Yard & Garden Line News
Volume 6 Number 10                                                               July 1, 2004
Features this issue:
 Irrigation Systems - Think Trickle
Red, White, and Blue Flowers for Independence Day
The Unremarkable Persistence of Dutch Elm Disease
New Pest Wasp Found
Pine Tortoise Scale
An Interesting Caterpillar in Perennials
Don't "P" in the Lake!
Mark Seeley's Weather Notes
July Garden Tips
Editorial Notes

Irrigation Systems - Think Trickle
Bob Olson, Regional Extension Educator, Horticulture

Attach pressure regulator to household water supply.
Admit it. Just a few short weeks ago you were lamenting about how wet it was. "When is it going to stop raining? If it doesn't dry out soon I'll jump off a bridge." Well, now that July is here, and we're entering the rapid growth phase of many of our plants, it's time to talk about irrigation. As temperatures pop into the 90's, some of our high water demanding crops will require as much as 0.3 inches of water per day. That means either Mother Nature supplies the water or you do.

As we look at the frequent tasks involving dragging out the water hoses, consider an alternative system that is much more efficient from a variety of standpoints. One of the best alternatives is installing a trickle system.

Trickle Systems

Trickle systems consist of irrigation lines that deliver a small flow of water (a trickle's pace) at low pressure. This low volume of water allows for very efficient water use compared to a hose or sprinkler system. The low flow trickle is not only more efficient than conventional systems, but also can result in less disease pressure because the foliage is not wetted. Whereas overhead sprinklers and hand watering can lead to wet foliage and soil splashing, trickle systems are essentially free of this unintentional wetting.

Trickle tape has emitters at 8 to 16 inch intervals. These emitters allow for a SLOW trickle of water.
Labor, Labor, Labor

Perhaps the greatest advantage to trickle systems is their tremendous labor savings compared to hand or overhead watering. Once a trickle system is laid in place, all the gardener does is turn on the spigot. No more dragging hoses. No more standing in the garden amidst tall plants, swatting mosquitoes. No more breaking off plants as the hoses drag through the garden. All the gardener does is turn on the spigot and allow the system to SLOWLY dispense water.

It's important to note that trickle systems SLOWLY dispense water over a long period of time. That means that the systems need to operate for lengthy periods of time - often for 8 hours or more at a time. This may sound like a nuisance, but consider the fact that your garden could be efficiently watered while you're gone to work or sleeping comfortably in bed. The SLOW nature of trickle systems also means, however, that your garden won't rebound as quickly as a conventional system if you let your garden get behind on the watering. Of course with a trickle system you don't have much excuse for getting behind. And if you're on vacation for a week, just tell the neighbor to turn on the spigot in the morning and shut it off at night.

Fittings come as “T’s”, elbows, straight connectors. Attach to trickle tape by twisting.
Where to Use

Trickle systems are almost exclusively used in vegetable or fruit gardens, where the straight rows allow for the simplest of installations. They also have been used in perennial borders and blocks, especially if they are connected to one another. Another great use is in hedge or windbreak settings. Trickle systems are not practical in settings where individual plants or gardens are interspersed throughout the yard. They also are not used for lawn applications or solitary shade trees.

Trickle Components

The home gardener does not need to worry about mechanical parts or elaborate equipment. The basic trickle system will require a water source, usually your city water supply or domestic well. However, trickle systems do not require much pressure, so rain barrels or even large pails can be used in certain circumstances. In remote settings trickle systems have irrigated acres of produce in the absence of a pressurized water system as long as the barrels or pails can be supplied with water.

When attached to water, the system pressurizes and begins emitting (trickling) water along the entire system. Each line can be several hundred feet in length.
All Photos: Bob Olson
Assuming you have a water source nearby, most residential systems are supplied by simply attaching your hose to a pressure regulator. The pressure regulator ensures for an even flow of water, and will cost about $20. It's a hard plastic device that will last for a decade or more as long as you don't run it over with the lawn mower.

The pressure regulator is then attached to the actual trickle lines, often called trickle tape. Trickle tape comes in long spools and has emitters that release the water at 8 to 16 inch intervals along the tape. A 1500 foot roll of trickle tape will cost around $35, and can be re-used for several seasons.

To complete the system you will need a series of plastic fittings that are designed to configure your system exactly right for your garden. These fittings last for years, and sell for under $1 apiece.

An important consideration is the ease of installation. The only tool you will need is a scissors. Because the system is under low pressure, all of the fittings are simply hand-tightened. If the trickle tape gets inadvertently cut from an errant hoe, you simply splice the line with one of the handy-dandy fittings, and you're good to go.

The total cost for an average to large vegetable garden will total around $75, but that will provide enough trickle line and other materials for several years. You'll find that this modest investment will pay dividends in the form of more free time to enjoy your garden, and probably, healthier plants.

Red, White, and Blue Flowers for Independence Day
Deborah Brown, Extension Horticulturist

Patriotic planter Photo credit Deb Brown
Due to a very cool, wet spring – it seems like it rained just about every weekend when I wanted to plant – many people are still putting flowering container gardens together. And luckily, most garden centers, and certainly larger farmers' markets, are still amply stocked with colorful bedding plants and perennials.

In recognition of Independence Day, let's consider combining red, white, and blue flowers for patriotic northern gardens. These traditional colors look great in parks, by bandstands and in other public spaces. But red, white, and blue is also a crisp, clean combination that looks terrific in gardens that front an older white clapboard or red brick house with stately shade trees in the yard – and in large container gardens, anywhere.

It's pretty easy to capture a bit of that nostalgic small-town America feeling. Whether you garden in sun or shade, finding a plethora of red and white blossoms poses no problem, they are so common. (Think geraniums, impatiens, begonias and salvias.) But finding TRUE blue flowers can be a little trickier. Many flowering annuals and perennials that we describe as "blue" actually produce flowers that most people would call purple or lavender.

(We're just not very precise when it comes to colors in the garden. In addition to so-called "blue" flowers that are really purple, we have 'Purple Wave' petunias that are really red-violet, and 'Queen of the Night,' a "black" tulip that's really dark maroon. But I digress...)

Now, purple's not a bad thing in a red, white, and blue mix, but real royal blue or sky blue flowers can be breath-taking! Here are a few of my favorites. Chances are, you can still find some of them for this summer. And definitely, for next.

BLUE ANNUALS

Browallia
'Victoria' salvia Photos: Deb Brown
Bachelor's Buttons, also known by their older name, "cornflowers," are usually direct-seeded in the garden. I'm particularly fond of the old-fashioned tall variety, but dwarf-statured bachelor's buttons are also a standout with their clear royal blue blossoms, and they both make great cut flowers for indoor bouquets.

Blue Lace Flower (Trachymene coerulea), is a fascinating annual that should be grown more commonly. It produces large round clusters of tiny powder blue flowers, and looks a bit like a blue version of the wildflower, Queen Anne's Lace. Plants bloom for a long time outdoors and their flower clusters last a long time indoors when cut.

Browallia is a lovely blue-flowering annual that blooms all summer in light or dappled shade. Though available with white flowers, the blue cultivars ('Blue Bells' or 'Powder Blue') are most showy. These too are under-used, in my opinion, as they make fine companions to impatiens. Imagine a shady garden with red and white impatiens and blue browallias for accent.

Lobelia, flowering annuals that are available as small upright plants or trailers come in sky blue, intense royal blue, and blue/white bi-colors. Lobelias are good for full sun or light shade, but they must be kept moist. Sometimes they run out of steam when temperatures get really hot.

Most so-called "blue" Petunias are purple, but there are some cultivars that are very close to sky blue. ‘Blue Wave' is much bluer than ‘Purple Wave,' but is none-the-less a deep, purplish blue.

Salvia farinacea or Blue Salvia will bloom in light or dappled shade, through it grows most vigorously in full sun. Its tall spikes of tiny flowers are a lovely medium, almost "powder" blue.

PERENNIALS

In addition to the sampling of annuals described above, many choice perennials also produce blue flowers. The problem with most perennials, though, is their relatively short bloom time, typically measured in weeks rather than months. You've got to plan carefully if you want to have red, white, and blue-flowering perennials blooming simultaneously. Mixing annuals and perennials makes the job easier.


Delphiniums.
Photo credit:
Deb Brown
Here are just a few hardy blue perennials to try in your garden; they are not suggested for containers in our climate, though, unless you are willing to treat them as annuals.

Siberian Squill – minor bulbs that bloom first thing in spring producing small, nodding bell-shaped flowers, and often spread and naturalize if you allow their leaves and seed pods to mature.

Bearded iris and Siberian iris

Forget-me-nots – hardy to zone two, they reseed freely in light shade

Mountain Bluet (Centaurea montana) – looks like giant cornflowers or bachelor's buttons

Delphiniums – among the best blue choices around, but generally short-lived in our climate. Plant where they're protected from strong winds, and stake them for added insurance.

Balloon Flower (Platycodon grandiflorus) – named for their swollen balloon-like flower buds which open to large star-shaped cups.

Speedwell (Veronica species) – a large group of blue-flowering perennials that produce long-lasting spikes of small flowers and grow in sun or light shade.

(Ed. note: the flowers are all true blue, but they photographed purple.)

The Unremarkable Persistence of Dutch Elm Disease
Janna Beckerman, Extension Plant Pathologist

Early symptoms of Dutch elm disease.
Tree succumbing to Dutch elm disease. Infection began summer 2003. Photos: Janna Beckerman
Obviously, an unexciting headline like the title of this article isn't going to excite you. Contrast that title to the announcement that a dreaded disease has returned to take more victims, like the recent media sources that have reported that Dutch elm disease is back. As an Extension Plant Pathologist at the University of Minnesota working on urban horticultural problems, I must confess shock. You see, I didn't know it had left.

I have diagnosed countless cases of Dutch elm disease. I have performed "drive by" diagnoses on thousands more. What I've discovered is not going to surprise you: Some years are worse than others, and last year was pretty bad, too. In fact, many of the cases we are seeing now actually were infected last year. The symptoms of Dutch elm disease resemble a tree suffering from drought: Leaves on twigs and branches turn yellow, wilt, and begin brown. These symptoms vary from startlingly obviously, with dying branches, wilting leaves and death in weeks, to inconspicuous and easily overlooked when on small twigs-even when standing under the infected tree. Some trees, like my neighbor's across the street, take months, even years, to die. Others succumb in weeks.

When Dutch elm disease was introduced into the United States, it quickly spread across the country, killing hundreds of millions of trees, and costing similar amounts in dollars. Today, many towns still lay claim to an Elm Street, but not any American elms. As one of the last states to experience the epidemic, Minnesota had decades to prepare itself for the eventual spread of the disease, but did very little. Fortunately, some city foresters responded with aggressive management, and have preserved the legacy of the American elm. Fergus Falls boasts retaining 70% of its original American elm tree population. Regular examination and prompt removal of infected trees prevents the infestation by elm bark beetles that spread this disease. It also prevents the disease from spreading root-to-root between trees. Early diagnosis also provides homeowners with the option to treat infected trees. Two fungicides are labeled for use of Dutch elm disease infected trees: Arbortec and Alamo, and both must be applied by a licensed professional (Fig. 3). Early diagnosis and treatment have a high rate of success, and trees are provided with two to three years of residual protection by these fungicides.

Dutch elm disease isn't back. It never went away, and unfortunately, it never will. Like a wildfire, it continues to smolder, and sends up occasional bursts, but nothing to rival the original conflagration. Although weather conditions certainly play a crucial role with the current disease flare-up, budget cuts, and the layoff of city foresters have literally added fuel to the fire. Misguided and misinformed urban planning commissions and parks boards with limited budgets plant one type of tree, be it the soon to be doomed green ash (emerald ash borer), Colorado blue spruce (really a short-lived perennial in Minnesota), or the borderline hardy Norway Maple, creating monocultures instead of urban forests, setting the stage for future epidemics.

Elm treatment requires a licensed professional. Photo Credit: Chad Behrendt
And make no mistake: The future epidemics are coming. In the last four months, one of the largest nurseries in the country accidentally shipped plants throughout the United States that were infected with the pathogen that causes sudden oak death. This disease has been shown to infect and kill our native Northern red oak and pin oak, in addition to infecting 60 other plant species, with new species added monthly. Emerald ash borer has become established in Michigan, and is spreading. Asian longhorn beetle, which feeds upon maples, elm, birch, willow, and poplar, has been found in New York, New Jersey, and Illinois. And every year, the gypsy moth expands its range, moving closer and closer to Minnesota. All of these pests have the potential to alter not only our landscape, but our ecosystems. We know these problems are coming. The question remains: What will we, as a state, do to prevent it?

Please check out the new diagnostics web pages at
http://www.extension.umn.edu/projects/yardandgarden/diagnostics/


New Pest Wasp Found
Jeffrey Hahn, Asst. Extension Entomologist
John Luhman, Minnesota Dept. of Agriculture

Polistes dominulus between 2 native wasps, P. fuscatus
Native paper wasp.
Photos:  Jeff Hahn
Vertical P. dominulus nest.
P. dominulus nest in fence
pipe. Photos:
Gene White
A new wasp species has been found in Minnesota. John Luhman discovered a Polistes dominulus worker in St. Paul at the Minnesota Department of Agriculture Biocontrol Facilities on June 11. He subsequently found another worker on June 22.

Originally from southern Europe and northern Africa along the Mediterranean as well as in China, this insect is unofficially referred to as the European or Mediterranean paper wasp. P. dominulus was first found in the U.S. in 1981 in Cambridge, Massachusetts and has since spread west to Wisconsin and as far south as Virginia. P. dominulus has also been found in the west in California, Washington, and Colorado within the last several years.

P. dominulus is related to native paper wasp species such as P. fuscatus (northern paper wasp). There are some important differences between P. dominulus and our native species. Although P. dominulus possesses the typical slender paper wasp body and long legs, they are smaller than native paper wasps, about 1/2 inch long compared to almost 3/4 inch long.

What is striking when you first see a P. dominulus is that it is colored much more like a yellowjacket with its black and yellow striped abdomen. It also has two small yellow spots near the base of its abdomen. Although native paper wasps have black and yellow abdomens, they are less striking than yellowjackets. Native paper wasps also have two red or yellow spots at the base of their abdomens which yellowjackets lack.

You can also identify P. dominulus from its nest. A typical paper wasp nest is attached to horizontal surfaces generally out in the open, like under eaves and decks. The cells are exposed (not surrounded by a papery envelope like a yellowjackets' nest). P. dominulus makes a similar nest that can also hang straight down, but their nests are frequently built at an angle of 90 to 180 degrees to the ground. This allows them to occupy sites that other paper wasps would not consider.

These wasps are also more likely to nest in void areas. They are very alert to people and other animals that approach their nest from a range of 12 - 20 feet away. Fortunately, unless you are just a matter of inches away, they seem less like to sting than other paper wasps. Interestingly, while paper wasps (and yellowjackets for that matter too) do not reuse old nests in the spring, P. dominulus will reuse and expand old nests.

P. dominulus are very successful in areas they occupy. They are a couple of reasons for this. They are active earlier in the spring than other paper wasps allowing them to get a head start on nest construction and obtaining prey. Paper wasps generally predate on butterfly and moth caterpillars. P. dominulus also feed on caterpillars but will attack a variety of other insects giving them a competitive edge.

We would be very interested to learn of other sightings of P. dominulus in Minnesota. If you encounter wasps or nests that you believe are this species please contact Jeff Hahn (612-624-4977) or John Luhman (651-282-6809).

Pine Tortoise Scale
Jeffrey Hahn, Asst. Extension Entomologist

Pine tortoise scale Photo credit:
Jeff Hahn
A common scale insect on pine is pine tortoise scale. The adult is not actually seen as it hides under a waxy covering. This covering is reddish brown with black markings, semispherical or helmet-shaped, wrinkled in appearance, and about 1/4 inch long. Pine tortoise scale are found on many pines including Scotch, Austrian, red, and jack pine where they are clustered together on branches. Like all scales, they feed on plant sap with piercing sucking mouthparts. As they feed, they secrete large amounts of honeydew, a sugary substance they are unable to digest. Trees covered with honeydew often result in sooty mold, a black growth. Infested branches take on a dark appearance. Often, this is the first clue that a tree may be infested with scale. Although unsightly, this fungi is not harmful to pine and treatment is not necessary. The presence of honeydew also attracts wasps, ants, and other insects. Pine tortoise scale overwinter as fertilized adults. They finish developing in June and then lay eggs. These eggs then hatch during late June or early July into tiny reddish yellow crawlers. These immature crawlers immediately disperse and begin feeding. Eventually they settle down, mature and mate. Females double their size before overwintering.

Small to moderate numbers of pine tortoise scale usually have little or no impact on tree health. Light infestations can be ignored. Predators and parasitoids (parasites) are present that will help keep populations in check. Do not make unnecessary insecticide applications in order to preserve these natural enemies.

As scale numbers increase, needles can become yellowed and stunted. Severe infestations can slow growth, cause branch dieback and even kill trees. Young, recently transplanted trees are most susceptible, although mature trees can also be injured. If treatment is needed, it should be aimed at the vulnerable crawlers as adults are not susceptible to insecticides. Crawlers first appear sometime during late June to early July.

You can determine when crawlers are active by monitoring trees for their presence. You can shake branches that have scale insects while holding a white sheet of paper or paper plate underneath. If you see tiny reddish or yellowish insects, you have found crawlers and it is the right time to treat. Examine branches on a regular basis starting in late June. You can also place double-sided sticky tape on the branches near females. When eggs hatch, some of the crawlers will become stuck in the tape, making it easier to see that they are there. Place tape on branches in late June and check the tape regularly for the presence of crawlers.

When crawlers are present, there are a number of insecticides that are effective against them, such as permethrin, cyfluthrin, and carbaryl. If you are interested in a less toxic product, try insecticidal soap. Keep in mind that this has no residual activity and sprays needs to be repeated to get good results. You can also apply a horticultural oil to suffocate the crawlers. Another option is treat pine tortoise scale in the fall or early spring with a dormant oil application.

An Interesting Caterpillar in Perennials
Jeffrey Hahn, Asst. Extension Entomologist

Checkerspot caterpillar. Photo credit:
Jeff Hahn
An interesting caterpillar was reported this spring feeding on a number of different perennials, including coreopsis, Rudbeckia, New England aster, and Echinacea (coneflower). These caterpillars were first reported during early June, although they probably hatched sometime in late May. The caterpillars feed until mid-June when they pupate. They are expected to emerge as adults later this summer.

These caterpillars grow to be a little over an inch long. They are black with tufts of spines on each body segment. As they grow larger, they develop a tannish stripe down the sides of their body. Although a pest in your garden, these caterpillars grow up to be an attractive nymphalid (brush-footed) butterfly, probably a species of checkerspot butterfly. In most cases, feeding in gardens is not severe and you can ignore small or moderate numbers.

If caterpillars are abundant, they can cause significant defoliation. If you need to manage these caterpillars, you have several options. You can handpick them and toss them into a bucket of soapy water. Although the spines are dangerous looking, they are not irritating to the touch. You can also apply an insecticide if necessary. There are many contact products that would be effective. Examples of less toxic options include, insecticidal soap, Bacillus thuringiensis, and spinosad. Treat as soon as you notice the caterpillars when insecticides are generally more effective and to minimize plant damage.

Get the low down on this month's insect pests at Insects http://www.extension.umn.edu/projects/yardandgarden/EntWeb/Ent.htm


Don't "P" in the Lake!
Ron Struss, Regional Extension Educator, University of Minnesota Extension Service

Sweep up grass clippings Photo credit:
MN OEA
In Minnesota, summer is short and water is the place to be. Unfortunately, the condition of some of our lakes and rivers makes them unattractive summer retreats. Excessive growth of pea soup green algae takes them off the "beach to be at" list and reduces their enjoyment for boating and fishing and for shoreline hiking and biking.

The cause of excessive algae in our lakes and rivers is the plant nutrient phosphorus. Phosphorus is needed for algae growth but naturally is in limited supply in lakes and rivers. A little bit of phosphorus goes a long way - one pound of phosphorus can stimulate up to 500 pounds of algae growth. If only our financial investments yielded as well!

Nature is stingy with phosphorus, but we humans are generous to a fault. Every time it rains, phosphorus washes off the landscape from our everyday activities. Common sources of phosphorus include grass clippings and tree leaves left in the street, soil eroding from construction sites and bare patches in yards, and waste from our pets and urban wildlife. Until the Minnesota Phosphorus Lawn Fertilizer Law was passed, misapplied and over-applied lawn fertilizer was also a source of phosphorus.

If not cleaned up or contained, these sources of phosphorus wash into the street, down the storm sewer, and into our lakes and rivers. Storm sewers, which are very efficient in preventing street and parking lot flooding during rainstorms, are also very efficient in carrying pollutants that wash off the land. What makes it to the street very quickly also makes it into our lakes, rivers and wetlands.

Every lake, river and wetland has it own area of land that contributes runoff water to it. These areas of land are called watersheds, and the health of a lake, river or wetland depends on the types of human activity taking place in its watershed.

Since human activities are the source of phosphorus and other pollutants that wash off into our water, it takes action on our part to keep water clear. Here are some simple and straightforward steps you can take to be a "watershed steward":

Use the right fertilizer. Photo credit:
MN OEA
Sweep and rake: Keep grass clippings, tree seeds and leaves out of the street. Sweep and rake your curbside clean. If you have a yard blower, blow clippings back into the grass, not into the street!

Pick-up: Clean up after your pets, and never use storm sewers as a place to dump pet waste. In addition to containing phosphorus, pet waste contains bacteria that can lead to beach closings.

Stop soil erosion: Whether we are managing a large construction site or just our yards, it is our responsibility to keep soil from washing away during storms. Keep soil vegetated, and when left bare, reseed and mulch as quickly as possible. "Blooming boulevards" need to be well-mulched to prevent soil eroding into the street. Construction sites with uncontrolled soil erosion should be reported to your city.

Go phosphorus free: It is the law now to use phosphorus free lawn fertilizer unless seeding a new lawn or a soil test shows need for phosphorus. When buying lawn fertilizer, look for a middle number of zero in the three numbers that show the bag's contents.

Soak up runoff: Storm runoff that is soaked up in the soil cannot carry phosphorus to lakes and rivers. Direct downspouts onto vegetated areas where water can soak in. Reduce the size of paved areas whenever possible and consider constructing a rain garden-shallow depression landscape features designed to collect and soak up runoff water.

Don't dump: Storm sewers are links to nearby water and should not be used for dumping wash water, old motor oil or antifreeze, paint cleaners or pet waste. Washing your car? Wash it on your lawn were dirt and soap can soak in, or take it to a commercial car wash.

In short, be stormwater runoff savvy! Know that storm sewers connect our neighborhoods to nearby water, and only clean water should go down curbside storm drains. For more information on clean water practices, visit the Minnesota Water - Let's Keep it Clean website at www.cleanwatermn.org or contact your city's environmental protection or public works department.

Minnesota Phosphorus Lawn Fertilizer Law Changes on January 1, 2005

P-free fertilizer Photo credit:
MN OEA
The Law: After January 1, 2005, phosphorus fertilizer cannot be used on lawns in Minnesota unless one of the following exceptions is met:

Exceptions: Phosphorus fertilizer can be used on lawns in Minnesota when:
º Establishing a new lawn by seed or sod.
º Soil testing shows need for phosphorus fertilization.
º Fertilizer is applied by golf course staff that have taken state approved training.
º Phosphorus fertilizer was purchased before August 1, 2004 and is used outside of the seven county metro area.

Minnesota law also requires spilled and over spread fertilizer, whether containing phosphorus or not, to be cleaned up immediately.

For soil testing information, contact the UM Soil Test Lab at 612-625-3101 or visit them at the "Yard and Garden" section at www.extension.umn.edu/yardandgarden .

Look for the middle number! A string of three numbers on a fertilizer bag show its analysis - the middle number being phosphate (phosphorus) content. A "zero in the middle" means phosphorus-free fertilizer.

Catalpa flowers are now falling. Photo credit:
Beth Jarvis

Mark Seeley's Weather Notes

Looking ahead 10 days into July, Mark Seeley, Extension Climatologist, says he doesn't see a repeat of last July in the TC metro. Precipitation is predicted for 4 days in the metro.

Southern Minnesota will be wetter than normal. Northen Minnesota, from the Red River Valley into central Minnesota (eg: Crow Wing, Itasca and Koochchiching Counties) will remain dry as the summer storms miss them. Seeley cautions that summer precipitation is extremely difficult to predict.

With our wet spring, we're running 1-3" above normal which replenishes the soil moisture. Creeks and lake levels have been slow to return to the higher normal levels as we still haven't made up for the drought that started last summer.


July Garden Tips
Beth Jarvis, Yard & Garden Line

Tamarisk flowers. Photo credit:
Beth Jarvis
We started this garden checklist/tips a year ago. See: http://www.extension.umn.edu/yardandgarden/YGLNews/YGLN-July0103.html#july

Compiled from conversations with Bob Mugaas and Bob Olson, Regional Extension Educators, Dave Hanson, Urban Forestry

(These recommendation are based on Twin Cities temperatures. Adjust for northern Minnesota..)

Lawns:
If temperatures remain cool, you can still spot-treat broadleaf weeds. (Check the label regarding maximum air temperatures.)

If you've not fertilized since spring, it is ok to put down some nitrogen fertilizer at a rate of 1/2# per 1,000 square feet, which is half the normal rate. Otherwise, do not fertilize your lawn heavily now. The growth rate of temperate-season grasses slows in summer's heat.

Post emergence crabgrass/annual grass herbicides may still be used as the cool weather has retarded annual weed grass growth. They contain DSMA and MSMA which often yellow bluegrasses if applied under high temperatures and dry conditions. Be sure to water you lawn the day before if it's not rained recently.

Hold off another month before taking on any lawn renovation projects. Disturbing the soil surface, eg: for planting grass seed, brings weed seeds up that will germinate readily. If you absolutely must plant, use tupersan, an annual grass pre-emergence herbicide to keep the weeds at bay.

Flowers
Remove faded flowers (deadhead) from peonies, columbine and other perennials so all photosynthates will be preserved for future growth. Otherwise, some will be frittered away on developing unwanted seeds. Deadhead roses and annuals, such as geraniums, to encourage new blooms.

Weed , mulch and water as needed. Plants in bloom use a lot of water, as flowers are mostly water.

Trees and Shrubs:
Water trees! Trees need at least one inch of rainfall each week May through July and a little less in August and September.

Choose a dry day to prune trees. Spores of some tree diseases spread during humid or damp summer weather.

Ease off on fertilizing trees and shrubs by mid-July. They need to slow their growth and start hardening off for winter.

The high risk period for oak wilt has passed. However, there is still some risk, so avoid pruning oaks until fall if at all possible. If you must prune, use latex paint or shellac on the wound *immediately* afterward.

Vegetables:
The vegetable garden is in "weed and water mode". Mulch tomatoes and other plants with herbicide-free grass clippings, compost or straw to preserve soil moisture and break the impact of rain that could splash pathologic fungi from the soil surface onto lower leaves (of tomato plants, specifically).

Side dress vegetables, such as tomatoes and corn, as they begin to set their crops.

Do not apply fertilizer to bone-dry soil without watering it in adequately immediately afterward. An inch of water should be adequate in most soils if you apply granular fertilizer at the recommended rate. Liquid fertilizer and additional watering should equal one inch of water. Inadequate watering can result in fertilizer burn from the high concentration of fertilizer. If you wish to apply fertilizer to the foliage of plants ("foliar feeding") apply a half strength solution as the salt in the fertilizer can cause drying/burning of the leaf margins. The safer option is to apply the liquid to the soil surface.

Tomatoes that are not caged should be pruned and tied as they grow, otherwise they may break during windy weather.

If desired, preventative applications of fungicide to reduce Alternaria and Septoria leaf spots on tomatoes could be started. See the publication "Parasitic Diseases of Tomatoes: http://www.extension.umn.edu/distribution/horticulture/DG1155.html

Fruit:
Prune out raspberry canes as soon as they set the summer fruit crop.

Bird netting can be applied over fruit crops to reduce bird damage.

Keep fruit plants evenly moist, weeded and mulched.

Editorial Notes

Interesting landscape plant Photo credit:
Beth Jarvis
The grounds crew at an unnamed public institution apparently didn't recognize the weed velvetleaf and let it flourish most of one season. A weed is technically a "plant out of place" .

Next issue Anne Gachuhi, a new Regional Extension Educator, will write about perennials for clay soils.

Please feel free to cut and paste any of the articles for use in your own newsletters. All we ask is that you give our authors credit.

Back issues Yard & Garden Line News are on the Yard & Garden Line home page at www.extension.umn.edu/yardandgarden/.

For plant and insect questions, visit http://www.extension.umn.edu/askmg. Thousands of questions have been answered, so try the search option in the black bar at the top left of the board for the fastest answer.

Deb Brown answers gardening questions on Minnesota Public Radio's (MPR) "Midmorning" program on the first Thursday of every month at 10 a.m. The program is broadcast on KNOW 91.1 FM, and available state-wide on the MPR news radio stations.

If you would like to receive an e-mail reminder when the next issue of the Yard & Garden Line News is posted to the web, just send an e-mail to: listserv@lists.umn.edu (note: the second E in listserve is omitted), leave the subject line blank, then in the body of the message, type: sub yglnewslist or to unsubscribe, enter: unsub yglnewslist

Happy gardening!

Beth Jarvis
Yard & Garden Line Project Coordinator


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