Submitted by: Mary Blickenderfer and Eleanor Burkett, University of Minnesota Extension Educators

Curly leaf pondweed is an exotic rooted, submersed aquatic plant, similar in appearance to many native species of pondweed commonly found in Minnesota lakes and streams.

Identification

Curly leaf pondweed can be distinguished from other aquatic plant species using the following two attributes:

1. their leaves attach to the stem in an alternate pattern (typical of pondweeds), and
2. the summer leaves have finely serrated margins (only found in curly leaf pondweed)

In addition, the leaves are very wavy and may be reddish in color, but these are not unique to curly leaf pondweed.

Habitat

Curly leaf pondweed is considered a deep-water plant, but will also colonize in shallow water. In a lake where it is dominant, it may start in 1 to 2 feet of water and extend out to depths of 10 feet or more. Because it can toleratie low light curly leaf pondweed grows well in disturbed sites and can grow under algae blooms or ice.

The strong rhizomes anchoring the plants into sediment allow curly leaf to grow in areas with strong wave action or streams with moderate velocity.

Life cycle

Curly leaf pondweed also has a unique life cycle, which gives it competitive advantages over many other aquatic plants.

As the water cools in autumn, it sprouts from buds on small dormant stem structures (called “turions”) lying on the lake bottom. The small winter plants remain alive under the ice and snow. When the ice melts and water temperature warms in the spring, it begins a period of rapid growth of summer leaves. Mats of these leaves may float at or near the water surface.

Later in the spring, flower spikes are produced that emerge above the water surface. By June, the fruits are mature on the stalks and drop to the sediment. The seeds in these fruits have very low germination rates.

Prior to dying back in mid-summer, curly leaf pondweed produces large numbers of small turions in leaf axes along its stem. When the parent plant dies, these living turions disperse by water movement, sink to the lake bottom, and lie dormant during the summer when other aquatic plants are actively growing. Reproduction of curly leaf pondweed is primarily through these turions.

Curly Leaf Pondweed Look-alike: Potamogeton richardsonii (Richardson’s pondweed)

Compare Richardson’s pondweed and curly leaf pondweed using these descriptions and illustrations below. Use this information to distinguish between these plants.

Comparison between Richardson’s pondweed and Curly leaf pondweed.

References:

• Boorman, S., Korth, R. & Temte, J. (1997). Through the Looking Glass: A Field Guide to Aquatic Plant Management.Wisconsin Lakes Partnership.
• Crowell, W. Curlyleaf Pondweed: New Management Ideas for an Old Problem. Minnesota Lakes Association Reporter 7:1.

Submitted by: Emily Wolf, Regional Extension Educator, U of MN Extension Service, (218) 998-5790

One hundred people got more out of this winter than snow shoveling. They attended Curly Leaf Pondweed Management workshops focused on aquatic plant ecology, curly leaf identification, management techniques, and local field experiences.

Lake association members, individual lakeshore owners, and others who attended possessed various levels of knowledge and experience with curly leaf pondweed. All attendees found a review of aquatic plant ecology and identification of this plant beneficial. Of particular use were the presentations of both mechanical and chemical plant management techniques. Advantages, disadvantages, and costs were described, which allowed each lake association or individual to choose the solution that best fits their situation. The workshops also gave participants a great opportunity to network with others tackling the curly leaf problem, allowing additional contacts to be made and information exchanged. Overall, people gained a greater understanding of the complexity of curly leaf pondweed and that there is no “magic bullet” that will eliminate the need for control.

The workshop was a successful collaborative of multiple groups including the University of Minnesota Extension Service and Water Resources Center, MN Sea Grant, Initiative Foundation, MN Department of Natural Resources, and the MN Lakes Association. Several other organizations also played important roles such as the Sauk River Watershed District, Morrison County Planning and Zoning, aquatic plant management professionals and area lake associations.

Please visit the website, or contact a Regional Extension Center for more information.

Morrow Honeysuckle is an invasive plant similar to our native honeysuckles.

Mary Blickenderfer, Regional Extension Educator, University of Minnesota Extension Service, (218) 327-4616While common and glossy buckthorn get most of the attention and bad press for their large-scale invasion and ultimate destruction of native plant communities, Eurasian honeysuckles are in the same league. Most aggressive in our area are tartarian honeysuckle (Lonicera tatarica), Morrow honeysuckle (Lonicera morrowii), the hybrid of these two species (Lonicera x bella), and amur honeysuckle (Lonicera maackii). In addition to these shrubs, the Japanese honeysuckle vine (Lonicera japonica) was “introduced (with good intentions but disastrous results) from southern Asia, now in many places an aggressive vine that defies eradication, forming dense tangles that overwhelm the native (or other) vegetation” (Voss 1996). Control of these honeysuckles requires laborintensive mechanical (pulling, mowing, burning) or chemical (herbicide) treatment. Mature shrubs should be removed first, followed by ongoing treatment of the seedlings that may re-sprout from roots or germinate from seeds in the soil.

In contrast to their European cousins are several honeysuckles native to our area, none of which are aggressive invaders. Bush-honeysuckle (Diervilla lonicera) and glaucous honeysuckle (Lonicera dioica) occur in woods and thickets throughout Minnesota. Fly honeysuckle (Lonicera canadensis), hairy honeysuckle (Lonicera hirsuta), northern fly honeysuckle (Lonicera villosa) and swamp fly honeysuckle (Lonicera oblongifolia) occur in the northern part of the state.

You may be wondering if you have an invasive honeysuckle in your back yard, and how you tell it from the native honeysuckles. As a general guideline, the non-native honeysuckle shrubs are large (5-12’ high), have opposite leaves, and produce delicate white-pink flowers that become bright red (may be orange to yellow) pea-size berries situated in pairs in the leaf axils (where leaves attach to stem). The native honeysuckles are low inconspicuous shrubs (or vines), have opposite leaves, but produce yellow flowers that become pairs of cone-shaped red berries (Lonicera canadensis), narrow capsules (Diervilla lonicera), or peasize red or blue/purple berries. Consult a plant key or plant expert for positive identification.

One final note: don’t eat the berries of the non-native honeysuckles! They are bitter and some contain an unknown poison that causes violent vomiting and bloody diarrhea (Holmaasen 1989).

References:

• Holmaasen, I. 1989. Traed och Buskar. Stockholm: Interpublishing. 176pp.
• Voss, E. 1996. Michigan Flora. Ann Arbor: Cranbrook Institute of Science. 622pp.

Eleanor Burkett, University of Minnesota Extension Service, Brainerd Regional Center, (888) 241-0720

Fall leaves are valuable to gardeners. Composted leaves keep soil in prime condition for most gardening projects. Follow these tips to optimize leaf composting:

• Use large compost bins, 5 to 6 feet across. This size allows for rapid internal heating of the compost pile, which drives the decomposing process. Smaller bins will be slow to heat and will not be able to maintain processing temperatures through the cold Minnesota winter. Bins larger than 6 feet across may restrict oxygen flow into the leaf pile, slowing decomposition.
• Mix some nitrogen into the leaves as you pile them. Leaves are rich in carbon (which makes for great compost) but are comparatively low in nitrogen (needed to feed decomposing bacteria). Nitrogen could be added as a nitrogen fertilizer or fresh green organic matter. For example, for every four bushels of leaves, add 1-2 cups of lawn fertilizer without any weed killers (such as 34-0-0 or 21-0-0). Or add 1 part leaves with 2 parts fresh grass clippings or similar green garden debris.
• Moisten the leaves as they are piled. Rains will be slow to wet through a leaf pile, and moisture is essential for decomposition.
• Do not turn compost piles in the fall. This allows heat to escape and heat drives decomposition through the winter. Turn compost piles in the spring.
• Leaves can be easily picked up with lawn mowers. However, shredded leaves may over-pack in the compost bin, restricting the oxygen flow needed for decomposition.

With attention to these guidelines, a gardener can produce fall leaf compost ready to use by the following late spring. On its own, a pile of leaves may take 2 to 3 years to decompose. For more information, contact your local Extension office and request the publication, Options for Disposing of Leaves.

For information on making a composting bin, call Info U at (800) 525-8636 and enter code #277, or visit the University of Minnesota Extension Service Web site and type “compost bin” into the search box.

Carol Mortensen, Leech Lake Botanist/Invasive Species Project Coordinator, 218-335-7428

A simple definition of biological control is “the use of one living organism to control another living thing.” Biological control, or “bio-control” for short, is frequently an important component of many land management agencies’ invasive species management plans. Leech Lake Division of Resource Management (DRM) has been using bio-control to manage invasive plants such as purple loosestrife and leafy spurge since 1996. In fact, the DRM received funding through the Bureau of Indian Affairs Noxious Weed Program to build a greenhouse that is used as a regional facility to rear a beetle that feeds on purple loosestrife.

About now you may be thinking, “So what? What do I care about purple loosestrife?” Well, purple loosestrife is just one of about 100 non-native plants that are now found on the Leech Lake Reservation, but it is one of the worst. While it is lovely, and not a problem in its native range of Europe, northern Africa, and Asia, none of its natural enemies are in North America. When it was introduced here, probably early in the nineteenth century in soil used as ship ballast, it found nothing to stop its spread. Spread it did, from New England all across the Upper Midwest, infesting wetlands and shoreland, crowding out native plants and degrading wildlife habitat. On the Leech Lake Reservation it has a foothold on Leech Lake, Cass Lake, Big Lake, Bowstring Lake, and many other smaller lakes, as well as in ditches and wetlands. Unchecked, purple loosestrife can spread and wipe out native plants, reduce open water in wetlands, and possibly reduce wild rice stands.

Releasing trapped beetles into a loosestrife infested area.

Now, back to bio-control. For years, herbicides were the weapon of choice in the battle to control purple loosestrife, but loosestrife was winning. So scientists had an idea. They looked overseas where loosestrife was a natural part of the landscape, and discovered a number of insects fed on the plants and kept them from getting out of control. They figured perhaps some of these insects would work in North America as well. So they started testing them to see, for example, if they used other plants besides purple loosestrife for food or at any stage in their development from egg to adult. This testing went on for years, because the last thing anyone wanted was to bring an insect into the U.S. to control purple loosestrife and discover that— oops!— it also had a taste for soybeans or tomatoes.

Eventually, several species of insects were found that damaged loosestrife but didn’t present a problem to other plant species. One of these, Galerucella calmariensis, the black-lined loosestrife beetle, is the one we raise at the DRM. This beetle is about a quarter-inch long, brown, and has darker lines along the outside edges of its body. It doesn’t bite humans. All it wants to do is eat purple loosestrife, mate, and lay eggs. The adult beetles feed on the leaves of loosestrife plants. They lay clusters of tiny whitish eggs on the stems and leaves, which hatch in about two weeks into tiny yellow caterpillars (larvae) that begin to feed on the leaves and flower buds. The beetles reproduce at a rate of about 100 to one, so when the eggs hatch, the larvae can do a lot of damage to the loosestrife plants. By the time they reach full size (about 5/16 inch) they can reduce the plants to shriveled brown skeletons. The plants can’t make and store as much food in their roots as usual, and over the course of a few years, many die. Larval feeding on flower buds reduces the number of seeds produced, so fewer new plants sprout.

Biological control is not the answer to every weed problem. Only a few species of insects have “made the cut” and been approved by the U.S. Department of Agriculture-Animal and Plant Health Inspection Service for use. No bio-control agents have been found for most invasive plants. However for some, such as purple loosestrife, bio-control works very well and is a state-of-the-art component in an integrated weed management plan, which combines biological control, chemical control, and manual techniques. The insects we use have been rigorously tested, are widely-used across North America, and are no more likely to change their eating habits than are milkweed-eating monarch butterfly larvae. Biological control is also better for the environment, because it reduces the use of herbicides.

Beetle to help control the Purple Loosestrife.

If you would like more information about biological control or invasive species, please feel free to contact me at the DRM. During summer, stop by and visit the greenhouse insect-rearing facility. We’d be happy to give you a tour!

Jil M. Swearingen, National Park Service, National Capital Region, Center for Urban Ecology. March 23, 2004.

What is a Native Species? All organisms are native to planet Earth (until further notice) and each species of bacteria, fungi, plant, and animal has a home somewhere on this planet where it has existed and evolved for thousands of years. A native or indigenous species is one that occurs in a particular place without the help of humans. Species native to North America are generally recognized as those occurring on the continent prior to European settlement.

An organism’s home, or native range, is determined by a host of influences such as climate, geology, soils, hydrology, biological interactions, and natural dispersal. Creatures are dispersed within their natural ranges by various means including air, water, on animals, and during animal migrations.

What’s an Exotic Species? An organism is considered exotic (alien, foreign, non-indigenous, non-native) when it has been introduced by humans to a location(s) outside its native or natural range. This designation applies to a species introduced from another continent, another ecosystem, and even another habitat within an ecosystem.

For example, black locust (Robinia pseudoacacia), a tree that is native to the southern Appalachian region and portions of Indiana, Illinois and Missouri, was planted throughout the U.S. for living fences, erosion control, and other uses for many years. Black locust is considered exotic outside its natural native range because it got there by human introduction rather than by natural dispersal. Another example is saltmarsh cordgrass (Spartina alterniflora), a wetland plant that is native to eastern North American estuaries. Saltmarsh cordgrass was introduced to western North American shoreline habitats, where it did not occur previously. It has established and become a serious invasive species, displacing native species and adversely impacting wetland communities.

European settlers brought hundreds of plants to North America from their homelands for use as food and medicine, and for ornamental, sentimental, and other purposes. Introductions of exotic plants continue today and are greatly increasing due to a large and ever-expanding human population, increased international travel and trade, and other factors.

Once an Exotic, Always an Exotic! An estimated 3,500 species of exotic plants have escaped cultivation in the U.S., are able to reproduce in the wild, and have become established, or “naturalized.” These plants, how ever much a part of our current landscapes and ecosystems, are nonetheless exotic, since they were moved here by people. For centuries, horticulturists have imported and disseminated interesting new exotic plants. Unfortunately, many of these have become invasive pests that are having serious impacts to native species and ecosystems.

What Makes an Exotic Species Invasive? (When is a Guest a Pest?) Many non-native species exist in apparent harmony in environments where they were introduced. For example, a relatively small number of exotic plants (e.g., corn, wheat, rice, oats) form the basis of our agricultural industry and pose little to no known threat to our natural ecosystems. The most important aspect of an alien plant is how it responds to a new environment. An invasive species is one that displays rapid growth and spread, establishes over large areas, and persists. Invasiveness is characterized by robust vegetative growth, high reproductive rate, abundant seed production, high seed germination rate, and longevity. Some native plants exhibit invasive tendencies in certain situations.

How Many Plants are Invasive? According to the Plant Conservation Alliance’s Alien Plant Working Group, about 1,100 plant species have been reported as being invasive in natural areas in the United States (see link below). This number represents an astonishing one-third or so of the exotic plant species established and selfreproducing in the wild. Some invasive species were planted intentionally for erosion control, livestock grazing, wildlife habitat enhancement, and ornamental purposes. Others have escaped from arboretums, botanical gardens, and our own backyards. Free from the complex array of natural controls present in their native lands, including herbivores, parasites, and diseases, exotic plants may experience rapid and unrestricted growth in novel environments.

How Bad Are Invasive Species? Invasive species impact native plants, animals, and natural ecosystems by:

• Reducing biodiversity
• Altering hydrologic conditions
• Altering soil characteristics
• Altering fire intensity and frequency
• Interfering with natural succession
• Competing for pollinators
• Poisoning or repelling native insects
• Displacing rare plant species
• Increasing predation on nesting birds
• Serving as reservoirs of plant pathogens
• Replacing complex communities with single species monocultures
• Diluting the genetic composition of native species through hybridization

For additional information, please go to:

• Alien Plant Working Group “Weeds Gone Wild”
• Aquatic Nuisance Species Task Force
• Ecological Society of America
• Lady Bird Johnson Wildflower Center
• Mid-Atlantic Exotic Pest Plant Council
• National Audubon Society
• National Invasive Species Council
• National Park Service EPMT
• TNC Wildland Invasive Species Team
• US Geological Survey

Curly-leaf pondweed has been identified in over 500 water bodies in Minnesota. This non-native aquatic plant is often characterized as an invasive nuisance species and during the past few years many shoreland property owners have experienced increasing problems caused by its growth and spread. Requests for information and assistance with managing curly-leaf pondweed infestations have increased over the past two years. In response, the University of Minnesota Extension Service Shoreland Education Program recently offered three workshops to help property owners, local units of government, and lake association leaders better understand how to manage this nasty invader.

Workshops in Big Lake, Nisswa, and Richfield attracted nearly 150 participants who learned about the value of preserving native aquatic plants, the life cycle and characteristics of curly-leaf pondweed, various management methods (cutting, harvesting, chemical and physical options), recent research, and the permitting process for curly-leaf pondweed control. Speakers included representatives from the University of Minnesota Extension Service, Minnesota Sea Grant, Minnesota DNR, local governments, Minnesota Lakes Association, and private consultants and lake management professionals. Lake association leaders also shared their experiences in managing curly-leaf pondweed. The take-home messages for attendees: Preventing the introduction of curly-leaf pondweed into a water body is the only real “control.” There is, to date, no “silver bullet” method of eradicating curly-leaf pondweed once it has invaded a water body. Several factors need to be considered (with the help of natural resource professionals) before selecting an appropriate management method for a lake. Management of curly-leaf pondweed is costly, ongoing, requires a DNR permit, and may alter the ecology of the lake.

These workshops were co-sponsored by the Water Resources Center, Sea Grant Program, Minnesota Extension Service, Minnesota Lakes Association, and the Initiative Foundation.

Included in this issue of From Shore to Shore is a curly-leaf pondweed identification handout for you to use, make copies, and share.

This is the first in a series of articles about “exotic” plants – that is, plants that evolved over the past thousands (perhaps, millions) of years outside of a given geographical or ecological region. Plants considered exotic in Minnesota may include those originating in other parts of the US, Europe, Asia, or other countries. Exotic plants may be intentionally brought to Minnesota by the horticulture, aquarium, or other industries. Or they may have arrived here unintentionally as “hitchhikers.” Regardless of how they were transported to Minnesota, exotic plants leave behind insects and diseases that naturally controlled their population. Unchecked by natural controls in their new environment, these plants may become invasive – or not. In reality, most exotic plants do not become invasive (e.g., tulips, marigolds), but those that do share one or more of the following characteristics:

1. tolerance to a wide range of environmental conditions
2. reproduction early, often, in large numbers, and multiple ways
3. rapid growth
4. resistance to control efforts.

Invasions of exotic plants can be disastrous – displacing native plants, which are important sources of food and shelter for wildlife and fisheries. Invasive aquatic plants can change water chemistry and flow, impede navigation, and hinder recreation. Unfortunately, once they enter into an ecosystem it is often impossible to eradicate them.

Water Hyacinth and Yellow Iris.

Invasive exotic plants are recognized and regulated at the federal, state, and county levels - making it confusing for residents and nurseries to know just what plants they may grow, where they may be grown, and where they may be distributed. Plants on the Federal Noxious Weed List (e.g., kudzu) may not legally be sold, purchased, exchanged, or received into or through the US. Within Minnesota, the Department of Natural Resources and Department of Agriculture are responsible for regulating aquatic and terrestrial plants, respectively.

Aquatic plants on the Minnesota Prohibited Exotic Species List (e.g., purple loosestrife, Eurasian water milfoil) may not be possessed, imported, purchased, sold, propagated, transported or introduced within our state boundaries. In addition, plants that pose a moderate threat to natural waters and wetlands in our state are on the list of Minnesota Regulated Exotic Species. These regulated plants (e.g., yellow iris and water hyacinth) are legal to buy and possess, but it is illegal to place them in public waters or ponds that connect to public waters. Minnesota Department of Agriculture regulates the sales, importation, transportation, and/or occurrence noxious (exotic and native) terrestrial plants and seeds. They have several categories of state plant restrictions: Prohibited Noxious Weed, Prohibited Weed Seed, Restricted Noxious Weed, Restricted Weed Seed; as well as a County Noxious Weed category.

Whether transported unintentionally by wind, animals, water, vehicles or humans or are sold through catalog and Internet sales, these species are finding their way into and around our state. Future articles will discuss these plants in more detail – how they are spread, how to identify them, what you can do to minimize the risk of introduction and impact of these plants on our natural environment, and who to contact for further information.

Mary Blickenderfer, Shoreland Vegetation and Landscape Educator

You can spot us a mile away, scissors in our hands and pockets and packs bulging with bags of freshly collected native seed – the “bag people” of the native plant world! Once all the seed in those paper bags has dried on the porch or in the attic and/or the pulpy seed begins to ferment in plastic bags on your kitchen counter (see Minnesota Native Plants – Part 3 in July 2003 issue of this newsletter for collection instructions), you may be wondering “What do I do now?” The following instructions will help guide you through native seed cleaning and storage.

Cleaning seed

Dry seed: Remove seed from the seed head (shake heads in a bag, tap in a bowl, tease by hand, etc. – whatever works for the type of seed head you have). Sift with food strainers or a window screen (different mesh sizes can be used if available) and winnow (outside!) as necessary to remove the large chaff.

Wet seed: Clean when fruit is very ripe or fermenting. For stony seeded fruit, buzz briefly in a blender to separate the pulp from seed. If seed can be damaged by blender blades: wrap blades with duct tape, squeeze the fruit by hand while in the plastic bag, or work the fruit in a rigid container using a potato masher to separate the pulp from the seed. Rinse and decant liquid to remove the floating pulp and non-living seed from the viable seed that has settled to the bottom of the container. Repeat as necessary until decanted water is clean.

Storing seed

Dry seed: Place cleaned seed in labeled paper bags or envelopes. Store all labeled packages in a critter-proof container. A metal container with tight fitting lid is recommended. If insects are present, place pest strips in the container. Place container and contents in an unheated place (e.g., garage). Note: most dry seed, except seed of several sedge species, will retain viability for several years if kept dry, cool, and bug-free.

Wet seed and Wetland plant seed*: “Stratify” seed by planting it directly in flats containing moist growing medium. Place the entire flat in a plastic bag, label the bag, including the date stratification is initiated, and seal. Place in a location that will experience cold to freezing temperatures for a 6-8 week stratification period. A root cellar or unheated garage will work well for the flats, if critter-free. Check the flats during the stratification period: protect from critters and water, as necessary. If the seeds begin to sprout, remove them from plastic bags, place in a warm sunny location, and continue to care for the plants as necessary.

* Most dry seeds of wetland plants require a stratification to break dormancy (e.g., sedges, blueflag iris, boneset, Joe-pye-weed, swamp milkweed, blue vervain, etc.). Most other dry seeds will germinate more uniformly if stratified, but stratification is not required to break dormancy.

Other Notes:

As a general rule: store seeds under the conditions they would experience naturally if left unpicked. “Parachute-seeded” species (e.g., milkweed, asters, goldenrods, etc.) harvested just before they “fuzz out” are much easier to clean - if done immediately while the “fuzz” is still moist. A few species require “double stratification” (i.e. coldwarm- cold stratification). The first cold treatment is needed for root emergence. The second cold treatment is needed for leaf (cotyledon) emergence. Minnesota species that require this type of stratification include trilliums, highbush-cranberry, wood lily, and Turk’s cap lily.

Eleanor Burkett, Regional Extension Educator

In the summer of 2003, the University of Minnesota Extension Service Shoreland Education Program held three Aquatic Plant Identification workshops across the state. Locations included Rush City, Clinton, and Crosslake. The sessions filled to capacity with aquatic plant enthusiasts and firsttimers. The workshops included a segment on aquatic plants and how to use the plant identification manual, which was included with the workshop. At this session, participants were able try their luck on plant identification using dry herbarium plant specimens before the second session which was the real thing - to the lakes to collect aquatic plants and return ashore to key the plants for identification and learn how to properly label, mount and press plant specimens.

While future aquatic plant identification workshops will be offered, additional workshops are being planned for wetland and upland plant identification. Watch for information on all upcoming Shoreland Education Programs for 2004 in From Shore to Shore.