In this issue of the Yard and Garden News:
July 2011 Archives
Bob Mugaas and Kathy Zuzek, UMN Extension Educators
Reports continue to be received regarding herbicide injury to white spruces, white pines and a variety of other woody and herbaceous landscape plants. The herbicide in question is Dupont's Imprelis, whose active ingredient is aminocyclopyrachlor. It belongs to a new class of broadleaf weed control herbicides which are similar, but not identical, to existing products such as triclopyr or fluroxypyr, both commonly used for control of more difficult lawn weeds such as clover and creeping Charlie.
Aminocyclopyrachlor is classified as a synthetic auxin or growth regulator type of herbicide. In susceptible plants, the herbicide produces characteristic twisting and curling of the foliage ultimately leading to plant death. Most of us have probably observed these effects on dandelions that we have treated with home lawn weed control products containing 2,4-D and/or dicamba, two other growth regulator type of herbicides but with different chemistries than aminocyclopyrachlor.
Dupont introduced Imprelis to the professional turfgrass management industry this year. It has a track record from various research efforts of providing good to excellent control of some of the more difficult to control lawn weeds (e.g., creeping Charlie, wild violets, clover and Canada thistle). However, what is also being observed in many of the northeastern and midwestern states is significant, unanticipated damage to certain spruce species and white pines (Photos 1 and 2) with a scattering of injury reported on other conifers and broadleaf plants.
When initial reports started showing up around the end of May into June from the northeastern states, the two conifer species most commonly showing injury were Norway spruce (Picea abies) and white pine (Pinus strobus). When injury reports began coming into our own Department of Agriculture and Extension a short time later, most of the injury was on white spruce (Picea glauca), (Photo 3), including its geographical variety Black Hills spruce and white pine, again with a scattering of injury to other conifer and broadleaf plants. Colorado blue spruce (Picea pungens) has also shown some injury but generally much less dramatic than seen on white spruce or white pine.
As one might imagine, this kind of injury has created enormous concern among homeowners and professional lawn care applicators alike. The two biggest questions on everyone's mind is "Will the trees survive?" and if so, "Will their aesthetic landscape qualities be completely ruined and hence still need to be replaced?" Unfortunately, in all but the most severely damaged trees, it's a bit of a wait-and-see situation. In this area, the white spruce and white pine trees observed so far show damage only on the new or current year's growth, but, that is where new buds are formed for next year's growth (Photos 4 and 5). If this year's growth is lost, no new buds will have been formed and next year's growth may be sporadic around the tree and at worst the tree may still end up dying.
However, in some cases, the new growth appears to be setting new buds somewhat normally even though this year's growth itself is often twisted and distorted. For comparison, see Picture 6 for what normal bud set and shoot growth should look like in spruce. If affected shoots remain alive and mature normally the rest of this season, next year's growth may very well be O.K. even though this year's twisted and distorted shoots will still be evident. In more severe instances where the new shoots along with the needles have already begun to turn brown and there appears to be little or no bud development occurring, (Photo 7) shoots are unlikely to survive. Where these symptoms are widespread on the tree, if it does survive, any remaining landscape value would appear to be unlikely. (Photo 8).
A third question on many people's minds is "Is there anything I can do to help save the tree or reduce the damage?" At present there are varying opinions as to what the best cultural practices are to minimize or reduce the impact of current injury as well as reduce the probability of further injury. For now, it seems that preventing any additional stress to the trees would be beneficial. For example, watering to avoid additional drought stress on the tree, while at the same time being careful not to overwater the trees, would be prudent.
Because much is still unknown about this unfolding and expanding situation, the Minnesota Department of Agriculture is currently collecting information from University of Minnesota Extension, DuPont, EPA, commercial lawn care applicators, and other state departments of agriculture to assess the scope of this issue. You can visit the Imprelis page on the MDA's website. See their official statement on the situation at this time and how to contact them with damage reports. Also, there is currently a good summary article by Dr. Peter Landschoot from Penn State University regarding the characteristics of this herbicide and the impacts they're seeing on affected trees. You can access it via Penn State University Extension.
As symptoms continue to develop and further assessment of survival is documented there will likely be other articles on this situation, I'm sure. Stay tuned!
Robin Trott, UMN Extension Educator
The hot humid days of summer have arrived, and with them, that childhood favorite, Antirrhinum majus, the ubiquitous snapdragon. Called a "calf's snout" for the flower's snout-like shape, the botanical name Antirrhinum is Greek for "like" and "nose." The specific epithet name majus means large. Hand a child one of these flowers, and the first thing they do is pinch the sides to move the petal "jaw". Not many flowers evoke such whimsical childhood memories like the snapdragon. These prolific annuals come in every color but blue, and start easily from seed.
Snapdragons are most productive in full sun (6-8 hours a day), but can tolerate some light shade. Plant in well drained soil, and amend sandy or heavy soils with organic material: compost or peat moss. The root system is shallow and fine, and can be easily damaged by cultivation. Surround plants with a deep layer of organic mulch to conserve soil moisture, prevent weeds and keep the root system cool. Snapdragons need frequent watering for the first couple of weeks after transplanting (daily watering in sandy soils). Once established, water when the top 1" of soil feels dry to the touch. Snapdragons perform best in cool weather, and most cultivars can tolerate frost and an occasional light freeze.
There are many distinctive types of snaps for different uses in your garden design. Trailing plants are a perfect addition to container gardens. Dwarf plants have a dense, bushy habit producing numerous flower spikes. They grow just 6 to 15 inches tall and are perfect plants for use in a low border or containers. Mid-sized varieties grow 15 to 30 inches tall and are used in borders (either alone or with other annuals). Tall varieties will grow 30 to 48 inches in height, and are perfect for the back of your flower border.
For cut flowers, choose tall varieties and plant at 4" spacing. These tall snapdragons need support to grow straight. Stems are geotropic, which means that tips will bend up if stems aren't vertical. Wind, rain and the weight of the plant itself can cause twisted growth in unsupported plants. These curves will remain, even if the plant is later straightened vertically. Use stakes, peony rings or horizontally staked mesh netting to support plants as they grow. Mesh sizes of 4"x4" or 6"x6" are most commonly used. Two levels of support netting are standard. Place the first level of netting 4"-6" above the ground, and the second level of netting 6" above the first level. Raise the second level as the stems lengthen and strengthen.
Harvest your snaps during the coolest part of the day when flowers on the lower 1/4-1/3 of the spike are open or at least two to five flowers are open per stem.
Some new and unusual varieties of snaps have entered the market in recent years. Butterfly snapdragons are covered with double blooms, reminiscent of delphinium flowers. These dense floral spikes are quite fragrant, and are stunning in cut bouquets. Look for cultivars like 'Madame Butterfly' or 'Chantilly'. Popular tall varieties include 'Rocket', 'Snappy Tongue' & 'Animation'. For the front of your garden bed, look for 'Liberty', 'Tom Thumb' and 'Floral Carpet'. Trailing snaps are ideal for the "spiller" in your container gardens, look for varieties like: 'Cascadia', 'Luminaire' and 'Fruit Salad'.
"Living in that childish wonder is a most beautiful feeling -- I can so well remember it. There was always something more -- behind and beyond everything." -Kate Greenaway
Karl Foord, UMN Extension Educator
Most apples trees today consist of an upper part, the scion, and a lower part, the rootstock, to which the scion has been grafted (Exhibit # 1). The scion produces the apples with which you are familiar such as Honeycrisp or Haralson. The rootstock confers a number of important traits on this 'compound' plant such as precocious flowering and size reduction. A tree on its own rootstock would produce a full sized 25' high tree and could take 6 to 7 years to flower. A dwarfing rootstock can reduce the size by 50% or more and reduce the time to flowering to 2 or 3 years. Size reduction makes more efficient use of space and facilitates numerous operations such as picking, pruning, and spraying. Rootstocks confer other traits on the plant such as disease resistance, stress tolerance, and ability to tolerate low
Thus apple breeding and improvement efforts must not only create and test scions for fruit quality and disease resistance, but also create rootstocks that have the desired dwarfing qualities, cold tolerance, and favorable reaction with the scion. To this end many rootstocks have been created with different degrees of dwarfing. The standard is a tree on its own rootstock which will be a full sized tree. Dwarfing rootstocks are classed by the percent reduction in size conferred by the rootstock relative to a tree on a seedling rootstock (Exhibit # 2). The size variation can range from a tree you could grow in a large pot on rootstock P22 to a full sized tree on a seedling rootstock. Exhibit #'s 3 and 4 show tree size variation conferred by three commonly used rootstocks.
All well and good but how is such a tree produced? A bud from a cloned version of the original tree is T-bud grafted on a cloned version of the original rootstock. In August a dormant bud in the axil of a leaf from the scion say Zestar!TM is harvested from trees pruned in such a way as to produce a lot of these kinds of buds. A T shaped cut is made on the rootstock tree about six inches above ground level, and the bud is inserted to pair the cambium cells of both materials. The cut is wrapped with a paraffin tape and left to overwinter. In the spring when the bud breaks the rootstock tree is cut above the graft and the scion becomes the upper part of the tree. This process is described in greater detail with very illustrative pictures in the following document: http://www.kuffelcreek.com/GrowingApples/GraftAppleOrchard.pdf
The rootstock is also produced in a fascinating way. A cloned rootstock tree is planted and allowed to grow for a season and then is cut off at ground level. The next season a number of sprouts will arise from the rootstock and have the appearance of a bush. These branches are then mounded with sawdust covering around 10 inches of the new stem. The stem will develop roots between the uncovered part of the stem and the covered part still attached to the stump. At the end of the season the sawdust will be removed and the stems cut from the stump and the new shoots with roots will be planted as a new tree ready for the T-bud graft. These mounded layers are called stool beds.
If you go to buy an apple tree, purchase one where the scion and rootstock are both identified on the plant label. It used to be that the label on apple trees for sale would only indicate the scion and not the rootstock. At a big box store, I recently saw trees with labels that only indicated that it was a fruit tree. The label did not even identify the tree as an apple let alone as a Honeycrisp on M26. There is a big difference between Zestar!TM , Honeycrisp, and Haralson apples and as you now know a big difference between the rootstocks on to which they are grafted. To purchase a tree labeled in this fashion would be like buying a pepper plant and then waiting to see if it was a sweet bell pepper or a jalapeno.
All exhibits created by Karl Foord.
Spiders have been very common in and around homes lately. One type that has been particularly conspicuous is fishing spiders. Fishing spiders belong to the family Pisauridae (which also includes nursery web spiders). They are the largest spiders in Minnesota with a body length up to one inch long. Including the legs, they can be as large as several inches across. They are sometimes confused with wolf spiders to which they are very similar in appearance.
Fishing spiders are generally brownish and can have stripes on the body and chevron markings on the abdomen. However, color is not a good method to identify fishing spiders. You can partly do it by size. Another way is to look at the eyes. Like other spiders, fishing spiders have eight eyes which are arranged in two rows of four. As you look straight at the face of a spider, the bottom row (called anterior eyes) is straight or slightly upturned while the top row (called the posterior eyes) is strongly curved. The center two eyes of the top row (called the posterior medial eyes) are little larger than the others.
Fishing spiders are associated with water, such as ponds or lakes, where they feed on a variety of insects, as well as tadpoles and even small fish. They capture prey by sitting on aquatic vegetation or surfaces near water and wait motionless with their legs outstretched for something to swim by. Although they don't construct webs, they do use their silk to attach several leaves together to form a nursery for the egg sacs. Although you typically find fishing spiders near water, one commonly encountered species, Dolomedes tenebrosus, can be commonly found 100 yards or more away from water.
Despite their size, fishing spiders are not aggressive to people and rarely bite (and if they do, it is typically because they are mishandled or feel threatened, like getting accidentally trapped under clothing). Any bites do not hurt any worse than mild bee stings. There is no need to control fishing spiders. If you find one outside, just ignore it. If one accidentally enters your home or other building, just capture it in a jar and release it outside.
What's wrong with my plant?" tool on UMN Extension Website
This time of year, a multitude of plant problems become very visible in gardens across Minnesota. Insects, diseases, wildlife, environmental and cultural problems can all cause garden plants to look less than their best. In order to determine the best management practices to bring plants back to healthy vigorous growth, gardeners need to know what's causing the problem in the first place.
The University of Minnesota Extension Horticulture team has developed a user friendly online diagnostic tool called 'What's wrong with my plant?' located on the Extension Garden page. Following simple steps, gardeners are able to narrow down the possible problems based on the symptoms they are seeing. Once the pest is identified, a link is provided to a publication describing the pest and management options.
Planning a trip to the Minnesota Landscape Arboretum? Check out the calendar below to see what's in bloom!
Yard and Garden News Editor: Karl Foord
Technical Editor: Bridget Barton
Michelle Grabowski, UMN Extension Educator
M.Grabowski, UMN Extension
Photo 1: Rotten strawberry with characteristic dusty gray spores of gray mold
As the new crop of strawberries is being harvested, many gardeners may be dismayed to see that their long awaited berries have spots of soft brown rot, often covered in dusty gray spores. The source of the problem is a common fungal pathogen known as Botrytis cinerea, or gray mold.
Gray mold is prevalent this year because of the cool wet weather in Minnesota during the days that the strawberry plants were flowering and growing green fruit. The gray mold fungus thrives in high humidity and temperatures between 59 - 71F. The longer the leaves of the plant stay wet, the more likely the fruit are to rot.
The gray mold fungus survives from year to year in old plant debris. Fungal spores form on old dead leaves and are blown onto the strawberry blossoms.
Gray mold reduces the strawberry crop in two ways. Often one or more flowers within a cluster will turn completely brown and dry up, never producing fruit. These flowers are victims of blossom blight. In some cases the gray mold fungus infects the flower but does not cause blight. Instead the fungus waits until ripe fruit develops. It then infects the fruit and causes soft brown rot to form. As the fruit ripens, the rot spreads until eventually the entire fruit is rotten. If left on the plant, this fruit may become a dry brown mummy berry. Most fruit rot starts with a flower infection, but fruit can also become infected through contact with another rotten berry, soil or dead leaves. Gray mold can also spread after harvest when a rotten fruit sits in a bowl next to healthy fruit.
The best way to reduce problems with gray mold in a home strawberry patch is to reduce humidity and leaf wetness in the patch and to clean up old infected plant debris. The following steps will help keep gray mold in check.
· When choosing a location for the berry patch, pick a site with good air movement and good drainage. Orient rows to prevailing winds so that leaves and fruit dry quickly.
· Control weeds to reduce humidity and shading in the bed.
· Do not apply nitrogen fertilizer before harvest. This results in a dense canopy that shades the fruit and increases humidity.
· Pick fruit frequently and early in the day. Pick only firm healthy fruit.
· Handle berries with care and refrigerate soon after picking
· Remove infected fruit from the field frequently throughout the harvest season.
· For June bearing strawberries, mow the beds after harvest. Rake up and remove all leaf debris. For more details on renovation of June bearing strawberries read Time to Renovate.
Jeffrey Hahn, Asst. Extension Entomologist
The Asian longhorned beetle (ALB), Anoplophora glabripennis, was recently found for the first time in Ohio, 30 miles southeast of Cincinnati. This exotic borer, originally from Asia from southern China, Korea, and Japan, was first found in North America in 1996 in New York. Two years later it was found in Chicago (but was eradicated there). Since then, it has also been discovered in New Jersey (2002), Toronto (2003), and Massachusetts (2008) before being found in Ohio.
This is a good reminder to be watching for ALB in Minnesota. Although it has not been discovered here yet, we have a lot of trees this borer loves to attack, including maple, American elm, and willow. It is important for people to be familiar with ALB so suspicious insects can be reported. In Ohio, a private citizen found insects in three maples that she thought could be ALB and reported it to entomologist at Ohio State University who then passed this on to USDA-APHIS for verification.
The best way to recognize ALB is from the adults. They are large insects, ranging in size from 1 - 1 ½ inches long (not counting the antennae). Like other long-horned beetles, ALB has antennae that as long or longer than its body, up to four inches in length. ALB particularly has distinctive black and white banded antennae. It's body is a glossy black with as many as 20 white distinct spots on it. Because of this, ALB is sometimes called the starry sky beetle. Adults are active throughout the summer and into the fall.
Don't confuse ALB with the whitespotted sawyer, a native long-horned borer in Minnesota. A whitespotted sawyer is about 3/4 - 1 1/4 inches long and has a dull black body with indistinct white spots or patches. Males lack any banding on their antennae while females possess only faint bands. Whitespotted sawyers are associated with conifers.
You may see ALB larvae in wood. They are legless and cylindrical in shape with a head that just sticks out of the body. They are large, growing up to two inches in size. These larvae create oval tunnels as they bore into the sapwood and heartwood. Although it is easy to identify ALB as a type of roundheaded borer (the larvae of long-horned beetle), it is difficult to identify roundheaded borers as ALB.
If you have maple, elm, or willow in your yard or other hardwoods like birch and poplar, watch for signs of infested trees. Because ALB is such a large insect, when it emerges as an adult, it creates a large, 3/8 - 3/4 inch wide round exit hole in the trunk or branches. This large enough to stick the eraser end of a pencil into the hole. Other potential signs of ALB include sawdust on the ground or the fork of branches, sap oozing from the exit holes, and the presence of small oval to round shallow pits chewed into the trunk or branches - the females chew these for a place to lay eggs.
If you think you have found ALB, contact the Minnesota Department of Agriculture's "Arrest the Pest" Hotline at 651-201-6684 (Metro Area) or 1-888-545-6684 (Greater Minnesota).
Photo 1: Korean Fir Abies koreana 'Horstmann's Silberlocke.' To view all photos, please open PDF.
Karl Foord, UMN Extension Educator
Cones are a big part of the ornamental appeal of evergreens. The cones provide spectacular colors, such as the iridescent cones of the Korean fir (Photo 1), and striking geometric patterns formed by the interlacing scales of red tamarack cones and light pink Acrocona spruce cones (Photos 2 and 3).
To view all photos in this article, please click here: Gymnosperms 7-1-11.pdf
Most but not all gymnosperms have male and female cones on the same tree (Photo 4). The male cones are short lived but the female cones persist for several years. The persistent female cones are the seed bearing structures of gymnosperm plants of which conifers are the most abundant. The word "gymnosperm" comes from the Greek meaning naked seed as opposed to other flowering plants termed angiosperms whose seeds are enclosed during pollination. Conifer seeds develop on the surface of the scales of the cone which open to receive the pollen to fertilize the egg cell and then close to protect the growing seed. Seed maturation can vary from 6 to 24 months depending on species. Most pines exhibit first and second year female cones (Photo 5). When the cone matures in the second year, the scales will separate to free the mature seed (Photo 6 and 7).
These seeds are the edible seeds we know as pine nuts. Worldwide some 20 pine species produce sufficiently large seeds for commercial purposes. The Stone Pine (Pinus pinea) has been the primary source of pine nuts In Europe and was domesticated some 6,000 years ago.
In North America three western pinyon pine species are the main source of pine nuts; Colorado pinyon (Pinus edulis), Single-leaf pinyon (Pinus monophylla), and Mexican Pinyon (Pinus cembroides).
Another fascinating thing about cones is the shape of the interior space between the scales of the cone. This space exhibits aerodynamic qualities enabling the cone to filter large amounts of pollen from the air and deposit them at the most advantageous position for pollination to occur.
I'll never look at a pine cone in the same way ever again.
Robin Trott, UMN Extension Educator
In a few weeks our ditches and roadsides will be full of those yellow daisies known as Black-eyed Susans or rudbeckia. A native wildflower and perennial favorite, rudbeckias are reliable plants that fill our gardens with brightly colored flowers from July through the first frost. They are easy to grow, adapt to a wide variety of soil conditions, have very few insect or disease problems, and bloom the first year when started from seed. However, they weren't always a staple of American gardens.
In the early 17th century, British plant collector, John Tradescant, collected roots from French settlers in the "New World". The plant was shared with other botanists and herbalists, and was soon popular in English Gardens. By the mid-1800's, it found its way into American gardens and was noted by an early garden writer as "the darling of the ladies who are partial to yellow." It was used medicinally by Native Americans to treat both people and horses. The roots and flowers were made into teas and compresses to treat a variety of ailments, including: snake bites, worms, earaches, indigestion, burns and sores.
There are 25 species of Rudbeckia including perennials, biennials and annuals. A member of the Aster family, Rudbeckia's flowers come in single- semi-double and full double forms, and range from lemon-yellow to gold, chestnut, mahogany and bronze as well as multi-colored blooms. If you have never planted Rudbeckia, I encourage you to try some this year. They were stellar performers in our garden last year, and many marginally hardy varieties made it through our snowy winter, and are beginning to bud out. Some varieties I have successfully grown are:
Rudbeckia fulgida is perennial to zone 3. 'Goldsturm' is a 2'-3' tall plant that is long-lived and reliably produces abundant blooms from midsummer to frost. It was voted the Perennial Plant of the year in 1999.
Rudbeckia triloba, the brown-eyed Susan, is hardy to zone 4. Plants are 2'-5' tall, and the flowers are yellow with black centers that fade to brown.
The largest group of rudbeckias is Rudbeckia hirta, or gloriosa daisies. These are short-lived perennials, and are grown as annuals in our northern climate. They readily self seed, and are some of the most colorful Rudbeckia available.
- 'Indian Summer' was an All-American Selections winner in 1995. It produces giant 5"-9" flowers on 3' tall plants. The golden petals are wider than the wild variety, and the flowers make long lasting cuts.
- 'Cherokee Sunset' is a semi-double and double flower, with 2-4" blossoms in shades of yellow, orange, bronze and mahogany. These 2' tall plants are spectacular in the garden and in mixed fall bouquets.
- 'Cherry Brandy' is a 24" single flowering variety. Its long-lasting 4" blooms are cherry red at the tips darkening to deep maroon at the center. This "Susan" has the typical "black eye".
- 'Autumn Colors' is an upright compact plant just 20 to 24 inches tall and 15 inches wide. The Single and Semi-double, 5-7" flowers are a vibrant mix of oranges with deep brown and orange markings.
Rudbeckia make excellent cut flowers, with a vase life up to 21 days. Harvest rudbeckia when the flowers are fully open, during the coolest part of the day, and place in clean, warm water. Re-cut stems under water, removing about one inch, to eliminate air bubbles and bacteria. Create your floral design and place bouquet in water containing floral preservative.
Rudbeckia are ethylene sensitive. Ethylene is an odorless, colorless gaseous plant hormone that exists in nature and is also created by man-made sources. It can be produced by ripening produce, propane heaters, auto exhaust, cigarette smoke, other flowers and fungi. For longest vase life, keep your floral bouquets away from ethylene producers.
Visit your local garden center, or consider purchasing seed next year for beautiful Rudbeckias in your home garden. Whichever you choose, you won't be disappointed.
Jeffrey Hahn, Asst. Extension Entomologist
Immature earwigs were have been seen in gardens recently and will soon turn into adults. Many areas of Minnesota experienced high earwig numbers last year. Be on the watch for them in your garden this summer. Earwigs are about 5/8 inch long, with a flat, reddish brown body and very short wings. They look like a cockroach or a rove beetle but are distinctive because of the pair of pinchers (cerci) on the tip of their abdomen. Nymphs are similar to adults except they are smaller and generally lighter in color.
Earwigs are most active at night and like to hide during the day in dark, tight, damp areas, like under potted plants, cracks between bricks and pavers, and on plants in buds and folded leaves. Earwigs are scavengers, feeding on damaged and decaying plant matter as well as weakened or dead insects and other small organisms. Earwigs can also feed on healthy plant material. This is when they can become a problem in gardens.
Earwigs can damage flowers, like dahlias and marigolds, chewing irregular holes in flower blossoms and in leaves. They are also reported to attack various vegetables, corn silk, and seedlings. Some of this damage can be confused with slug feeding. However, slugs leave a slime trail while earwigs do not. If you are not sure what is causing the damage you are finding, go outside at night with a flashlight check under plants for earwigs and other pests.
To reduce the number of earwigs around your garden, clean up debris that earwigs can hide under, such as leaves, plant debris, bricks, piles of lumber, and similar things. It can also be useful to thin out or remove mulch. You can also set out rolled up newspapers to trap earwigs. Put them into your landscape or garden during evening. In the morning shake the traps above a pail of soapy water to remove the earwigs.
Minimize excess moisture in the landscape. Be sure that the landscape has good drainage and that irrigation systems are working properly. A good strategy when watering is to irrigate more thoroughly and deeply but less often so the surface of the soil remains drier.
You can also protect plants with an insecticide application. An effective method is to treat the surrounding mulch where the earwigs are hiding. Use a drench, e.g. lambda cyhalothrin or carbaryl for this. You may need to attach the product to a hose to get sufficient volume. You may also be able to protect individual plants by applying a spray, e..g. permethrin, deltamethrin, or acetamiprid or a dust, e.g. permethrin or deltamethrin, to plants when damage is first noticed.
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