Yard & Garden Line News Volume 7 Number 17                                                               November 1, 2005

Features this issue: Disrupting Circling Roots of Trees in Containers Name that Apple! Be Aware of Psyllids on Black Ash November Garden Calendar Editorial Notes

Disrupting Circling Roots of Trees in Containers

Patrick Weicherding, Regional Extension Educator, Natural Resources and Environment

Butterflying.

Slicing

Teasing Photos: Gary Johnson

A standard planting recommendation for container-grown trees that show evidence of circling roots is mechanical disruption of the root ball before planting. Mechanical disruption of circling roots is usually done at planting time by making several vertical cuts down the side of the root ball and across the bottom in a practice known as "slicing" or "slashing." "Butterfly" pruning (splitting and splaying apart the lower two-thirds of the root ball) has been suggested for planting sites with compacted or poorly drained soils. A less destructive mechanical root-disruption practice is to "tease" circling roots from the root ball into the surrounding soil at planting time.

Mechanical disruption of the root ball before planting is recommended to encourage rapid root development into the surrounding soil and to help prevent girdling roots from forming. Girdling roots - roots that compress the woody tissues of another root or stem - may shorten a tree's life by constricting the vascular system and restricting water and nutrient movement. They may also result in root systems that fail to adequately anchor trees in the soil, making the trees more susceptible to windthrow during storms.

Mechanical disruption of circling roots in pot-bound, container-grown trees is a standardized nursery recommendation supported by many Universities and tree care organizations. However, the fact is, there is no strong scientific evidence to support the purported benefits of this practice. The data from research studies in this area are limited and contradictory, conducted primarily using shrubs rather than trees.

In order to test whether or not these treatments really work, the "Root Gang" at the Teaching, Research and Education (TRE) Nursery on the St. Paul Campus of the University of Minnesota designed a study to investigate how various mechanical root disruption techniques affected the ability of a tree to develop a functional root system. (The "Root Gang" is led by Jeff Gillman, Department of Horticulture Science, and Gary Johnson, Department of Forest Resources. It also includes Chad Giblin, Department of Horticulture Science, Dave Hanson, Department of Forest Resources, and me).

The study involved two different species of trees, lindens and willows, and four different treatments (slicing, butterflying, teasing and a control where root balls were not disrupted). The treatments were applied to the trees at random and the trees planted in the spring of 2003. They were allowed to grow in the nursery for two growing seasons (2003-2004) then harvested in the fall of 2004. Following harvest, the root systems were washed clean and examined to see if any roots had "broken out" of the confines of the container-shaped root ball that had originally been placed in the ground.

We expected to see some differences between the trees that were treated and those that were not treated. What we found surprised us. For both the willows and the lindens, trees that did not have their root balls disrupted at all had the most roots extending beyond the original root ball after two growing seasons. The next best result was with the trees that had been treated by slicing followed by the teasing and last, butterfly treatments. These results were somewhat disturbing because they suggest that mechanical root disruption, regardless of the specific technique, is not effective. Later, we found out that other researchers have observed similar results in their work.

Are we ready to abandon the standard root-slicing recommendation based on the results of our research? The answer is probably no. First, in this study we were dealing with severely pot-bound trees that probably would have never made it to market from the nursery. Second, this study lasted for two growing seasons and we don't know how additional years of growth will affect the ability of the roots to grow outward into the soil. Finally, we looked at only two species of trees. It is possible that other species will respond differently. For now we'll withhold judgment on the results of this study but we are starting a new set of experiments to look at additional root-disruptions techniques and how additional growing seasons will affect the growth, root circling, and radial root development of pot-bound, container-grown trees.

Name that Apple!
Beth Jarvis, Yard & Garden Line

MN 1797 Photo credit: Dave Hansen

One afternoon in April, I responded to an invitation from David Bedford, apple breeder, to join a small group at the Minnesota Landscape Arboretum to brainstorm possible names for an upcoming apple release. There were a few plant breeding folk, plus refugees from accounting, Andersen Library and the like–a mixed group.

Bedford explained that apples need 2 names, a patent name and a trademark name. The patent name is used on the patent application but a plant patent is only valid for 20 years. It takes 10 to 15 years for an apple cultivar to become recognized in the marketplace, so 20 years isn’t enough time to develop and protect the reputation of a variety. Once the patent expires and the variety reverts to the public domain, anyone can reproduce the tree and sell it using the patent name. So patent names often tend to be less exciting.

Trademarks can be renewed indefinitely so plants and apples now often have trademark names. These trademark names can be totally non-descriptive such as Jazz™ apple. They can’t be outright descriptive though they can be suggestive, e.g. Pink Lady™ or Zestar!^TM apples A good trademark name is like an advertisement every time it is mentioned.

(For a more complete discussion of plant naming, go to: http://www.ca.uky.edu/HLA/Dunwell/PCPLTPAT.html )

The apple in question has been in the U’s breeding program for 35 years. The reason it’s not been released before now is because it ripens at the same time as many other good varieties -- October 10th. Earlier ripening has been a key feature of more recent releases. But the apple breeders don’t rush apple releases. ‘Honeycrisp’ was 31 years in the making and ’Zestar!’ was 26.

We were each given an apple still known as MN. 1797. It has been released to commercial nurseries who are propagating it and would soon need the final trademark name for their catalogs. The use of the trademark is licensed to the nurseries by the University and royalties paid by growers to the University are important to help fund the breeding and development of future varieties.

The name-suggesting process was done in stages. Bedford provided a set of facts . We tossed out possible names based on the new information and our reactions to proposed names. Then he’d tell us something else, and furiously jot down our comments. Color, flavor, the parentage all took turns at center stage.

The new release is a hybrid of ‘Sharon’ a pretty obscure apple from Iowa and ‘Fireside’. We learned that ‘Fireside’ was named after FDR’s fireside chats. Did you know ‘Connell Red’ is a red mutation of Fireside, genetically identical but with solid red rather than striped skin color? That’s why ‘Connell Red’ and ‘Fireside’ can’t be used to pollinate each other.

MN 1797 is a smaller apple than ‘Fireside’ or even ‘Honeycrisp’. Being a good size for a portable snack is something in MN 1797's favor. Bedford sees it as a tasty regional apple though probably not the international superstar that ‘Honeycrisp’ has become.

Apple flavor is based primarily on the amount of sugar and acid. ‘Haralson’ is a tart apple. ‘Honeycrisp’ is considered a balanced apple, equally acidic and sweet. ‘Red Delicious’ has very little acid. MN 1797 has a bit more sugar than ‘Honeycrisp’. It has fuller flavor–‘rich’ was the term used, coupled with an unusually white flesh that is a bit less likely to oxidize after being cut.

Bedford pointed out that a handful of finalist names will be subjected to careful legal searches in an attempt to find existing trademarks that might be similar. This is to avoid potential legal challenges by other trademark holders and to avoid selecting a name that might be confused with other products – apple or otherwise. For example, Zesta was the trademark name first considered for the cultivar now marketed as Zestar!^TM apple. However, the company producing a soda cracker marketed under this fanciful name threatened legal action claiming potential confusion. Mindful of these legal concerns, we pointed out any possible conflicts between proposed names and other products on the market .

He then shared some of the names he and his colleagues had been mulling. Ours would be added to their list. The final decision is theirs. After all, parents get to name the baby.

Apple Update

SnowSweetTM. Photo credit: Dave Hansen

MN 1797 has its two new names !! MN 1797 will be marketed as SnowSweet^TM apple. The patent has been filed using the cultivar name ‘Wildung’ in recognition of Professor Dave Wildung’s years of service to the University and to fruit growers and horticulturists in in Minnesota. Wildung has been challenging fruit plants of all descriptions to grow in northern Minnesota for decades. His office and trial plots are located at the North Central Research and Outreach Center in Grand Rapids. He was honored at a recent University of Minnesota Board of Regents meeting for his contributions.

Three possible names were submitted for trademark searches by University attorneys and the name SnowSweet^TM was found to have the fewest potential legal challenges. SnowSweet^TM trees will be available to commercial growers beginning next spring and fruit should begin to be available from local orchards four to five years later. For those who would like to taste this new apple before it is available at local orchards there will be limited quantities for sale at the Arboretum Apple House next October.

Be Aware of Psyllids on Black Ash
Jeffrey Hahn, Assist. Extension Entomologist

Cottony ash psyllid Photo credit: Justin Knott ND Dept. of Ag.

Psyllids, also known as jumping plant lice, are insects with piercing-sucking mouthparts related to aphids, leafhoppers, and cicadas. They are small insects, measuring between 1/16 - 1/8 inch long. They have four wings held tent like over their abdomens, strong back legs, and resemble cicadas or aphids. Psyllids feed on plant sap.

In Minnesota, we are most familiar with two species of psyllids in the landscape, Pachypsylla celtidivesicula and P. celtidismamma. These psyllids are gall makers on hackberry producing hackberry nipple galls and hackberry blister galls. However, this year a different psyllid species was found in the landscape. A little known insect known as cottony ash psyllid, Psyllopsis discrepans, was discovered attacking black ash, such as ‘Fall Gold' and Manchurian ash.

The history of this psyllid is interesting. It is has been found on limited basis in North America. Originally from Europe, it was first found on this continent in Nova Scotia in 1921. It was next discovered in Michigan in 1955. More recently it was discovered in Edmonton and Calgary in 2000 where it has been a significant pest. It was found this year for the first time in North Dakota, scattered in a variety of places throughout the state.

This psyllid was first identified in Minnesota in 1993. It has been of little consequence in Minnesota's landscapes since it was found here 12 years ago. However, this year, there were reports of this insect in the Minneapolis-St. Paul area as well as in greater Minnesota. We would not consider what we saw a significant population but this insect did seem more common this year than in the past.

The biology of cottony ash psyllid is not well known in Minnesota. Based on what has been reported in other areas, this psyllid overwinters as eggs on twigs, hatching the following spring around bud break. The immature wingless nymphs start to feed on the leaves, causing them to distort. At first, leaves fold over along the edge of the leaflets. Later in the season, the tips of the leaflets can blacken, while the leaves shrivel up. Psyllid nymphs exude a white, waxy material while feeding inside the leaflets.

Psyllid damage Photo credit: Jeff Hahn

This damage is not necessarily live-threatening to trees. A healthy mature ash can tolerate damage from the feeding of this insect in a single season. In fact, foresters in Alberta have discovered that black ash that were well-watered tolerated psyllid damage more easily than drought-stress trees. However, if an tree is attacked repeatedly over several years, it can be weakened and even killed from cottony ash psyllid feeding.

Eventually the nymphs mature into adults which are usually present during June. An adult cottony ash psyllid is small, about 1/10 inch long, yellowish with black markings on its body and has clear wings. This psyllid is reported to have two generations. The second generation nymphs feed inside leaflets damaged by the first generation psyllids as well as along the midrib of unaffected leaflets. It is possible that three generations could occur in Minnesota.

Don't confuse this damage with ash leaf curl aphids. Both insects distort ash leaves and produce white waxy threads. However, when ash leaf curl aphids damage ash, the leaves form more into a ball than cottony ash psyllid damage. Also cottony ash psyllids are not known to attack green ash which is the tree most commonly attacked by ash leaf curl aphids.

And you also shouldn't confuse this insect with emerald ash borer. This beetle is an exotic borer that attacks all species of ash. It kills trees with dieback starting at the top and working its way down. Ash trees are killed within two to three years after they are first attacked. So far, emerald ash borers have only been found in Michigan, Ohio, and Indiana.

If you have a black or Manchurian ash that has been attacked by psyllids remember it is important to keep the tree healthy, especially by keeping it well-watered. If you are still concerned about its health, you might consider protecting your tree from psyllids with an insecticide spray. Keep in mind that this insect is not common in Minnesota and damage has been minimal to date. If you do wish to spray, the best time to treat would be during spring when the leaves are first expanding. Use a foliar systemic insecticide, such as acephate.

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

November Garden Calendar
Compiled from conversations with Bob Mugaas and Patrick Weicherding, Regional Extension Educators

Fall color. Photo credit: Beth Jarvis

Trees and Shrubs:
It's too late to plant trees and shrubs.

Remember, the soil is very dry under trees so if you have a grouping of evergreens, the competition for water is fierce. Make sure they get some extra water.

Mulch the root zones of all woody plants. Put down woodchips three inches deep but 2-3 inches away from any smooth-barked trunks. Mulch will help insulate the soil in case of no snow and retains soil moisture.

Winter protection for newly planted and smooth barked trees and shrubs should be on by Thanksgiving. Tender-barked trees need rodent protection and sun scald protection/tree guards. That stretchy tree wrap is no longer recommended. Use plastic tubes with ventilation holes or tie boards to the south-southwest side of the tree. Hardware cloth cylinders will keep voles and rabbits from chewing up shrubs. Have the task done by Thanksgiving.

Lawns:
Lawn care season is essentially over, except for mowing. Your mulching mower will recycle tree leaves back into the soil. You shouldn't see clumps of leaves on the lawn. If you do, rake them up and compost them.

Dormant seeding of lawns can still be done. You need to spread the seed over a prepared area then rake it to provide good soil to seed contact.

Fruits, Flowers and Veggies:
November tasks remaining are primarily cleaning up garden debris and structures and cutting back perennials. You may leave some perennials, such as stonecrop/sedum for winter interest but anything left over winter can be a bigger chore to clean up in the spring.

Rake up and remove windfall fruits. If you don't plan to use them, compost them or put them in the trash.

Cover strawberries when the ground begins to freeze. Use straw or similar material.

Make any season end notes in your garden journal.

Editorial Notes

Frosted 'Blue Clips' campanula Photo credit: Beth Jarvis

This issue was published late due to some computer problems.

In an upcoming issue, Nancy Rose will talk about plants for winter interest.

Before spring, Bob Mugaas will provide the data from the two year perennial evaluation program that he, Janna Beckerman and a host of Master Gardeners conducted.

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/.

Deb Brown answers gardening questions on Minnesota Public Radio's (MPR) "Midmorning" program on the first Friday 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. (Scroll down for map.)

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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