Yard & Garden Line News Volume 7 Number 13                                                               August 15, 2005

Features this issue: The New Entrance to the Display and Trial Garden Giant Silk Moth Caterpillars West Nile Virus Alert All the Corn You Can Eat - Free! Wild Cucumber Weed ID 101--American Burnweed August Garden Calendar Editorial Notes

The New Entrance to the Display and Trial Garden
Part II: The Seed of Knowledge
Julie Weisenhorn, Teaching & Technology Specialist - Landscape Program

Photo credit: Julie Weisenhorn

Since our last article about the Display and Trial Garden, we have seen the installation of a new public art piece to enhance the area. Located in front of the Plant Growth Facility and directly across Gortner Avenue from the new Garden entrance is the Seed of Knowledge. Designed by San Francisco artist Seyed Alavi, the 22-foot high sculpture is fabricated out of thick glass panels and painted steel. The seed is tilted backward and is "cracked open" to reveal a live tree growing at its center. Plantings of perennials and ornamental grasses will soon surround the sculpture, repeating textures, form and colors of the upcoming Minnesota Garden design and the landscaping that flows south along Gortner Avenue. The blue of the steel structure will be repeated in various design components of the Garden entrance, and up-lighting inside the seed, a rock mulch path and a larger tree species will be added at a later date to further enhance the artwork.

The Seed of Knowledge adds an exciting and dynamic element to the new entrance to the Display and Trial Garden. The new sculpture creates a focal point for visitors entering the campus from almost any direction, and was featured on the campus tour during the Minnesota Turf and Grounds Foundation Field Day 2005 in July.

"I envision this piece as an homage to knowledge and more specifically to the knowledge contained within a seed that informs the entire cycle of a plant’s growth," says the artist, "Through the analogy of a seed, tree, landscaping, and greenhouse, I hope to portray this magical reality and expose some of its deeper meanings, particularly as it relates to the construct of our socio-cultural paradigm." Alavi developed his idea for the artwork by examining the meaning and concept of the new Plant Growth Facility. He recognized it as an environment like a greenhouse where all the right conditions exist for knowledge to germinate, grow and blossom like a seed. He asked himself questions about plant development and noted that all the information for a plant’s growth and development are entirely contained and concealed within the seed.

Alavi was commissioned by the University of Minnesota Public Art on Campus program at the Weisman Art Museum, through the State of Minnesota Percent for Art Program. The artist was selected by a public art committee comprised of University representatives from areas such as Horticulture, the College of Biological Sciences, and Facilities Management Landcare. The shape, form and materials of the artwork were carefully selected and composed in order to reflect many of the concerns and visions expressed by the students, faculty and staff, and Alavi hopes that somehow the artwork introduces a sense of magic that complements the factual academic studies pursued at the facility.

Giant Silk Moth Caterpillars
Jeffrey Hahn, Assist. Extension Entomologist

Cecropia caterpillar Polyphemus caterpillar Photo credit: Jeff Hahn

It is common during late summer and early fall to find caterpillars on trees or in nearby areas of your yard as they search for a place to pupate. Two of the largest and most striking moth caterpillars in Minnesota are the cecropia, Hyalophora cecropia, and the polyphemus, Antheraea polyphemus.

Both belong to the family of giant silk moths (Saturniidae) and are active as caterpillars from summer into the fall, before they pupate and spend the winter as cocoons. They emerge as adult moths the following spring. Adults are short lived, surviving just one to two weeks, and do not feed. The basically have enough time to mate and lay eggs. These moths have one generation per year.

The cecropia caterpillar grows as large as 4 inches long. It is light green with a double row of reddish orange knobs (turbercles) on the thorax behind the head. There are also series of smaller yellow and blue knobs (turbercles) on the abdomen. These knobs are presumed to be harmless to people. A cecropia feeds on the leaves of many different hardwood trees, including cherry, linden, maple, boxelder, elm, oak, birch, willow, hawthorn, and poplar. The insect constructs a cocoon, often inside a group of leaves, that typically is attached to a branch or to the trunk of the host plant.

The adult cecropia, sometimes referred to as a robin moth, is a spectacular insect, http://www.geocities.com/RainForest/5479/ . It is reddish brown with a wingspan of five to six inches. Cecropia moths are common in states east of the Rocky Mountains.

The polyphemus moth caterpillar grows to be about 3 1/2 inches long when fully grown. It is a pale green with sparse long hairs along the top and sides of the abdomen. These hairs are non-stinging (urticating). A polyphemus feeds on the leaves of many deciduous trees and shrubs, including ash, birch, maple, oak, and willow. It has also been known to eat grape leaves. It forms its cocoon inside leaves on the ground.

The polyphemus moth is a striking brown moth with a large blue and yellow eyespot on each hind wing, http://www.fcps.k12.va.us/StratfordLandingES/Ecology/mpages/polyphemus_moth.htm. A polyphemus has a wingspan of four to five inches and is found throughout most of the United States and Canada.

If you find one of these caterpillars in a tree, do not worry about it. Despite their size, these caterpillars cause little, if any, actual damage to trees and shrubs when they feed. No control is necessary.

If you find a caterpillar or cocoon and are interested to try to rear it to an adult, follow these guidelines. Place it in a wide-mouthed container or a terrarium. Remember that the adult moths can have a wingspan up to six inches and it is important that they have a large enough space so they can expand their wings after they emerge. If you are trying to rear a caterpillar (especially a cecropia), be sure to place a twig or small branch so they can hang their cocoon on it. The adult moths also like to be able to climb up twigs or similar objects after they emerge. Sprinkle the inside occasionally with water to keep it moist and be sure that the container is well ventilated to avoid mold growth. It is best to keep the container in an unheated site. It will have an easier time completing its development and will also emerge in the spring when it can find a mate and complete its life cycle.

West Nile Virus Alert
Jeffrey Hahn, Assist. Extension Entomologist

Photo credit: Jeff Hahn

Much of the information for this article was taken from a news release available on July 26, 2005 from the Minnesota Department of Health. Click on their web site to view the article in its entirety, http://www.health.state.mn.us/news/pressrel/westnile072605.html .

The Minnesota Department of Health (MDH) recently warned residents of Minnesota, especially those in the western and central areas of the state, that they could face an increased risk of West Nile virus. August is already considered the peak month for West Nile virus cases in Minnesota but because of unusually high numbers of Culex tarsalis, an important vector of West Nile virus in Minnesota, the risk is higher than normal.

They point out that the rains of June and the warm weather of July have combined to produced favorable conditions for this mosquito species. These predicted high numbers have been verified through mosquito trap catches. MDH and other contributors, including the University of Minnesota, have reported capturing large numbers of Culex tarsalis in carbon dioxide-baited traps in late July. The trap catches ranged anywhere from several hundred to more than 1000 mosquitoes per trap. These numbers have fluctuated somewhat in early August but are still considered to be high.

Although Culex tarsalis numbers are up, it is not known what the incidence of West Nile virus is. But even if the incidence is no higher than in the past, this still results in higher risk. What is somewhat deceiving to people is the overall number of mosquitoes have declined during July due to dry weather. However, Culex tarsalis survives just fine because it lays a raft of eggs on the surface of water, as opposed to the moist edges near water, like Aedes vexans (our number one biting mosquito species) does. Culex tarsalis is particularly common in open agricultural fields although it is not clear why this is so. A higher percentage of West Nile virus cases also originate from these areas.

People are urged to take the proper precautions to protect themselves from West Nile virus, especially if they are in a higher risk group which includes the elderly and those that are infirm. Fatal cases are more prevalent in people 50 years or older.

* Avoid being outside when mosquitoes are most active, i.e. dawn and dusk.
* If you are outside where you know mosquitoes will be active, wear long-sleeved shirts and long pants.
* Use a mosquito repellent. The most effective choices are products that contain DEET (N,N-diethyl-meta-toluamide), picaridin, and oil of lemon eucalyptus.
* Apply repellents to clothes or skin but only enough to lightly cover the desired areas. Do not overapply repellents!
* Do not treat children with a product containing more than 30% DEET.

You can reduce mosquitoes around your home through the following steps.

* Cut weeds and tall grassy areas near your home.
* Use less attractive lights like sodium lights.
* Leave yard lights off when possible to avoid attracting them unnecessarily.
* Keep window and door screens fitting properly.
* Drain and remove any containers that may hold water (e.g. old tires).
* Keep gutters clean so water doesn't accumulate.

Most humans infected with West Nile virus usually do not show any symptoms or may experience only a mild illness such as fever, headache, and body aches before they recover. Some people also develop a mild rash or swollen lymph glands. However, West Nile virus can have more serious consequences as it cause permanent neurological damage and can be fatal. Encephalitis symptoms include rapid onset of severe headache, high fever, stiff neck, confusion, coma, muscle weakness or possibly death. See a physician if you experience any unusual symptoms.

Get the low down on this month's insect pests at Insects http://www.extension.umn.edu/projects/yardandgarden/EntWeb/Ent.htm
All the Corn You Can Eat - Free!

UMore Park Photo credits: Barb Stendahl

UMore Park in Rosemount will be celebrating its annual Open House on Thursday, August 18, from 4:00 p.m. to 8:00 p.m. with garden tours and classes, tractor-drawn hayrack tours of University research and lots of children's activities.

Have you seen the U's insect collection, birds from the Raptor Center or the Master Gardener Education and Research Display Garden? Winner of the 2005 International Master Gardener Search for Excellence Award, this six acre garden features nearly 50 separate plots, including the colorful Ball Seed Trials of 2006 annuals, history in the heirloom flower and vegetable gardens and even a living willow fence. University of Minnesota grape introductions will be featured at the free wine tasting booth. Clear your calendar now for your visit to the UMore Park Open House, 1605 160th St. West (C.R. 46) in Rosemount. Go to http://www.umorepark.umn.edu .

Wild Cucumber
Nancy Rose, Regional Extension Educator, Horticulture

Wild cucumber Photos: Nancy Rose

Close-up of flowers

Have you noticed the party decorations along roadsides lately? Those strands of frothy floral garland are actually wild cucumber (Echinocystis lobata), a native vine that can be considered a weed or a wildflower, depending on one's perspective.

Wild cucumber is an annual vine that scrambles up and over objects with the help of curling tendrils. You may notice it draped on evergreen trees, laced along fences, and even spreading over tall grasses in fields and ditches. Wild cucumber growing among crops can be a problem for farmers since the vines can tangle in harvesting equipment.

Wild cucumber becomes very noticeable when it blooms in late summer. The small, starlike white flowers are either male or female. Male flowers are borne in showy upright panicles, while female flowers are borne in small clusters. Fertilized female flowers develop into small, fleshy, oval fruits covered with soft spines. The bright green leaves of wild cucumber have a distinctive star shape with 5 to 7 lobes.


[Ed. note: the Yard &Garden Brief on wild and bur cucumbers is on line at: http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/h524cuke-wild-bur.html.]


Weed ID 101--American Burnweed
Beth Jarvis, Yard & Garden Line

American burnweed Photo: Beth Jarvis

Niger thistle flowers Photo: Hans Kandel

A couple of weeks ago, a gardener here at the Arboretum brought me some weeds to identify. The most interesting of the lot is one I've seen a couple of times but never had a name for it. Now I do and so do you. It's American burnweed or fireweed, Erechtites hieracifolia. Apparently, it gets its common name because it moves into burned over areas. It looks like wild lettuce or some kind of not-very-prickly thistle.

Someone thought it was Niger thistle, but Hans Kandel, Regional Extension Educator, Crookston, has done research on Niger thistle, the stuff of finch feeders. He said it wasn't Niger thistle. Niger thistle seed from India or Ethiopia is sterilized to prevent germination, but apparently some does manage to germinate when it falls below a bird feeder. He sent jpegs of the plant both with and without flowers. I think the flowers are gorgeous, so I've included them at left for you to see.

Eventually, my jpegs found their way to the U's Herbarium and that was how the identification came to be. In a Google search, I discovered burnweed has another common name, pilewort, and that it is listed in the Peterson Field Guide to Wildflowers. When it blooms, it has white flowers that look like groundsel.

August Garden Calendar
Compiled from conversations with Bob Mugaas, Nancy Rose, Patrick Weicherding, Regional Extension Educators

Lichens on paper birch. (see * below) Photo credit: Beth Jarvis

Trees and Shrubs:

Now you can start fertilizing trees with slow-release fertilizer. Research has shown that the only nutrient trees respond to is nitrogen, so sulfur-coated urea and similar high nitrogen products can be used.

You can certainly plant trees and shrubs now, so have fun at plant clearance sales!

Research shows that fall-transplanted trees might not redevelop a functional root systems in time to survive the winter. This is because freshly dug material loses a significant percentage, up to 90% of its root system when dug. In the spring, these freshly dug plants have all summer to regenerate their root systems.

According to foresters, transplanting a tree means one is dug out of the ground in which it was originally planted and replanted with roots and soil intact, such as tree-spading. Planting refers to trees or shrubs that were planted into containers as smaller plants that have been growing in that container long enough to have developed a fully functional root system and that root system is relocated intact into the planting hole.

Regardless of when you plant, water all trees and shrubs regularly for at least 5 years.

If you're thinking about planting "something" next spring, now is a great time to research finding the right tree for your site.

*Read about lichens at:
Yard & Garden Brief on lichens http://www.extension.umn.edu/projects/yardandgarden/ygbriefs/p429lichens.html

"Taking a Liking to Lichens"--Y & G Line News article, from March 2003:
http://www.extension.umn.edu/yardandgarden/YGLNews/YGLN-Mar0103.html#lichens

Lawns:

Now is a great time to do over-seeding and re-seeding. We're in the prime 3-4 week period because of warm soils for faster germinations, less competition from weedy grasses that can come in and usually, we get a little more rain. Days are getting shorter and temperatures are cooler which is good for growth of cool season lawn grasses.

Sodding is less timing sensitive.

First weekend of Sept. is an appropriate time for first application of fertilizer. Water it in by applying 1/4-1/2" of water. Continue to apply water if we don't get at least 1" of rain per week, because grass is actively growing it needs water.

If lawn has become dormant, start watering to get plants growing and apply the first fertilzer when plants show signs of renewed growth. You want the plants to use the fertilizer that is available.

Core aerating and dethatching/vertical mowing can be done near the end of August. Aerating is easier on the plants as it slices holes in the soil. Aerating is especially necessary in compacted soil, especially if there's traffic. Dethatching is harder on plants as it cuts through runners between the plants.

Now is the time to do lawn repairs, as you have the entire fall to get lawn establish before winter.

Kill weeds 7-14 days before you plan to seed. Again, if the lawn adnd weeds have gone dormant, they need to be revived to be actively growing so they can take up the herbicide.

Fruits, Flowers and Veggies:

Annuals such as petunias will continue to bloom until frost if the spent flower heads are removed (deadheaded). This means pinching off the spent flower to ther stem behind the flower itself. Petunia seed pods look like small acorns, with slightly pointed end.

Pick basil before it flowers.

Keep watering garden plants. The have the greatest need for wqhater when producing fruit. Blossom end rot, common on peppers and tomatoes, is prompted by erratic watering.

Be sure to keep potatoes out of the sun while curing and hill soil over any that appear at soil surface level. Potatoes are stems modified for starch storage so when exposed to light, tubers will turn green from chlorophyl production. Light also prompts the production of two alkaloids--solanine and and chaconine. Small amounts of these alkaloids impart a good flavor to potatoes but too much can make you ill. The alkaloids are concentrated under skin so peeling the potatoes will rid the green potato of most of the alkaloids.

Where possible, leave tomatoes attached in clusters or with a bit of stem attached. This reduces the exposed area where molds or bacterial could enter the fruit and hasten deterioration. Tomatoes with stems that readily detach at the "knee" in the stem are called jointed tomatoes. This "knee" is where the fruit pedicel abscission zone is located. Commercial tomatoes are bred to be jointless, where the entire stem stays attached as the abscission layer doesn't form and tomato clusters stay intact.

Last August's garden tips are at: http://www.extension.umn.edu/yardandgarden/YGLNews/YGLN-Aug1504.html#tips

Editorial Notes

A Duluth garden. Photo credit: Beth Jarvis

There are approximately 45-60 days left to our growing season in southern Mn. I expect a killing frost in my suburban garden in early October. The folks who garden in Duluth and parts north of the TC might not have that. The photo at left was taken at a friend's garden yesterday.

Carl Rosen will discuss planting garlic in the Sept. 1 issue. Bob Mugaas' article on the changing face of garden herbicides will appear in the September 15 issue. This is the companion of the lawn herbicide piece. Bob's asked me to post a slightly modified version of the lawn herbicide article on the web. The revision will appear in a day or two at: http://www.extension.umn.edu/yardandgarden/YGLNews/YGLN-July0105.html#lawncare

On October 1, Patrick Weicherding will write about on-going research at the U that's evaluating whether butterflying, scoring or teasing apart circling roots in container-grown trees makes a difference in the establishment of trees. With the October issue, we return to monthly publication, around the first of the month.

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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