Yard & Garden Line News March 1, 2003

Yard & Garden Line News
Volume 5 Number 3 March 1, 2003

Features this issue:
European Earthworms in Minnesota
Choosing Houseplant Fertilizer
Approach Glossy Plant Ads With Scepticism
Have Shade Trees and Fruit Trees Pruned Now
This Winter May Hurt Home Garden Fruit Plantings
Snow Cover and Winter Injury to Woody Ornamental Plants
Snow Fleas
Options for Managing Iris Borer Without Cygon
Taking a Liking to Lichens
Editorial Notes

European Earthworms in Minnesota
Lee E. Frelich, Director of the University of Minnesota Center for Hardwood Ecology,
Cindy Hale, graduate student, Forestry
Andy Holdsworth, graduate student, Conservation Biology

Figure 1. Nightcrawler. (Click on image for full view and caption.)
Photo credit: Cindy Hale

What's the big deal about earthworms in Minnesota?

All of the terrestrial earthworms in Minnesota are non-native species from Europe and Asia. (There is a native species that woodcock eat.) At least fifteen non-native terrestrial species have been introduced so far. Studies conducted by the University of Minnesota and forest managers show that at least seven species are invading our hardwood forests and causing the loss of tree seedlings, wildflowers, and ferns.

Why aren't there native earthworms in Minnesota?

We have no evidence that earthworms ever inhabited Minnesota before European settlement. Even if they did, the glaciers killed any native North American earthworms in our region. For the last 11,000 years since the glaciers receded, Minnesota ecosystems developed without earthworms. There are many species of native North American earthworms in such unglaciated areas as the southeastern states and the Pacific Northwest. However, native species have either been too slow to move northwards on their own or they are not able to survive Minnesota's harsh climate.

How did the 15 earthworm species get here?

Figure 2. Redworm. (Click on image for full view and caption.) Photo credit:

The first earthworms probably arrived with soils and plants brought from Europe. Ships traveling to North America used rocks and soil as ballast which they dumped on shore as they adjusted the ballast weight of the ship. During the late 1800's and early 1900's many European settlers imported European plants that likely had earthworms or earthworm cocoons (egg cases) in their soils. More recently, the widespread use of earthworms as fishing bait has spread them to more remote areas of the state. All common bait worms are non-native species, including those sold as "night crawlers", "Canadian crawlers", "leaf worms", or "angle worms".

Much of the bait that is sold contains a mix of species in it. For example, when you buy night crawlers (Lumbricus terrestris) (Figure 1) you also often get , Lumbricus rubellus (Figure 2), one of the most damaging species to the forest floor of sugar maple forests. There are also many species of earthworms (including L. rubellus) available for sale over the internet. Introducing any non-native species-including earthworms--into the wild in MN is illegal.

What are the harmful effects of nonnative earthworms?

Figure 3. Forest without worms and with plants.
Figure 4. Forest with earthworms and without plants

Earthworms are ecosystem engineers. They alter the rate at which nutrients are recycled in the forest ecosystem, and change the physical structure of seedbeds on the forest floor. These are major changes that will cascade through the ecosystem and affect every species of plant and animal in Minnesota's forests. European earthworms will change forest productivity and determine the species of plants and animals that will live in the forest in the future.

Minnesota's hardwood forests developed in the absence of earthworms. Without worms, fallen leaves decompose slowly, creating a spongy layer of organic "duff". This duff layer is the natural growing environment for native woodland wildflowers (Figure 3). It also provides habitat for ground-dwelling animals and helps prevent soil erosion.

Invading earthworms eat the leaves that create the duff layer and are capable of eliminating it completely. Big trees survive, but many young seedlings perish, along with many ferns and wildflowers (Figure 4). Some species return after the initial invasion, such as Pennsylvania sedge (Carex pennsylvanica) and Jack-in-the-pulpit (Arisaema tryphillum) (Figure 5), but others disappear. During the initial invasion, much of the standing crop of plants is killed. Afterwards, those few plants left are subject to grazing by deer, which can lead to complete extirpation of forest herbs within a given woodland. There is then no seed source for the plants to recover, even if they would otherwise be able to recover.

In areas heavily infested by earthworms, soil erosion and leaching of nutrients may reduce the productivity of forests and ultimately degrade fish habitat.

Do all European earthworms species have the same impacts?

Figure 5. Carex. (Click on image for full view and caption.) Photo credit:

Earthworms fall into 3 ecological groups. The epigeic species, are those that live in leaf litter and do not go deep into the soil. They are small and reddish-brown in color, and eat decomposing leaf litter and fungi. Dendrobaena octaedra is one of the most widely spread species in the state. They break up the leaf litter from a solid chunk (mor) to a looser texture (mull). They do not seem to do much damage to native plant species. Dendrobaena is parthenogenetic, meaning it can reproduce and form a population from one individual. This characteristic probably helps it spread rapidly.

Another common epigeic species, Lumbricus rubellus (Commonly called "red worms" or "leaf worms", Figure 2), actually consumes the duff layer quite fast when it invades. This species has been shown to contribute to the disappearance of native plant species, especially the endangered goblin fern (Botrychium mormo) (Figure 6), but it is likely that other species such as bellwort, trillium, blue and yellow violets, spikenard and bloodroot are greatly reduced in abundance when this species invades (Figure 7). Of particular concern are species that rely on associations with fungi, and species that depend on decaying duff, such as coral root orchids.

Several endogeic species of worms, often called "angle worms" (Figure 8), live in the soil and rarely come to the surface unless it is dark or rainy. This group includes the narrow-bodied species Apporectodea rosea, which is pale in color with a bright pink head at one end. It is very common in city lawns and shows up on sidewalks after the first warm rain in spring.

Figure 6. (Click on image
for full view
and caption.) Photo credit: (copyrighted) Steve Mortensen

Figure 7. Bloodroot, bellflower and spikenard. (Click on image
for full view
and caption.)

Figure 8. (Click on image
for full view
and caption.) Photo credit: Cindy Hale

There is one anecic, or deep burrowing species in MN-the night crawler-Lumbricus terrestris (Figure 1). Night crawlers can go up to 6 feet into the soil, and they primarily eat fresh leaf litter that falls to the ground. In many hardwood forests, night crawlers consume most of the leaves that fall in October by mid-summer, leaving the soil exposed to the erosive action of rain drops.

Aren't earthworms good for soil and gardens?

It depends. Earthworms create a soil of a certain consistency. For soils that are compacted due to heavy use by agriculture and urbanization, for example, earthworm tunnels can create "macro-pores" to aid the movement of water through the soil. They also help incorporate organic matter into the mineral soil to make more nutrients available to plants. However, in agricultural settings earthworms can also have harmful effects. For instance, their castings (worm excrement) can increase erosion along irrigation ditches. In the urban setting, earthworm burrows can cause lumpy lawns.

Relative to simplified ecosystems such as agricultural and urban/suburban soils, earthworm-free hardwood forests in Minnesota have a naturally loose soil with a thick duff layer. Most of our native hardwood forest tree seedlings, wildflowers, and ferns grow best in these conditions.

The increased bulk density of soils caused by earthworms can lead to less infiltration of rain-fall water, which hits directly on the hardened crust formed by earthworms as they work the soil. This means drier soils and more surface erosion. There might also be more leaching of nutrients.

We have noticed that wildflowers such as trillium do not grow as large and spread as fast in a garden with earthworms as in another garden without them. The high density of the soil when earthworms are present seems to contribute to this problem. There is also evidence that mycorrhizal fungi are less abundant in areas with earthworms, and many North American plant species require mycorrhizae for optimum growth.

If nonnative earthworms are already here, isn't it already too late?

No. Without humans moving them around, earthworms move slowly, less than a half mile over 100 years. If we stop introducing them we can retain earthworm free areas for a long time. Also, there are many other non-native earthworms available for sale that could have even more harmful effects. Even in areas with earthworms already present, we don't want to risk introducing any of these other species.

What about worms in compost piles?

Non-native "red wiggler" earthworms are sold and shipped all over the country for home compost piles and vermicomposting (worm composting) operations. Thus far, they have not been shown to survive Minnesota winters. However, if they or other species are able to survive Minnesota winters and escape from compost piles they could further harm native forests. If you have a compost pile in a forested area, do not introduce additional non-native earthworms. If you are concerned about spreading non-native worms with your compost, you can kill worms and their eggs by freezing the compost for at least 1 week.

Can earthworms be eliminated from forests?

Currently there are no chemical methods. Chlordane was used to remove earthworms from lawns, but is now banned as a toxic chemical.

Preventing earthworm introductions is the best protection. Birds such as robins eat earthworms, but are unable to control earthworm populations. There are some natural predators, such as the New Zealand flatworm, which is causing extirpation of earthworms in their native habitat in England. However, its introduction here is controversial, because it is not known if it would harm other native species.

The pH of the soil and the palatability of the decaying organic matter on the soil surface does influence the abundance of earthworms in your garden. For instance, soils under spruce or pine trees are more acidic and thus have fewer earthworms. This may be a better location for a northern native flower garden. On the other hand, areas under maple and basswood trees have leaf litter that earthworms consume voraciously, thus exposing the bare mineral soil. Since earthworms cannot consume wood chips, they may be a better mulch for native woodland flower gardens with high earthworm populations. This is an important area for future applied research.

What can I do to help?

Don't transplant plants and trees into remote wooded areas where there are not any earthworms at this time. Dump your extra fishing bait in the trash. Remember, anything that moves dirt can move worms, so use good "hygiene" when recreating and traveling through remote areas. Tell others "the dirt" on invasive earthworms in Minnesota.

For more information on nonnative earthworms and other ways to help, visit MINNESOTA WORM WATCH at: http://www.nrri.umn.edu/worms

Choosing Houseplant Fertilizer
Deborah Brown, Extension Horticulturist

Fertilizer burn. Photo credit: Deb Brown

Now that days are growing noticeably longer, it's time to fertilize your houseplants since they're finally coming out of the winter doldrums and starting to resume more active growth. But there's always some confusion about which type of fertilizer to choose. There are so many on the market.

Plants actually make their own food by converting light energy to carbohydrates through the process of photosynthesis. Fertilizer simply supplements this process by providing nitrogen, phosphorus and potassium (and sometimes minor or trace elements) needed for healthy growth.

Organic houseplant fertilizers act slowly because they usually must break down in the soil before becoming available to plants' roots. This means you run little or no risk of injuring your plants when using them, but you won't see results for a while. The cooler you keep your home, the cooler that moist soil will be, and the longer it will take for organic fertilizer to become available.

By way of contrast, inorganic fertilizers are in a form that plants may use from the minute you apply them to the soil. But you must take care to apply them only to soil that is already slightly moist, to minimize any chance of burning. Another way to help avoid burning is to mix houseplant fertilizer half-strength. Labels tend to recommend more fertilizer than is really needed anyway, especially for the less-than-ideal growing conditions encountered by most houseplants indoors.

Approach Glossy Plant Ads With Scepticism
Deborah Brown, Extension Horticulturist

Misleading
strawberries

Bogus bananas

Untruthful tomatoes.

They're starting already! Purveyors of questionable plant deals are busy trying to take advantage of people's thirst for spring planting. Glossy ads compete for our attention with coupons for fifty cents off breakfast cereal or laundry detergent. But most of these plant ads are not a bargain.

Take dwarf banana trees. They're interesting as houseplants, but I've yet to see them produce fruit year-round in a sunny window, as promised in the ads. Maybe in a large greenhouse or conservatory, but not in an average home. Nor can you produce strawberries indoors, "even in winter."

Ditto, tree tomatoes which, according to the ads, are "not to be confused with an ordinary vine or a tomato plant." "...simply stand back and watch your tree quickly zoom to the full height desired and supply you with yummy fresh garden tomatoes." Don't you believe it! If the plants ever do produce fruit for you � and that's unlikely � it will be instantly apparent that they aren't tomatoes at all.

There are many legitimate mail-order (and Internet) nurseries whose reputations are built on years of service. Put your trust in them -- and in local nurseries and garden centers. They know what can be expected to grow well here.... and what can't. The nursery or garden center down the road from you wants to keep your business. They're not about to make up wild claims for plants that are marginally hardy here, at best.

Have Shade Trees and Fruit Trees Pruned Now
Deborah Brown, Extension Horticulturist

The best time to have both shade trees and fruit trees pruned is late in the dormant season, right about now. This timing is particularly important for oak trees. Because of susceptibility to oak wilt disease, oaks should not be pruned between April 15th and the end of June.

Choose your tree trimmers carefully. Ask for references, then check them out to see what kind of work they did. Trees are a valuable asset to your property. Protect your investment in them by having the job done right. Don't even attempt to do it yourself unless your trees are still young (still small) and need minimal shaping.

Though maples and some other shade trees will lose lots of sap at the pruning sites when trimmed now, you needn't worry about them. Nor do you need to apply pruning paint or wound dressing. Sap is mostly water. It will stop flowing when leaves expand to their normal size.

This Winter May Hurt Home Garden Fruit Plantings
Doug Foulk, Regional Extension Educator, Metro District

As of this writing our Minnesota winter of '02-03 is far from over and almost anything could happen. Yet based upon a dry autumn, a cold, snowless first half of winter and a consistently cold, often windy period in late January and early February, home gardeners will want to keep an eye on the following fruit plants:

Winter damage to strawberry field. Photo credit: Emily Hoover

Strawberries: Considering that they grow all the way north to the Canadian border, strawberry plants are not as hardy as one might imagine. Perhaps surprisingly to home gardeners, the flower buds for next year's crop can be damaged by temperatures around 20 degrees above zero! And at a still moderate 15 above, the entire crown can be severely damaged or killed outright. Indeed, strawberry plants survive our harsh winters simply by being so short in stature that they are easily covered by even small amounts of snow. But winter snow in Minnesota is not always a given. This is why we normally recommend that home gardeners cover their strawberries with 4-6 inches of organic mulch once fall temperatures dip into the low 20s.

Strawberry crown injury. Photo credit: Emily Hoover

This year in particular, arctic cold arrived well before the snow. Therefore, if you didn't mulch your strawberry plants last November, do not be surprised if the plants turn out to be dead come spring. Once spring arrives, if your patch seems reluctant to green up, you can test plant health by digging up a sample crown and slicing it lengthwise with a sharp knife. If the interior of the cigar-stub shaped crown is nice and white, the news is good: the plant is alive and should grow eventually. However if slicing yields any brown streaks and/or mushiness, critical portions of the crown have been killed and the remaining plants may not grow well or at all.

Blueberries: University of Minnesota-released blueberry varieties, unlike strawberries, are fully cold-hardy, often tolerating Minnesota's winter temperature extremes. However, the buds on these otherwise hardy plants are susceptible to a phenomenon called "desiccation," or, for the home gardener, "drying out." Winter winds blowing over the surfaces of these buds can dry them to the point that they will not grow the next season. This year we went into winter with drought conditions-in the Twin Cities, for example, some soils were reportedly bone-dry a foot down. The combination of dry soils and cold winter winds could result in some bud death for blueberry plants in exposed sites. If you live in a windy location, consider protecting your blueberry plants in future winters-1/4 inch bird netting has been shown to effectively slow winter winds and reduce the incidence of bud desiccation. Making sure blueberry plants are well-watered going into winter should also help.

Raspberry plants are susceptible to bud desiccation as well, and plantings in exposed sites may be similarly affected by this year's combination of dry soils and winter winds. In general it is best to plant raspberries in a site that is protected from strong winds.

Apple, pear, cherry and plum trees, especially those planted within the last year or two, may be affected by our winter conditions as well. See the Patrick Weicherding article, "Snow Cover and Winter Injury to Woody Ornamental Plants" in this issue for more information.

Snow Cover and Winter Injury to Woody Ornamental Plants
Patrick Weicherding, Regional Extension Educator, Metro District

Winter frost
on tree. Photo Credit: Beth Jarvis

Many area gardeners have been talking about the combination of mid-winter's cold temperatures and lack of snow cover. Some are wondering what effect this will have on the health of woody ornamental plants. To answer this question we need to revisit the weather conditions that occurred in 2002, particularly during the fall and early winter.

Gardeners who tracked Minnesota's weather knew that Twin Cities' precipitation changed dramatically after October 12, 2002, from pretty wet to pretty dry. After the wettest June-through-October in history (wettest in 111 years of modern records, with 29.89 inches, more than 12 inches above normal), the Twin Cities area closed out its driest November-through-January (driest in modern history, with about four-tenths of an inch of precipitation, 10 percent of the normal 3.98 inches) since the advent of modern weather records in 1891. This extended dry period has resulted in little or no snow cover and, perhaps more importantly, low soil moisture. In years when there is little snow cover, soils freeze more deeply making moisture unavailable for uptake by tree and shrub roots. This situation can be particularly important with evergreen species. On bright, sunny days, photosynthesis and respiration takes place. Moisture lost through transpiration can't be replaced via uptake by the roots. The result is desiccation. In addition, dry winds will increase winter desiccation, causing marginal burn and tip dieback on a lot of plants. With good snow cover, the roots of woody ornamentals are insulated and the snow cover provides much needed moisture as it melts on warm days during winter thaws. As an aside, it is interesting to note that studies done on the use of mulch to prevent winter injury of this type are inconsistent. Research suggests that mulch can either increase or decrease the incidence of winter injury, depending on the conditions of the planting site.

Winter injury on junipers. Photo Credit:
Beth Jarvis

Fall and winter precipitation is crucial to having healthy plants in the landscape. During the summer we are clued in to water stress by wilting and drooping leaves. Plants that experience fall and winter drought can't tell us something is wrong until the next growing season when they fail to thrive. Fall and winter drought can lead to root injury or death. These drought-injured plants may not show symptoms of the problem until the next season or even the next year. In fact they may leaf out and flower just fine in the spring, relying on stored food reserves. Once that energy supply runs out plants weaken and start dying back. Even if a plant isn't killed outright, it is made more susceptible to insect and disease attack.

This type of "winter" injury is more common than most people realize in our area. For the past several years, we have been losing many of our shallow-rooted trees and shrubs without identifying the causal agent. This might be attributed to past winter droughts and cold temperatures without the benefit of insulating snow cover. Birches, for example, are particularly sensitive to fall and winter drought. Weakened by this, the birches that weren't killed outright became increasingly susceptible to attack by the bronze birch borer, which attacks and eventually kills weakened birch trees.

Other trees are also susceptible to winter drought damage, especially those with shallow roots systems. They include Norway maple, silver maple, linden, Colorado blue spruce, Norway spruce, and many other evergreens. Shrubs are also vulnerable to winter drought damage, especially those growing up close to the house or in a warmer location. They include junipers and euonymus.

So what's the solution to preventing this type of winter injury? It's simple� water the plants well in the fall up until the time the soil freezes. The soil should be kept slightly moist down to a depth of 18 inches for most shrubs and a depth of 18 to 24 inches for trees. Water only when the air temperature is above freezing and the soil isn't frozen� which isn't usually much of a problem during the fall but can be during winter dry spells. Water early in the day to allow water to drain away from the bases of plants. (Frozen water next to the bark can physically damage trees and shrubs.) Soaker hoses work well for applying the water slowly and where needed.

Keep in mind that even if we do get lots of rain during the fall, shrubs and trees close to the house foundation or located under eaves may still need watering. Located in these areas, they receive little precipitation and they lose more moisture that other plants because of their proximity to the structure and reflected radiation from the walls.

Snow Fleas
Andy Birkey, Entomology Technician

When winter temperatures get warmer and the snow starts to melt, snow fleas, Hypogastrura nivicola, stop hibernating and become active on top of the snow. One of only a few insects active during winter, snow fleas typically appear at the end of the season when warmer temperatures first begin to melt snow. However, they can be seen at other times of the year. For example, they were also sighted this year in mid-January, during a period of unusually warm temperatures.

Snow fleas Photo credit: Jeff Hahn

Snow fleas are tiny insects (less than 3mm long) and are a type of springtail. The name springtail refers to the insect's �spring-loaded' appendage, called a furcula, that they use to hurl themselves 12 inches or more into the air. This resembles the behavior of a flea, although snow fleas are unrelated to true fleas.

A good place to see snow fleas is to look closely at the snow near the base of trees as they climb through breaks in the snow cover. They will appear as tiny, dark colored specks jumping all over the snow. Although they may be found near trees, they do not harm them. They are also harmless to people and pets. Snow fleas only feed on microscopic fungi, algae, and decayed organic matter.

Springtails in general belong to the order known as Collembola (kol-LEM-bo-la). This group contains species with unique characteristics, thriving under unlikely conditions. They are active during the warmer days of Minnesota's cold winters and survive on Antarctica. Some species can even withstand the intense heat near Hawaii's volcanoes. They come in a vast array of colors and some are bioluminescent, capable of creating their own light. It has been suggested that Collembola are among the most numerous organisms on the planet.

Options for Managing Iris Borer Without Cygon
Jeff Hahn, Assistant Extension Entomologist

Cygon.

Dimethoate, sold under the trade name Cygon, was canceled last year. This was a product that was particularly effective in managing iris borers. Some stores still had some stock on hand so you could purchase Cygon and apply it if you could find it. But this product became increasingly harder to find. In a rare instance, you might still find a leftover container of Cygon this spring but you should assume you will not find any. So without this insecticide, how do we deal with iris borers?

There isn't any one product that can replace Cygon but there are several possible options. You can try a type of natural control by using parasitic nematodes, Steinernema or Heterorhabditis. These nematodes are microscopic worms that specifically seek out caterpillars. Apply nematodes when iris leaves are almost fully expanded but before flowering. Repeat the treatment approximately one week later. Nematodes need a moist environment to survive and move. The easiest time to apply them is during a rain shower. If rain isn't in the forecast, water iris before and after applying nematodes.

Another option is spinosad (Bulls-Eye), another less toxic product. Spinosad is metabolite produced by the fermentation of a soil-dwelling bacterium known as Saccharopolyspora spinosa. It has been demonstrated to by very low in toxicity to mammals, birds and fish. Spinosad can be used against pests on many different plants. It is most effective against moths and butterflies, flies, thrips. This product generally has little impact on most beneficial insects.

You may also elect to spray acephate (Orthene), an organophophate with some foliar systemic activity, i.e the insecticide is taken up into the plant's leaves. For either spinosad or acephate, treat iris in the spring when new growth is about four to six inches high. A repeat treatment 10 - 14 days later may be necessary.

Don't forget your nonchemical options. Watch carefully during spring for water soaked streaks which indicate borer feeding. Crush the larvae inside the leaves or remove damage areas. Sanitation is also very important. Clean up and properly dispose of old plant growth in the fall, especially after a hard frost. This removes eggs and minimizes iris borers that can hatch next spring.

Get the low down on this month's insect pests at Insects http://www.extension.umn.edu/projects/yardandgarden/EntWeb/Ent.htm
Taking a Liking to Lichens
Janna Beckerman, Extension Plant Pathologist

Foliose and fruticose lichens. Photo credit: Janna Beckerman

Evolution progresses in ways that boggle the imagination. It was recently reported that a newly discovered dinosaur existed with not two, but four sets of wings. And most of us are familiar with Tyrannosaurus rex, the unquestioningly terrifying "tyrant-lizard king," with puny, somewhat useless front limbs. Although dinosaurs provide us with the most dramatic case studies of adaptation and evolution, all organisms are subject to it. This includes the members of the fungal, plant and bacterial kingdoms. Many scientists view the interaction of plants, fungi and bacteria as a "co-evolutionary arms race." The result of this arms race is that plants often succumb to various diseases, even though "truces" are usually the norm. These truces result in neither organism having the upper hand. And just like in the human world, where mutually beneficial alliances are rare, plants and fungi, in some instances seem to have achieved and perpetuated an ability to happily coexist. One such culmination of this happy co-existence resulted in the development of organisms called lichens.

Lichens are the embodiment of a symbiotic relationship, or 'The living together of different species of organism which may or may not be to their mutual benefit.'. As we all know, organisms can live together in ways that are mutually beneficial (mutualism) or in ways where one organism benefits to the detriment of the other (parasitism).

Lichens are unusual creatures. It may not be correct to truly call them a creature! A lichen is not a single organism the way most other living things are. In fact, lichens are a combination of at least two and sometimes three organisms that live together. The part that provides the food through photosynthesis is an alga or cyanobacterium (formerly called 'blue-green algae'). Most of the fungi that coexist as lichens produce an apothecium, or cup-shaped disc to allow for reproduction.

Crustose lichen. Photo credit: Janna Beckerman

In many instances, the fungus and the alga that compose a lichen may each be found living in nature, mostly microscopically, without its partner-but the beauty that results when they make this alliance is remarkable! Some of the more enterprising fungi have multiple partners, and colonize more than one species of algae or cyanobacteria. However, going back to the peculiar and unpredictable nature of evolution, there are some fungi that are completely dependent on its algal counterpart for survival. Although lichens are often offered up as an example of mutualism, the algae or cyanobacteria get very little out of this relationship. One prominent lichenologist proclaimed, "Lichens are fungi that have discovered agriculture."

I think a more apt description is "Lichens are fungi that have discovered slavery." When examining a lichen, it is clear that the fungal parts exist to provide protection to the food providers of the relationship, the algae or cyanobacteria. As multicellular organisms, lichens are composed of several, specialized parts. The basic lichen "plant body" is called a thallus, which is made up of the fungal counterpart and consists of hyphae. Lichen are composed of a protective layer of fungal tissue called a cortex that protects the algae or cyanobacteria that provides photosynthesis for growth. Below this is a layer of loose fungal thread (hyphae). The fungus provides mineral nutrition by decomposition; the algae or cyanobacteria produce the majority of food.

Crustose lichens Photo credit: Janna Beckerman

Like other organisms, lichens are identified and classified based upon their looks (or morphology). Crustose lichens produce tightly formed, colorful crusts that adhere to fences, rocks, sidewalks and trees. These lichen can't be removed without damaging the substrate. Foliose lichens are as the name describes--somewhat leaf-like. They are relatively loosely attached to their substrates. Perhaps the best known of these unknown organisms are the fruticose lichens, including Cladonia sp., or British soldiers. ( See image at: http://www.twofrog.com/images/britsoldiers.jpg ) . They appear like little shrubs in miniature. They also hang down in long strands from trees. Finally, squamulose lichens have scale-like lobes called squamules that are usually small and overlapping. The base of Cladonia is squamulose, even if the showy part is fruticose. It is important to note that although lichens often live on trees, they do not harm the tree in any way.

It is unknown how many different species of lichen are present in Minnesota. It has been said, and I would agree "Lichens are the most overlooked of the conspicuous organisms in the natural landscape. The eye often cannot see what the mind does not already know." Get to know the lichen. You may take a liking to them!

More about lichens can be found at:
http://users.argonet.co.uk/users/jmgray/links.htm
http://www.lichen.com/
The lichen portrait gallery:
http://www.lichen.com/portraits.html#anchor315751

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

Editorial Notes

Croton. Photo credit: Beth Jarvis

Due to all the copy I had for March, I let two of my "peerless prognosticators" off the hook until April 1. Neil Anderson, Floriculture and Bob Mugaas, Turf Science will give us their opinions on the toll the winter will have on herbaceous plants.

Next month, we return to 2 issues per month, so the April 1 issue will feature Doug Courneya, Regional Extension Educator, Olmstead County talking about buckthorn reduction. For April 15, we'll hear from Gopher State One Call, the service that notifies your utility companies to mark where their buried lines run. It's state law, call before you dig!

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/. Our home page has clickable links to most of the components of the Yard & Garden Line, such as Bell Museum of Natural History, Yard & Garden Clinic, INFO U and the Soil Testing Lab.

If you work for a garden center, tree service, lawn care company, landscaper or other company/organization that has not received our promotional mailing of point of sale material (padded tear off sheets that hang from a shelf bracket, brochures, posters and bookmarks, drop me an e-mail. But first, take a look at what's available at: http://www.extension.umn.edu/yardandgarden/YGLpromos.html. Then, tell me what material you'd like and how many and I'll send it out. There's no charge, of course.

Deb Brown answers gardening questions on Minnesota Public Radio's (MPR) "Midmorning" program on the first Friday of every month at 10 a.m. Katherine Lanpher hosts the program that 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

The Yard & Garden Line, part of the University of Minnesota Extension Service, is a one (toll-free) phone number source for Minnesotans to call for help with many gardening, water quality and wildlife questions. Most of the services are free of charge.

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