Ron Struss, University of Minnesota Extension Educator

Have you heard this adage?: One pound of phosphorus can produce from 300 to 500 pounds of algae. You probably have. It is much quoted in articles and during presentations when the “greening” of lakes is discussed. It means a pound of the nutrient phosphorus entering a lake (or river) from wastewater or stormwater runoff can promote the growth of up to 500 pounds of “pea soup” algae.

Not only have I heard this adage, I have repeated it to others - which led me to ask, where did it come from, and is it TRUE?

Steve Heiskary, limnologist with the Minnesota Pollution Control Agency, put me on the trail of the “algae adage” origins by directing me to Limnology, a standard textbook by Robert G. Wetzel. While it is not known who first coined the adage, the rationale for it is laid out in a section titled Effects of Phosphorus Concentration on Lake Productivity (Second Edition, page 285). A main reference for the section is J.R. Vallentyne’s book The Algal Bowl – Lakes and Man (Ottawa Department of the Environment, 1974).

Core to the rationale is the “law of the minimum”, that is, the nutrient that is in the shortest supply in relation to a plant’s needs will control the growth of that plant. The “law of the minimum” can be illustrated using a baking example:

A pound cake takes a pound of flour, a pound of butter, a pound of sugar and four eggs. If you have ten pounds of flour, butter, and sugar, but only four eggs, you can only bake one pound cake. The eggs are the limiting factor to baking more.

The limiting factor for algae growth in most Minnesota lakes is the nutrient phosphorus. It is not limiting because algae need so much of it, but rather because it is usually in very short supply. The average ratio of the phosphorus needs of algae to what is available in water is 80,000 to 1.

According to J.R. Vallentyne, a 500 pound “batch” of wet algae requires:

• 1 pound phosphorus
• 7 pounds nitrogen
• 40 pounds carbon

Since there is usually more than adequate levels of nitrogen and carbon in lake and river water, for every pound of phosphorus added, another 500 pound batch of wet algae can be produced. Since 500 pounds is the theoretical maximum that can be produced, the range of 300 to 500 pounds is typically used when the adage is quoted. I did not find how the 300 pound lower limit was set – it is likely the best estimate of the specialist who first coined the adage. The 300 pound to 500 pound range is wet weight algae; in dry weight the range is 60 to 100 pounds.

All types of algae can experience periods of rapid growth known as “blooms”. In Minnesota lakes, however, blooms of blue green algae, also known as cyanobacteria, draw the most notice. They form surface scum, are smelly, and occasionally produce toxins harmful to drinking livestock and pets.

Blooms of blue green algae are a classic case of too much of a good thing. We owe lots to blue green algae for both past and present good. Similar to bacteria in structure, these simple organisms are credited for first using chlorophyll to make food from sunlight and for boosting oxygen in the Earth’s early atmosphere. In lakes today they form the base of the food web that feeds increasing larger and larger animals - including you if you were lucky enough to hook a lunker this season!

Mary Blickenderfer, Extension Educator

One good source of plant material for shoreland restoration projects is hand-collected seed from local native stands. Hand-collected seeds may be broadcast directly at a restoration site, or plants grown from the seed may be used. Plants produced from locally collected seed will be adapted to local site conditions. In addition, native seed collecting is a great way to increase one’s native plant repertoire and become familiar with the ecology of a plant – under what soil-sun-moisture conditions it grows, what other plants are naturally associated with it, whether it occurs in small patches (“accent plant”) or in large beds (“matrix plant”), when it blooms, its height, etc.

Before you collect

1. Know the plant species you’re collecting. Don’t collect aggressive species that may cause problems later. Also, make sure the species is not listed as “threatened” or “endangered” or on the state/federal list of “noxious weeds.”
2. Obtain permission to collect seed if not on your own private property.
3. Consider marking the plants while they are at a stage that they can be most easily identified. For flowers, this will be when they are in bloom. For grasses and sedges, this will be when they set seed. This will facilitate accurate identification and ease of locating them during collection later in the season.
4. Select only large populations of plants for collecting.
5. Monitor these plants as they mature, testing the seed for ripeness. To test seed, press a kernel between your thumbnail and finger. Seed kernels will go through several stages before they are ready to collect: first milky juice, “soft dough” (like soft bread dough), “hard dough” (like stiff cookie dough), and finally firm (hard to the touch). Seed is ready to harvest when firm.

Collecting seed

When collecting seed make sure you bring paper bags for the “dry” seed (e.g., grass, aster, bergamot) and/or plastic bags for the “wet” seed (e.g., Jack-in-the-pulpit, Solomon’s seal and other seed surrounded by pulp or seed that needs to remain moist to maintain viability), marking pen, scissors or pruners, and a pack to carry these items.

Collect seed according to the “1/3 Rule” (i.e. collect no more than 1/3 of the seeds from 1/3 of the seed heads of 1/3 of the plants in any given population). Cut, prune, or hand-strip seed heads, placing the seed in a bag. Be sure to label each bag with the following information: date, state (if collecting in more than one), county, specific location (lake, nearest city, etc.), plant name or identifying # (be sure the label includes the complete scientific name, even if you have to look it up and add it after returning home), collector, and other notes (about quality of seed, insect damage, unusual growing season or site information, etc. – as necessary).

After you collect seed

A general rule for flower species with seeds that reach maturity in early summer – June or July (e.g., trillium, bellwort, bloodroot, violets, marsh marigold, Canada anemone) is to plant the seeds immediately in soil and keep watered through the growing season. This will maintain their viability and fulfill the first stage of the requirements for breaking dormancy. Note that trillium, bellwort, bloodroot, and violet seed have a fatty appendage called an “eliasome.” Ants carry these seeds into their anthills where they eat only the high-nutrient eliasome and inadvertently plant the seeds.

For most grasses and seeds that reach maturity in late summer and fall, hang bags of “dry” seed in a warm, dry place to thoroughly dry, stirring seeds occasionally. Keep bags of “pulpy” seed at room temperature until you are ready to clean. If they start fermenting, refrigerate until ready to clean. Seed cleaning, storing, and growing techniques will be covered in upcoming issues of this newsletter. Beware - seed collecting can be addicting!

Reference:

Baskin, C. and J. Baskin. 1998. Seeds – Ecology, Biogeography, and Evolution of Dormancy and Germination. Academic Press: London. 666 pp.

Mary Blickenderfer, Shoreland Vegetation and Landscape Specialist

Some of the most common questions at shoreland revegetation workshops is “Where can I get native plants for my project?” and “What do they look like?” Many people are interested in buying plant materials from a nursery or supplier, while some are interested in collecting and/or propagating the plant materials themselves. Most types of native plant materials are similar to those found in a standard nursery. However, the pre-vegetated mats for aquatic plantings are relatively new. Below is a table that will help address these questions.

* Planting below the Ordinary High Water Level (i.e. in the aquatic and wet transition zones) is limited to MN native species and requires a DNR permit prior to planting.

** Always obtain permission from property owner before collecting any plant material. Written permission (permit) may be necessary and is always advised.

Whether plant material is purchased from nurseries or collected from friends’ gardens or a wild area, it should be done with some caution. Remember, we want to use plant material with genetic origin from 1) the same ecological region as the planting site (see Feb/Mar issue) or 2) Minnesota (a much easier working definition!). A list of nurseries and suppliers of MN native plant materials recently created by a Master Gardener is available on line (http://www.uslink.net/~wetdog/nativenurseries.html). Note that our working definition of “MN native plant” may not be the same one used by the nurseries on this list or your gardening friends.

If purchasing seed, you can choose either individual species or special mixes. Ask if it is “yellow tag” or “source identified” seed, and if so, what is the place of origin (Minnesota?). Is the native seed produced from “released” varieties that have been selected from a large region, covering several states? If so, avoid. Again, be extremely cautious of “meadow-in-a-can” or “native seed” packets sold at discount stores and garden centers. Check the label - many contain seed from distant regions of the country and should be avoided. Many MN native seed suppliers listed on the website given above offer similar seed mixes for our state. Note that most native seed is much smaller and lighter than most non-native grass and flower seed. Expect to purchase significantly less (by weight).

If purchasing plants ask about the source of seed or plant cuttings used for propagation (Minnesota?). If the plants appear to have been dug from the wild (i.e. several different species in the same pot, unusual soil, etc.), determine if they were salvaged from a demolition site or dug from an otherwise undisturbed natural population. Supporting the latter method may unnecessarily put native plant populations at risk and should be avoided.

If collecting seed from the wild or transplanting make sure you have permission from the owner to do so. Then make sure that the species is truly native. If collecting seed, mark the plant or site and monitor until ripe (covered in upcoming issue). Transplanting from the wild is recommended only when the site is scheduled for future demolition. In some areas, an effort is being made to coordinate transplanting from sites of aquatic plant removal to sites of aquatic plant revegetation – ask the DNR when applying for a permit to transplant aquatic vegetation.

Mary Blickenderfer, Regional Extension Educator

Orders for native flowers, grasses, trees and shrubs are pouring into my local Soil and Water Conservation District for their spring plant sale…local shoreland property owners want to know how to collect seed and grow plants for their shoreland revegetation projects… schoolteachers are calling with questions on how to create native plant gardens for outdoor classrooms…several local business are attending the Lakescaping for Nursery and Landscape workshops coordinated by the Minnesota DNR… These recent events are evidence of the overwhelming interest in landscaping with native plants – especially for shoreland revegetation projects and water features – and the urgent need for information on how to use native plants successfully in the landscape.

Starting with this issue, Plant Topics will answer questions on why and how to use native seed and plants from local sources in shoreland landscaping. In this issue we will discuss what is a “native plant, “ and when and why we should use them. Upcoming issues will discuss native seed and plant sources, collection techniques and issues, amazing adaptations of native seeds and plants, cleaning and storing seed, propagating native plants from seed and cuttings, special propagation techniques for aquatic plants, and how to use and manage native plants in the landscape. Readers are encouraged to contact me with their native plant questions for inclusion in upcoming issues (Mary: 218-327-4616).

First of all, what is a “native plant?”

Using the broadest definition, every plant is native to the world! However, some plants are only found in very unique, local climate or soil conditions. Our working definition will fall somewhere in between. Nearly every native plant nursery and native plant restoration practitioner has their own working definition of what is native, usually measured in miles from a plant source. Agencies tend to use political (often state) boundaries. However, recent research indicates that the ecological classification system that divides Minnesota into three regions (see map) provides the best working definition. That is, native plant materials should be collected, propagated, and planted within a single ecological region.

Why shouldn’t we use plants from outside our ecological region?

The reasons are many. First, non-native plants may have no local “checks and balances,” in the form of insects and diseases, to control their population and may aggressively out-compete the native vegetation (Need I remind you of our constant battle with purple loosestrife, Eurasian water milfoil, curly-leaf pondweed, European buckthorn and honeysuckles – to name just a few?). Even plant cultivars bred from sources native to the Midwest may exhibit similar aggressive behavior (“Blackwell” switchgrass is one to avoid.). As many know, non-native plants may not survive our harsh northern climate (How many dollars are wasted on water plants ordered from southern sources or “meadow-in-a-can” mixes from California sold in local department stores?). Alternatively, plants from outside an ecological region may survive within a region but not be able to reproduce under local climate or soil conditions. Finally, there is a growing body of research indicating that non-native plants provide inadequate habitat for the local wildlife, in many cases threatening their survival.

When are non-native plants appropriate in the landscape?

Non-native plants and cultivars provide welcome additions of color, texture, and form to a landscaper’s pallet. They can be used most effectively in plantings close to dwellings, offices, or other public areas where they can be readily viewed, enjoyed, and maintained. Use of non-natives in water features (man-made ponds or water gardens) or in close proximity to public waters is discouraged in an attempt to prevent another “purple loosestrife event.” It is important to note that planting non-natives in public waters (below the Ordinary High Water Level) is prohibited for the same reason.