Yard & Garden Line News April 15, 2004

Yard & Garden Line News
Volume 6 Number 5 April 15, 2004

Features this issue:
Shopping for Shrubbery
Why Are My White Pines Red?
What's That in My Garden?
April Garden Tips
Editorial Notes

Shopping for Shrubbery
Nancy Rose, Regional Extension Educator

Author completes planting pine. Photo credit: Nancy Rose

In the spring, a young man's (or woman's) fancy lightly turns to thoughts of ...shopping at the garden center! In addition to the irresistible flats of blooming pansies, you may be thinking of more substantial additions to your landscape. You've had the whole winter to stare out the windows at your yard, and perhaps you've noted where a nice shade tree or a cluster of blooming shrubs would fit perfectly. Spring is an ideal time to get planting, so let's consider what you'll want to look for when you hit your local nursery or garden center.

You'll generally find trees and shrubs available in three forms: bareroot, B&B (balled and burlapped), or in containers. There are advantages and disadvantages to each form. Some things to consider for each:

Bareroot
As you might suspect, the roots of bareroot plants are, uh, bare. Bareroot trees and shrubs are usually harvested in the fall by undercutting the roots, then lifting the plants and removing all the soil from the root system. These plants are then stored over winter in controlled climate facilities where the temperature hovers slightly above freezing and the relative humidity is a dense 95 to 99 percent. These conditions keep the plants dormant but moist so the delicate roots don't dry out. In some storage facilities the roots are kept moist by heeling in with cedar shavings or sawdust.

On the plus side, bareroot plants are often less expensive than container or B&B plants. If you need to plant in quantity (windbreaks, hedges, mass plantings), bareroot plants can be an economical way to go. Plant sizes are generally on the small side, but this is not necessarily a bad thing. In the bareroot harvesting process, a smaller plant often loses a lesser percent of its root system than does a larger plant, and so is in better condition to start growing after planting.

On the minus side, there is a rather limited window of opportunity for purchasing and planting bareroot plants. They are generally available in early spring and should be planted very soon after purchase. The vagaries of early spring weather can make that difficult; if you can't plant bareroot stock right away, be sure to keep the plants cool and the roots moist and well protected. Those bare roots are the tricky part of this form of nursery stock -- if the root system dries out even once, whether in winter storage, at the garden center, or in your car on the way home, the plant can be damaged or killed.

B&B
Like bareroot stock, B&B plants are grown in the ground. But rather than being harvested with all the soil removed, B&B stock is harvested to preserve part of the root system within a volume of soil. The root/soil ball must be carefully carved out by removing surrounding soil without disturbing the ball. The ball is then tightly wrapped with burlap to hold it together during the moving process. If the ball breaks up during the process many small roots may be lost.

The advent of the tree spade made digging B&B stock much easier. Instead of being dug by hand, a tree spade hydraulically pushes large blades into the soil around the plant and lifts out the plant with a cone-shaped root ball. The root balls of tree spaded plants are often held together with a combination of burlap and wire baskets. Giant tree spades can dig trees over 20 feet tall with root balls over 6 feet in diameter. Though it may be tempting to have "instant landscaping" with these large trees, keep in mind that they may have lost 90 percent of their roots in the digging process and it will take years before they start growing again. Small to medium sized trees re-establish much more quickly and are usually a better investment.

No matter what size or how they were dug, the root balls of B&B plants must be kept from drying out. In nurseries and garden centers you'll find the B&B plants thoroughly heeled in with wood chips or other mulch to keep the root balls moist. Look for healthy plants with solid root balls and no signs of wilting. Be sure to keep root balls covered on the trip home from the nursery, especially if you're hauling them in an open pickup truck.

B & B trees. Click image for more pix. Photo credit:
U of Mn
Urban Forestry

B&B plants are more expensive than bareroot, but they are available in larger sizes. Some plants, rhododendrons for example, just can't be barerooted but do fine as B&B. B&B stock also has a wider window of opportunity for planting than bareroot, and can be planted from early spring through early summer and again from late summer through early fall. Another advantage of B&B plants is the soil to soil interface when planting (as opposed to soil to soilless potting mix with container plants), which often encourages faster rooting into the new site.

On the negative side, B&B plants have a lot of their root systems removed in the harvesting process. This means it takes a while for them to re-establish after planting. Because of the volume of soil, B&B stock is quite heavy and can be difficult to transport. Always carry B&B plants by the root ball, never by grasping the trunk (since the unsupported weight of the ball can break off roots.) A two-wheeled cart is very handy for moving B&B plants.

Note: Hand-digging and wrapping B&B plants is a specialized skill. If you want to try it, pick a shrub or small tree in your yard that you won't cry over if it dies. If you need to move a plant that you value highly, consider hiring a professional.

Container
Container grown plants constitute the majority of the plants sold at most garden centers and nurseries these days. Trees and shrubs are available in a range of container sizes from small (1 gallon, also called #1) up to large (25 gallon is about the largest that most nurseries carry but specialty growers may have even larger sizes). Specialized potting media, usually soilless, are used for container plants. Media components usually include some combination of composted bark chips, peat moss, perlite, vermiculite, and sand. Container plants are generally easier to move and easier for nurseries to take care of than bareroot or B&B stock.

True container grown plants have spent most or all of their lives in containers. They may have been up-potted (moved to a larger container) several times along the way. A good container grown plant will have a dense root system that spreads throughout the potting medium in the container but is not root-bound (roots cramped, tangled, and circling around the bottom of the container).

Be aware that you may also see plants in containers that aren't true container grown plants. These plants, sometimes identified as "potted plants", are really bareroot plants that have been potted up in the spring for ease of maintenance and handling at the nursery. The roots of these plants are not well established in the potting medium. Treat "potted plants" much the way you would bareroot plants. Before you purchase a tree or shrub in a container ask if it is container grown or freshly potted. If in doubt, ask someone on the staff to gently pull the plant out of the container so you can examine the root system and see how well the root ball holds together.

Container grown stock has a number of advantages for consumers. Many, many species and cultivars of trees and shrubs, both deciduous and evergreen, are available in containers. These plants are often available in more than one container size, also, so you can choose a smaller but less expensive version or a larger, pricier model. Container grown plants have a very wide window of opportunity for planting, from early spring to mid-fall for most plants.

There are also a few potential negatives for container plants. One is that issue of becoming root-bound in the container. If the roots have been circling madly in the bottom of the nursery container it can be difficult to get them to start growing in a normal outward manner when planted into your yard. The fact that these plants are grown in porous, lightweight, soilless potting media can add to the problem - - the roots may continue to circle around in this light mix rather than push into the native soil, especially in heavy clays. Pruning off circling roots, cutting a few vertical slices along the root ball, thoroughly loosening the soil surrounding the planting spot (try for an area 3 to 5 times the diameter of the container), and spreading the roots as you plant can help overcome these problems. Remember to water newly planted container stock frequently, since that potting mix will dry out faster than the surrounding soil.

Note: Proper planting depth is critical to long-term success for all types of nursery stock. The first roots should be just below the soil surface when you finish planting. For B&B and container plants you may need to excavate a little around the base of the trunk to find where the first true roots are.

Go Shopping!
Now you're ready to be a savvy shopper for trees and shrubs. Do a little research before you go so you know the names of the species or particular cultivars that you're looking for. Smaller specialty nurseries are often the best source for more unusual plants, but you may also find some real goodies hidden behind the masses of junipers at larger chain nurseries. Happy Spring and Happy Gardening!

Why Are My White Pines Red?
Janna Beckerman, Extension Plant Pathologist

Clusters of conifers displaying winter damage, Spring 2004. Note: The most severely affected tree has a canker at its base.
Photo credit:
Janna Beckerman

Winter often gets blamed for the majority of plant deaths in Minnesota. And many people are blaming our real zone four winter for the red foliage covering our white pines across the state. Even though our winter was cold, blaming winter's coldness for our plant ills is incorrect. The real culprit in this case is the dryness of fall and winter causing the damage instead of severe cold. This "winter drought' affects needles through out the entire tree, causing dessication. Dessication develops when warm air temperatures "trick" the tree into becoming active. As a result, the tree loses water by transpiration. Unfortunately, the roots are still frozen and water cannot be translocated to the foliage to replace the lost moisture. This causes the needles to dry. As the needles dry, they turn reddish-brown in the early spring .

Although most plants will show symptoms evenly throughout the tree, plants exposed to extreme temperature fluctuations or strong winds, or direct sun from the south or west facing sides, are more severely affected. This results in a pattern where one side is more severely affected than the other. Evergreens in windbreaks, with southern or western exposures, regularly succumb to winter injury every year. In some instances, groups of trees without an obvious exposure show symptoms. These trees are probably predisposed by other stresses , and are unable to tolerate even minor stresses. Winter injury develops every year in these trees. Groups of trees planted too deeply, too closely together, or in poorly draining soils are all susceptible to developing winter injury. Although this year appears particularly bad to Eastern white pine, white- cedar, junipers, yew, and rhododendron are also commonly affected. Non-native conifers, like Alberta spruce, regularly suffer from winter damage.

Alberta spruce showing injury on one exposure.
Photo credit:
Janna Beckerman

It is important to note that winter injury can be misdiagnosed as salt injury. Susceptible plants growing beside high-traffic roads and sidewalks develop injury from de-icing salts when passing cars spray and aerosolize road salt. Trees within 150 feet of a highway can be sprayed by aerosolized road salt. This damage is readily identifiable as de-icing salt damage usually occurs on the side of the tree closest to the road. The symptoms of salt injury decrease the farther the tree is from the road or sidewalk, and with the lower concentration of salt. In many instances, the affected tree must be directly exposed, usually through splash, to the de-icing salt. This produces a pattern where only the exposed side of the tree facing the sidewalk or roadway is affected. Winter dessication injury does not follow this type of pattern and generally occurs evenly throughout the tree, although it may be more severe on southern or western exposures.

The damage that is seen occurs when the salt that lands on needles is absorbed by the plant. When it accumulates to toxic levels, the needle tips are killed. White and red pines are very susceptible to salt spray damage; Scots pine, Norway spruce, juniper and eastern red cedar are moderately susceptible and jack pine, Austrian pine, larch and black spruce are tolerant to salt spray damage.

In addition to directly damaging the needles, salty run-off can directly burn or be absorbed by the roots. The accumulation of toxic levels of sodium can result in burning and browning symptoms on the needles. High concentrations of salts in the soil can alter nutrient availability, modify pH, and produce Pythium root rot favorable conditions.

Prevention

It may look silly, but this tree is loved! Photo credit:
Janna Beckerman

Unfortunately, for the plant that is already turning red, there is little that can be done at this point. However, for future plantings try to:
� Water all plants thoroughly every fall, with special attention to conifers, to minimize winter drought stress.
� Mulch. Mulching insulates the soil, maintains moisture, and allows roots to replace water lost by the foliage. Mulch also insulates against deep frost layer.
� Plant salt tolerant plants in areas where de-icing salt may be used. Most conifers do not tolerate salt well. Some salt tolerant trees can be found at: "Minimizing De-icing Salt Damage to Trees" at http://www.extension.umn.edu/distribution/naturalresources/DD1413.html
� Plant susceptible conifers in sheltered sites which are not exposed to full sun, salt damage, or prevailing winter winds. Alternatively, protect existing conifers with shelters, or "tents" of burlap, wooden or plastic lath (snow fence), pruned branches or discarded Christmas trees, or by wrapping the entire shrub in burlap. Mounding up snow around conifers may protect them from winter damage.
� Anti-desiccant sprays are often promoted to reduce winter drying if applied before the injury occurs. They have not been found to be effective in scientific studies.
� Do not apply nitrogen fertilizer late in the growing season. Nitrogen promotes succulent, immature growth and prevents this growth from becoming dormant. Such growth is very susceptible to frost injury. Do fertilize in early spring to stimulate growth and replace any growth lost due to winter injury.

Contrary to their terrible appearance, affected trees and their new buds are not dead. Resist the urge to prune them or remove discolored trees until plants have had the opportunity to demonstrate recovery. Minnesota conifers are well adapted to long, severe winters, and have adapted to survive this kind of winter injury. It is more than likely your trees are alive, and will survive their embarrassing appearance, even if they have turned red!

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

What's That in My Garden?
Jeff Hahn, Assistant Extension Entomologist

Centipede. Photo credit: Jeff Hahn

As we get down and dirty in the soil as we prepare our gardens for another growing season, we encounter all kinds of insects and invertebrates. An interesting creature that you may find in your garden is the stone centipede. This animal is known to scientists as Lithobiomorpha or stone dweller. This reddish brown invertebrate can grow up to 1 3/4 inches long.

Centipedes are related to insects but are classified as their own separate group. There are some similarities between centipedes and millipedes which are closely related but they are easy to distinguish. First, centipedes have one pair of conspicuous legs per body segment while millipedes have two pairs of very short legs per segment. Centipedes also move quickly while millipedes are slow. Centipedes have flattened bodies with a conspicuous pair of antennae while millipedes possess cylindrical bodies and very short antennae.

Stone centipedes have 15 pairs of short legs. House centipedes, another common type of centipede, also have 15 pairs of legs but their legs are considerably longer. However, our tropical centipede species have 21 - 23 pairs of legs while soil centipedes possess 29 or more pairs of legs. Although centipede means 100 legs, you won't find any with that exact number as centipedes always possess pairs of legs in odd numbers.

The first pair of legs in all centipedes are modified into poison-filled fangs which they use to paralyze their prey, insects, spiders, and other small invertebrates. Stone centipedes generally don't have a good eyesight but will rely on touch to detect its victims. They live in protected, usually moist habitats and are found under mulch, leaves, loose bark, stones, logs, and similar sites. Some stone centipedes can throw drops of sticky material with their back legs at threatening creatures to protect themselves.

Stone centipedes are harmless to people and are rarely found indoors. Just ignore them when you find them in your garden or other places around the outside of your home. Should you find any in your home, physical removal is the only necessary control. Insecticides are not necessary.

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

April Garden Tips
Beth Jarvis, Yard & Garden Line

Compiled from conversations with David Hanson, Urban Forestry; Bob Mugaas and Bob Olson, Regional Extension Educators; and Jim Luby, Fruit Breeder

Hellebore. Photo credit:
Beth Jarvis

Soil Moisture Advisory

According to Mark Seeley, Extension Climatologist, the Twin Cities is short one to one and a half inches of precipitation based on measurements from 1/1/04 to 4/12/04.

But if you go back to July 2003, when the drought started, we are short over 9" of precipitation. Our normal snowfall was enough to recharge the soil surface but didn't recharge the deeper layer. In SE Mn., the Rochester area is 11-12" behind since last July. Spots of NE Mn. are the only one places with nearly enough soil moisture. Last winter, though they had over 110 inches of snow.

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

Fruit:
*Mulch around woody fruit plants. It will help preserve soil moisture.
*You can start removing the mulch from strawberries. Leave the mulch between the rows to reduce weeds and preserve soil moisture.
*Prune stone fruit (plums, cherries, etc.) and pear trees.
*Fertilize any fruit plants, except strawberries, now.
*Dormant oil and lime sulfur (for raspberries) can still be applied if the buds have not yet broken. Don't apply if green tissue is showing.

Lawn:
*Continue raking and cleaning up.
*Don't rake dead grass into street. Collect it and compost or use it as mulch.
*If there's a lot of sand in the boulevard, rake it off.
*There might be salt in the boulevard so water the area thoroughly to dilute the salt.
*Now's a fine time to reseed dead patches in the lawn to repair dog spots and winter injury.

*If you're seeding this spring, use a pre-emergence for newly seeded lawns that contains tupersan to prevent warm season annual grasses like crabgrass. Tupersan has a short residual and is very expensive.
*Phenology for applying pre-emergence herbicide (generally): when lilac flowers show color, forsythia blooms drop, and flowering crabapple flowers just begin showing color.
*Generally, by the time you mow a newly seeded area, you can use standard pre-emergence herbicides.
*Cool season grasses are growing and germinating. If your reseeded last fall and lawn is at least partially established, you can use any standard pre-emergence.
*Broadleaf weed control can be started as soon as air temperatures are consistently 60 degrees.

*Weeds won't die from herbicide if they're under drought-stress/dormant. Water them, then kill them.
*Now is the second greatest flush of growth for turf grass, so be sure the lawn is adequately watered.

Trees/shrubs:
*Avoid pruning trees while leaves are forming and expanding as the trees are putting energy into leaf and wood production.
You can resume pruning in late June-early July.
*Don't prune oaks until July.
*Don't prune honeylocust until August or September to reduce threat of nectria canker.
*Water, water, water.

Vegetables:
*Check your garden tools. Does the tiller work? Sharpen hoes and organize tools. Get the amendments, seeds, etc. together so they'll be ready when you are.
*Get your soil tested. A routine test should be done annually. It takes 7-10 days to get the results and costs $15. You needed do other testing unless the site has a history of nutrient related problems.
http://soiltest.coafes.umn.edu/
*Incorporate phosphorus, potassium and organic matter (compost, composted manure, etc.) prior to seeding or transplanting.
*Only apply lime, gypsum or other pH amendment only if recommended by soil test.
*Wood ash from home heating stoves or fireplaces shouldn't be discarded in the garden. Wood ash makes the soil alkaline, so only use a light layer,if at all.

*Plant cool season crops and, early season greens. Cool season crops include: asparagus, broccoli, cabbage, lettuce, onions, peas, radishes, rhubarb, spinach and turnips/rutabagas.
*Harden off transplants by gradually exposing them, for at least a week, to outside conditions.
*Peppers, tomatoes and eggplant should be kept inside (warm) until mid-May. Then harden off in sunny, warm site. Peppers should go into the garden when the soil and air have completely warmed as they will be stunted if they get chilled.
*Row covers or dark plastic set over unplanted soil will help warm soil and get plants growing more quickly.
Wildlife:

*If you've been bothered by bunnies:
http://www.extension.umn.edu/projects/yardandgarden/AAMG/wildlife/rabbits.html

*Trails in grass are probably voles. For guidance, see:http://www.extension.umn.edu/projects/yardandgarden/AAMG/wildlife/voles.html
Editorial Notes

Tulip fields. Netherlands Photo credit:
Beth Jarvis

I was awed to see fields upon fields of tulips, daffodils and hyacinths growing in Holland just like we raise corn and soybeans here. This was taken just couth of Haarlem, along the "tulip trail".

May is mythbusters month. We'll hear from Mark Seeley as he discusses what happened to a new proposed USDA zone map (and the myth of the TC being zone 5) and other issues. David Hanson, Urban Forester, will bust some pruning myths.

Once upon a time, holes in trees were treated by filling them with concrete. Technology has changed as we've learned that such rigid filling is damaging to the tree. So what's a tree owner to do with that big hole in a tree? In June, Patrick Weicherding will discuss what, if anything, needs to be done with such tree wounds.

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.

The Yard & Garden Clinic closed December 12, 2003 due to budget cuts. Questions from the general public will no longer be accepted. Samples will not be accepted.

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.

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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