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We aren't always able to answer everyone's text'd questions on the air, so we try to post a few along with answers here in the Yard & Garden News blog. Remember that you can always visit the U of M Extension Garden website for loads of gardening resources.

Hope you join us and our host Denny Long every Saturday, 8-9am, on WCCO Smart Gardens and happy gardening!

From Dave in South St Paul:
My tomatoes are flat and rotting on the bottom. What causes this? I water at the base and they are in containers.

Answer: This is a condition called "blossom end-rot". It is the result of calcium deficiency in the developing tomato fruit. This does not necessarily mean there is not enough calcium in the soil though - just that plant is unable to acquire it. This is due to environmental conditions such as fluctuations in soil moisture, heavy applications of nitrogen fertilizer, and injury roots.
Read more ...

Question: Why do my squash and cucumbers always cross-pollinate? They are planted 15 feet apart.
It's typical for Curcubits varieties to cross-pollinate. They are in the same genus, they bloom at the same time and they are both pollinated by (usually) bees. Successful pollination produces a seed(s) and the tissue that surrounds it. It's important to note that this year's pollination will produce the seeds for next year's plants provided you save seed. Therefore, if you are planting seeds from a seed packet you purchased or transplants you purchased from a greenhouse, you should get the kind of squash / cucumber on the labeled. It's next year you  may get a variation on the original seed due to cross-pollination.

Question: I have had some success wintering begonias. Do you have suggestions for more success?

Answer: When you bring plants indoors for the winter, take this opportunity check them thoroughly for insects and insect eggs especially under the leaves. Wipe / rinse leaves, remove any signs of insects like webbing, and remove/dispose of dead leaves and flowers both on the plant and on the soil surface. Transplant into a clean pot with new potting soil. If the plants are large, consider cutting the plants back about 1/3 to just above a leaf node (a node is the point where a leave grows from a stem). Water and place in a sunny window. Begonias do not do well when over-watered, so check the soil about 2" down with your fingers before watering (recommended for all houseplants). and water if dry. You may find plants that are brought in from the out of doors will drop leaves initially. Remove the dropped leaves and continue watering as usual. Wait to fertilize when new growth appears with a complete fertilizer - 10-10-10 (N-P-K) or similar - at half the recommended strength.

Question: We want to seed about an acre. What type of seed do we use that takes, grows fast, and makes a great grass?

Answer: Choose a grass variety based on your conditions (the amount of light, soil type, moisture level) and based on the kind of activities for which you plan on using the area (sports, low-traffic, play area). Here is a good resource: Turfgrass Selection for Sustainable Lawns

You'll see from the Upper Midwest Home Lawn Care for Cool Season Grasses calendar that mid-August to mid-September is the optimal time for seeding your lawn. Seeding in this time period provides cooler temperatures, encourages germination, and enables the grass seed to form healthy roots before gradually going dormant for winter.

Question: Plum tree loaded with fruit. When is the best time to prune so the branches are not on the ground?

Answer: A good problem to have! Support the plum branches with sawhorses, PVC pipe, or other sturdy braces. Harvest the fruit as soon as it is ripe to reduce attracting pests like yellow jackets or birds damaging fruit. Then prune the tree when it is dormant - March or early April in Minnesota. See Stone Fruits for Minnesota Gardens for specifics on pruning including diagrams. Extension also has a great publication on pest management for stone fruits here.

Question: My Hydrangea doesn't have any flowers on it yet. Do they bloom every year?

Answer: Hydrangeas that are hardy in Minnesota typically bloom every year. Factors that can influence blooming include:

  • whether the plant is hardy in your zone (example: the Hydrangeas from a florist are not typically hardy for our landscapes);
  • weather issues such as late frosts that affect flower buds;
  • the amount of light the plant receives;
  • fertilization;
  • pruning techniques - some people prune off flower buds unknowingly;
  • whether the plant blooms on old or new wood;
  • animal damage such as deer browsing.

Some Hydrangeas are just starting to bloom now too. Without knowing the kind of hydrangea and the care you have given it, it's hard to say why your particular plant isn't blooming. However, we have had numerous people ask why their Endless Summer Hydrangea looks healthy, but doesn't bloom or bloom well. Here are some reasons: Why my Endless Summer Hydrangea didn't bloom

From Paul Cherba: I am getting powdery mildew on my lilacs. Or something white. What can I do about that?

Answer: Common lilacs often get powdery mildew at this time of year due to higher humidity levels. It's typically more cosmetic than detrimental to plant health, and the spores are common and windblown, so there isn't a way to avoid it now or any action to take. Fungicides are available to spray. They are most effective if used at the onset of the mildew (see publication reference below).

Choosing plants that are resistant to pests like powdery mildew is the best option for minimizing its affect. Spacing plants according the their mature size and pruning to increase light and air circulation through the canopy / shrub also is helpful. Prune lilacs within two weeks of flowering before they set flowers buds for next year. Watering at the base of the plant will help keep plant leaves free of water droplets that can hold bacterial and fungal spores. More on powdery mildew on lilacs.

Question: My impatiens were beautiful and now they have been snipped of their leaves and flowers with only stalks left.

Answer: If the leaves have been eaten (they are not lying on the ground), then I would say it was rabbit damage or deer damage. If the leaves have dried up and fallen off the plant, you may have a disease such as impatiens downy mildew. This is a relatively new pest for Minnesota gardeners that affects shade-loving impatiens Impatiens walleriana (not New Guinea impatiens). White fluffy growth forms on the underside of the impatiens leaves. There is no cure and the plants should be removed. Avoid replanting Impatiens walleriana in the same bed. Read more here.

Question: I plan on planting an Autumn Blaze maple where my hackberry once was. When is the best time to plant this?

Answer: Planting a diversity of trees is really important. Trees provide shade, habitat for birds, animals and beneficial insects, and create canopies that cool our landscapes and homes - not mention being beautiful and valuable additions to our landscapes. Late summer / early fall is a good time for planting trees, so right now! Cooler temperatures mean less heat stress on the new trees. Here's a helpful Extension publication on planting trees. Good luck!

P1220417.JPGLandscape design is always a popular subject and smart gardeners think "sustainability" when they plan a landscape project. People are eager to try new things in their gardens. Likewise, our season is so short, we have an inherent need at this time of year to get our hands dirty!

Jim Calkins and I are teaching two sessions (May, June) of our landscape design short workshop this spring through the LearningLife program here at the University of Minnesota College of Continuing Education. These are designed for home gardeners who want some good basic fundamentals on sustainable landscape design that they can apply in their own yards and gardens. These are intensive classes and are by no means meant to replace the huge benefits of securing the services and talents of a professional designer. What we have found is that after taking our workshops, people stop making - like choosing an 10x10 ft shrub for a 5x5 ft area or thinking they need to keep trying to grow turfgrass in a narrow shady side strip along their house.

Hope you can join us at one of our upcoming sessions! They are lots of fun and loaded with information. Visit the link below for more information:  U of Minnesota College of Continuing Education LearningLife Program.

Saturday mornings are a good time to grab a cup of coffee, tune tWCCO.jpghe radio to WCCO 830AM, and listen U of M Extension answer listeners' questions about everything from aphids to zinnias, from grapes to grasshoppers. Heck, we just like talking about Minnesota gardening!

Saturdays, 8-9am on WCCO radio, 830 on the AM dial. year-round
Host: Denny Long
U of M Extension Smart Garden team: Julie Weisenhorn, Sam Bauer, Mary Meyer
Extension Master Gardener volunteers: Theresa Rooney (Hennepin County), Darren Lochner (Hennepin County)
Listen for special guests like Jeff Hahn, John Loegering, Karl Foord ....!
Podcasts of previous shows here: WCCO Smart Gardens

Starting seeds = Spring

Tomato seedlings 041414.jpg

Planting seeds is a sure sign of Spring. Luckily here in Horticultural Science, there is no lack of seed starting happening. My Master Gardener friends, who work on campus, and I started seeds for the 2014 annual seed trials in the greenhouses. The trials are in their 32nd year (I think) and this year, over 100 people are participating by planting and growing out the seeds in their home garden, school gardens, community gardens, and demonstration gardens. On campus, our seed trials can be found in the Department's Display and Trial Garden located at the corner of Gortner and Folwell Avenues on the U of MN St. Paul campus. Trials this year include six herbs for tea, and six varieties of container tomatoes, bull horn peppers, spinach, yellow squash, carrots, shasta daisy, and alyssum. Seed trial results are published each year in the spring issue of Northern Gardener magazine.

I also started some seeds for the Gopher Adventures garden. GA is a day camp for kids here at the U. Kids ages 5-13 can choose to do all sorts of activities at the U from computers to rock climbing to art and dance to - yep - gardening. Master Gardeners and I plant a children's garden on the west end of the display garden. Edible plants, flowers, trees, monarch way station, plants for pollinators - even a miniature garden called "Little Goldy's Garden" complete with a very small golden gopher (it's a magnet on a stick). Last year we had straw bale gardens and pallet gardens. The seeds I started for GA are in my office on a heat mat under a grow light. I used a tray with fifty Earth plugs from Seeds of Change. I used my own seeds from home and planted a couple kinds of peppers, nasturtiums, Salvia, Echnicaea, basil, teddy bear sunflowers, and even a mystery seed that will hopefully emerge (and I can identify). This year, we'll be planting Smart Snacks - an Arboretum educational program about plants that are good snacks for people and pollinators.

Seeds are amazing. Everything needed to grow a plant (water and soil not withstanding) are encapsulated in a seed. Everyone should plant a few seeds and feel a little amazed at the result!

P1230029.JPGIn 2013, our Legislature directed the Minnesota Department of Agriculture to develop BMPS - "best management practices" - for protecting insect pollinators - bees, moths, wasps, butterflies, etc. The MDA has published the Pollinator Report: Pollinator Bank, Habitat Protection and Pesticide Special Review. I am still reading it. Thought you all might like to as well.

As noted in the Executive Summary (pg. 4), the objectives of the report are: "(i) provide interpretations of the term 'pollinator bank' and propose feasibility, constraints, and uncertainties of the various interpretations; (ii) delineate past, present, and future efforts by MDA, DNR, UMN, MPCA, BWSR and MnDOT to create and enhance insect (native and commercial) pollinator nesting and foraging habitat, as well as to establish and protect pollinator reserves or refuge areas by using Best Management Practices (BMPs); (iii) discuss efforts and progress on developing BMPs to establish, enhance, protect, and restore pollinator habitat that will ultimately be incorporated into pesticide applicator and inspector training; (iv) outline the process and criteria of a special review of neonicotinoid insecticides, and provide a status update on the process, criteria, and progress of the special review of neonicotinoid pesticides registered by the Commissioner for use in this state currently and in the future."

Feel free to pass it on!

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