garden Calendar

Contributors: Karen Jeannette, Yard and Garden News Editor
Including Excerpts from the 2010 Minnesota Gardening Calendar

This month Bob Mugaas tells us the crabgrass has emerged early (Home Lawn Care - Recapping the very early spring of 2010 and what's next for timely information about Lawns) and Jeff Hahn says Spring Insects are Early this year, too. Gardeners across the state have been inquiring if they can plant and perform other garden and yard tasks earlier than in past years. Below we provide advice for this gardening season come early.

Advice for the Gardening Season Come Early

When to Plant Flowers

Despite the warmer and earlier growing season, the answer to, "Is it safe to plant perennials and annuals?" is still "Wait until mid-to late May to plant perennials and until after your area is frost free before planting flowering most annuals."

Why Wait?  In most Minnesota locations, perennials can be planted after mid-month, but wait until you're certain there will be no more frost before adding flowering annuals to the garden. Most, including impatiens and geraniums, have no frost tolerance. Pansies, violas, and johnny jump-ups are among the few annuals that will not be killed or badly damaged by frost. Calendulas, snapdragons, and sweet alyssum may also be planted a little early. 

You can identify when your area is likely to be frost-free using the MN spring frost-free map:  

When to Plant Vegetables


Photo 1: Kale and other cool season vegetables can be planted as soon the garden bed is ready. Karen Jeannette.

Which vegetables can I plant and when? You can sow early "cool-season" crops such as lettuce, cabbage, cauliflower, broccoli, Brussels sprouts, and onions immediately after preparing your garden plot.

Warm season vegetables, like tomatoes and peppers should be planted after the last chance of frost.  See "Planting the Vegetable Garden": for guidance on when to plant and how far apart to space your vegetables.

Keep Up with Early Pests and Diseases

Plant Diagnostic Modules: Pictures, simple descriptions, and easy to follow management instructions make it easy to stay ahead or just keep up with plant pests and problems using any of the University of Minnesota Garden Info Diagnostics Modules:

Stay ahead of disease this year with diseases management tips in this month's article by Michelle Grabowski: Keeping Plants Healthy and Green While Going Green

When to Perform Lawn Care

The lawn care calendar guide "Upper Midwest Home Lawn Care for Cool Season Grasses" ( is a helpful guide for scheduling lawn maintenance. However, this month, learn how to adjust your lawn maintenance practices for this earlier than normal growing season with Bob Mugaas' timely article, Lawn Care: Recapping the very early spring of 2010 and what's next for timely information.

For more information on lawn care, see the University of Minnesota Garden Info lawns section:


Are you starting a raised bed? Ordering soil? Adding Compost? Find information on soil topics at the University of Minnesota Garden Info soils section:

You needn't test your garden soil annually, but if plants have grown poorly the past year or two, despite being in a sunny location and receiving normal care, visit U of M Soil Testing Lab web site: .  You'll get a questionnaire with instructions on taking and sending in samples, If the problem is due to a nutrient imbalance, excess alkalinity, or acidity, they'll suggest a remedy, with respect to what you are growing.

Small Fruits

If you'd like to grow some fruit in your yard, but don't have room for apple or pear trees, consider planting Minnesota-hardy blueberries, raspberries, or strawberries. You need an area well-drained soil and plenty of sunlight -- a minimum of six to ten hours daily. More is better. In addition, blueberries need acidic soil to thrive. Have your soil tested for specific information on acidifying your soil before planting them. For more information regarding fruit varieties and culture, see the Fruits section of the U of MN Gardening Information website:


See the Extension listings of garden tours, horticulture diagnostic clinics, workshops, and plant sales @

April 2010 Garden Calendar

Contributors: Karen Jeannette, Research Fellow and Yard and Garden News Editor; excerpts from the 2010 Minnesota Gardening Calendar.

Plant tips

soil sample.jpg

Photo 1: Soil sample from a shade garden area. Karen Jeannette.

Prepare Your Soil


Need ideas for the vegetable or edible garden?


  • Fertilize your lawn to keep it growing vigorously enough to help keep weeds out. Wait until you've had to mow it once or twice though, so you know the roots are growing actively and can make good use of the added nutrients. Seep up and reuse any granules that land on hard surfaces such as sidewalk or driveways, then water the fertilizer lightly into the soils so it "catches" and won't easily wash into storm drains when it rains.
  • If you've seen crabgrass appear early in warmer parts of your landscapes (by sidewalks, driveways, or south-facing slopes) in the past, apply a pre-emergence herbicide towards the end of April in the Twin Cities areas, a week or more later farther north. Otherwise, wait until early to mid-May to spread crabgrass preventer. Whether using a traditional product or corn gluten meal, you must water the lawn lightly afterwards to activate the herbicides ability to stop weed seeds as they sprout.

Trees, Shrubs, Flowers


Photo 2: Mulch used for winter protection can be removed gradually as soil and mulch thaw. Karen Jeannette.

  • Begin to remove protective cover from bulb beds, non-hardy roses and perennials in stages as soil and mulch thaw. Don't rush to uncover tender plants, though. Mulch helps prevent them from coming out of dormancy too early, when damaging cold is still a possibility. Rose canes will be okay as long as temperatures hover around twenty degrees, but most flowering perennials will die back when it's that cold.

  • Prune shrubs grown for their foliage rather than flowers, as soon as their buds swell. (Early pruning removes flower buds.) Many shrubs - dogwood, alpine currant, burning bush, and others produce tiny flowers, but they're not showy enough to worry about eliminating them. Wait to prune junipers, yews, and other evergreens until you see this year's new growth expanding. Prune forsythias, azaleas, lilacs, and other flowering shrubs only after they're finished blooming. For more about pruning flowering shrubs to maximize bloom see:
  • Don't prune or take care to avoid wounding oaks from April through October. April begins the period of high risk Oak Wilt susceptibility. If trees are accidentally wounded or pruning is unavoidable, cover the wounds immediately-within minutes-with one of the preferred materials such as water-based paint or shellac. For more information on Oak Wilt, see:
  • Dormant, bare-root trees and shrubs are often sold for planting in Minnesota during the month of April. See this month's article on Planting Bare-Root Woody Plants
  • When is it safe to plant perennials and annuals? Wait until mid-to late May to plant perennials and until after your area is frost free before planting flowering most annuals.  See the MN spring frost-free map to identify when your area is likely to be frost-free:   


March 2010 Garden Calendar

Contributors: Karen Jeannette, Research Fellow and Yard and Garden News Editor; excerpts from the 2010 Minnesota Gardening Calendar.

Plant Tips


Photo 1: March is a good time for pruning out disease. Shown here: Black Knot on Prunus. Karen Jeannette.

  • Inspect your apple or crabapple trees for fire blight so you can prune out all traces of the disease this month. You might also find the blackened, dead branch tips on pear trees or mountain ash. Check also for black knot swellings on chokecherries and other members of the cherry family. Prune at least six inches back in to healthy wood when you remove diseased tissue. If possible, dip your pruners into bleach solution between cuts.

See the following articles from the March 1, 2007 Yard and Garden News to best implement sound pruning practices:Pruning Tools, Pruning Cuts, Pruning Out Galls and Cankers

  • Start seeds that need eight to ten weeks growth indoors under fluorescent lights by mid-month. Sweet alyssum, blue salvia, and dianthus pinks are just a few such seeds. Peppers, eggplants, and leeks are among others. Tomatoes may be started at the same time, but plants will be rather large when you put them outdoors. It's better to wait until the end of the month to plant tomato seeds indoors.

  • Check produce you've kept in cool storage to make sure nothing is turning soft or rotting. Remove anything suspect, as problems can readily spread. Winter squash, onions, apples, and potatoes all have finite storage life, particularly if temperatures are warmer than ideal. Non hardy summer bulbs, roots, and corms such as dahlias, tuberous begonias, canna or calla lillies may also soften or shrivel if temps are too high or conditions too dry.
  • Heavy spring snowfall often weighs down evergreen boughs and flattens newly emerging bulbs. It's probably best to just let the snow melt off on its own. If you prefer to remove it from evergreens, scoop it off gently rather than hitting the branches. They're still brittle this time of year and prone to breakage. Snow won't permanently harm bulbs, though they might not straighten up completely this year.

  •  Fertilize houseplants now that days are growing noticeably longer


February 2010 Garden Calendar

Contributors: Karen Jeannette, Research Fellow and Yard and Garden News Editor;  Michelle Grabowski, Extension Educator;  excerpts from the 2010 Minnesota Gardening Calendar, and Arboretum News Feb/Mar issue.

Plant tips

Seed & Plant Selection


Photo:Seed catalog cover from 1913. A mini-exhibit of seed catalog covers can be seen in walkway from the restaurant to the Snyder building at the Minnesota Landscape Arboretum. Anderson Horticultural Library. Pre-copyright.

  • Read seed catalogs and favorite gardening magazines for new ideas.  Good planning now allows you to avoid some impulse purchases later.  Look for flower and vegetable cultivars with superior disease-resistance, but check that they'll mature in our relatively short growing season.  Seek out perennials rated hardy enough for Minnesota: USDA 3 in the north, zone 4 in the southern two-thirds of the state, and possibly zone 5 for well-sheltered parts of the Twin Cities. (Zone 5 plants are always more risky). -- This is a 2010 Minnesota Gardening Calendar Tip.

  • Visit the The Anderson Library, located at the Minnesota Landscape Arboretum, to view the new 2010 seed catalogs arriving daily.   The catalogs now number more than 1, 000!  For those that can't make it to the library in person, the Anderson Library also hosts seed catalog information available at Plant Information Online (  Want to learn more? There are several ways you can learn more about using Plant Information Online? See the video @ ttp:// or attend a class. Plant Information Online Classes will be held: Feb. 9 & 23, Mar 9 & 23; 10:30 - 11 a.m. or arrange a time to stop in.  Call the Library for help at 952-443-1405.

Pruning Advice

  • Have shade trees and fruit trees professionally pruned this month or next.  It's easier to see a tree's structure when no leaves are present, and the fresh cuts won't pose a disease or insect problem to oaks, elms, apples, or other trees when pruned in winter.  Some trees, such as maples, birch, honeylocust are likely to drip lots of sap from wound sites in spring, but they should be fine as long as no more than 25% of their canopy was pruned out.  This is definitely not a do-it-yourself project, though.   For more information on hiring professionals to prune shade trees, see: Knowing When to Hire an Arborist -- This is a 2010 Minnesota Gardening Calendar Tip.

Valentines Flowers

    • Keep Valentines Days flowers attractive as long as possible by setting them in a cool location when you're not around to enjoy them.  Put them in a spotlessly clean vase filled with barely warm water and floral preservative.  Add more water and preservative solution as the level drops, replacing it as soon as it appears cloudy.  Trim off any foliage that would sit below water, as it rots easily, and make a fresh cut at the base of each stem whenever you change the water. -- This is a 2010 Minnesota Gardening Calendar Tip.


  • The Minnesota Landscape Arboretum will present "The Great Hall of Orchids--Passport to Paradise," Feb. 12 through March 14. A preview event is scheduled for Feb. 11. The exhibit will feature a variety of orchids--including many unique species and hybrids--all grown by renowned orchid expert Jerry Fischer and his Orchids Limited greenhouse of Plymouth. The orchids will be displayed in the Great Hall of the Oswald Visitor Center. Free with arboretum gate admission.

January 2010 Garden Calendar

Contributors: Karen Jeannette, Research Fellow and Yard and Garden News Editor, Michelle Grabowski, Extension Educator, and excerpts from the 2010 Minnesota Gardening Calendar.

January Tips


  • Pay special attention to your houseplants to keep them looking healthy this winter. Sun is weaker and days are shorter, so move plants to brighter windows if possible. Combat low indoor humidity by grouping plants together, checking their soil frequently and watering thoroughly with room temperature water whenever the soil feels dry a little below the surface. Wipe stems and leaf surfaces (upper and lower) with a soft wet rag to remove dust and allow maximum light penetration.  Find more information in the Gardening Information houseplants section. -- This is a 2010 Minnesota Gardening Calendar Tip.
  • The low humidity of most MN houses means that many fungal and bacterial leaf spots and blights do not thrive on houseplants during the winter months. Root rots however can be a problem for overwatered plants. To avoid root diseases, use pots that have drainage holes at the bottom. Choose a potting media that provides appropriate drainage. Before watering, test the potting soil with your finger to determine if the plant needs water. Heavy water logged soils that are never allowed to dry out will encourage root rotting fungi and can result in the wilting and death of infected plants. Find more information about houseplant diseases in the Gardening Information houseplant diseases section. --Michelle Grabowki, Extension Educator


  • Spread sand on icy sidewalks, rather than commercially prepared ice-melting chemicals, all of which are potentially damaging to nearby plants.  Even fertilizer (sometimes suggested for its ice melting properties) can burn plant roots where it accumulates.  To get sand to adhere to the ice, dampen it with a little hot water then throw it sideways, so it skitters across the ice.  In spring, sweep it off hard surfaces for re-use. It poses no harm to surrounding soil. Find more about plants and ice-melting chemicals by viewing the brief: Effects of De-Icers on Trees and Shrubs  -- This is a 2010 Minnesota Gardening Calendar Tip.


The Northern Green Expo, January 6-8, 2010
The Minnesota Green Expo is now The Northern Green Expo and one of the largest Horticulture Expos in the nation. It is geared towards all sectors of the Horticulture/Green industry (arborists, florists, nurseries, greenhouses, landscapers, turf specialists, groundskeepers, etc.) More information can be found at:

December 2009 Garden Calendar

Karen Jeannette, Yard and Garden News Editor
Including excerpts from the 2009 Minnesota Gardening Calendar


Photo 1: Korean pine tree in the MN Landscape Arboretum pine collection. MN Landscape Arboretum.

It's not too late to protect your plants from Minnesota winter sunscald, animals, salt, snow, ice, and winter discoloration.  See: Protecting Trees and Shrubs Against Winter Damage

Mulch when the ground is frozen to keep the ground frozen, by applying a 4 - 6 inch layer of mulch (i.e. clean straw or leaves) over perennials or at the base of trees and shrubs.  Mulching to keep the ground frozen will help prevent those soil freeze-thaw cycles that can cause damage to roots and heaving of new plantings and perennials above the soil line.

Need to review which trees to select for Christmas?  See Kathy Zuzek's December 2008 article: It's Time for the Christmas Tree
Is your yard or garden ho-hum this time of year? Get inspired with Plants for Winter Interest  or visit your favorite full-size evergreens at the Minnesota Landscape Arboretum's arborvitae, pine, spruce, and dwarf conifer collections.

2010 Minnesota Gardening Calendar

The 2010 award winning 12-month Minnesota Gardening Calendar is available for sale. Full color photographs highlight each month. Also find timely tips for lawn, garden, and houseplant care, with a special feature: Using Vines in Minnesota Home Landscapes. Maps of average frost-free dates and USDA Plant Hardiness Zones for Minnesota are included. Extension's 18 Regional Centers are listed and information about horticultural programs, services, facilities, and organizations in Minnesota are featured.

See a web preview and ordering information @

Below we share the 2009 December Minnesota Gardening Calendar tips:

  • Check Christmas tree stands daily, so they never run out of water.
  • Thumbnail image for MN2010gardencal.jpg

    Photo 2: 2010 Minnesota Gardening Calendar.

    Paperwhite narcissus are wonderful winter flowers. Buy some bulbs for yourself and to give as gifts.  With clusters of small flowers in white, cream, or yellow, they need to special treatment to bloom.  Plant them in pebbles or soil; just keep the base and roots wet.  Paperwhites do best in a cool location with good sun, but will bloom anywhere -- albeit on floppier stems that will need staking or tying to stay upright.
  • Choose a fresh Christmas tree that meets your needs. Balsam fir is more fragrant; Fraser fir is also fragrant and very popular. Norway pine has stiff branches and needles that will hold heavy ornaments, while white pine has fragrant needles that are softer and longer -- more appropriate for lightweight ornaments.  White spruce is excellent as a table-top tree, as is the tropical houseplant, the Norfolk Island Pine.
  • Though poinsettia sap may be irritating, the plant is not toxic when eaten. Unfortunately, some traditional holiday plants can be dangerous if eaten, though especially by a small child.  Set holly and mistletoe out of reach, and dispose of any berries that drop off.  Ornamental peppers aren't poisonous, but they can be so "hot" that tasting them, or even handling them and rubbing your eyes can be painful.
  • Take time to check stored dahlia tubers, canna bulbs, and produce such as potatoes or winter squash.  Look for shriveling, soft spots, mold, or other signs of trouble.  Discard damaged bulbs and tubers. Often rotting is a sign the bulbs were wounded when they were dug up, or that storage temperatures are too high or there's insufficient air circulation.
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