Megunticook Watershed Association

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Buffering for Water Quality

Spring is here, at least astronomically speaking and that means that gardening season is coming soon. It is an excellent time to plan to make your Megunticook property more water-quality friendly and less Canada goose-friendly. By installing a buffer zone full of plants along the water’s edge of your property, you can accomplish both and add an extra dimension of interest and habitat at the same time.

The lake water quality suffers when run-off from parking areas, driveways, or slopes planted with shallow-rooted grass permits pollutants such as oil and other leakages from parked cars, lawn amendments, and even naturally occurring phosphorus, a ubiquitous element found in soils, to have easy access to the lake. The effect is worse if there is even a slight slope or grade down to the lake. If geese are an extra added factor and their droppings are not picked up and removed from the scene, they also can make their way into the water resulting in possible bacterial contamination in the immediate area. Phosphorus is particularly bad because this is the factor responsible for algae blooms that rob the lake of oxygen, and can eventually accumulate to such a degree that algae blooms become an unfortunate annual event. Not only is it unsightly but fish and populations of other water animals suffer as a result. No lakeside lawn should be fertilized with any phosphorus-containing fertilizer to prevent this extraneous source from washing into the lake. (There are phosphorus-free fertilizers available. Make sure you read the label. A capital letter P is the symbol for phosphorus, K is for the other element in fertilizer starting with P, potassium.) But the biggest source of phosphorus can be just from the soil itself.

A planted buffer can be of any size, but bigger is always better! From the lakeside, geese will not be able to see anything that they like to eat so they will stay off, even if you have grass beyond the buffer zone. A mixture of plants with different root length and structure will provide better soil and water holding functions and will be better for topside viewing too. Remember that grass roots are only a very few inches long whereas other plants send roots down much deeper into the soil and are therefore much better candidates for erosion control and water filtration as well. If you have a path down to the water, plants on either side will eventually send roots under the path to stabilize the soil underneath. Just remember to try to plant so that any water that could run down the path is diverted from going directly into the lake. Then the plants will have a chance to absorb the flow. Even a well-placed rock or decorative element can be useful.

As with any garden, planning is a good place to start a project and usually results in a more successful outcome. You might consider the project as an opportunity to re-landscape the area that will also add value for wildlife as well as for aesthetics. It might be time to minimize the lawn – a very effective lake-saving (and energy saving) strategy. Overall, it could enhance the value of the property itself and you would also get satisfaction out of knowing that your efforts are helping the lake stay in good shape.

There are many plants that could be good choices for a lakeside planting. Your choices will depend on several factors such as the amount of sun or shade in the area, whether the edge slopes to the water and consequently the plants might be underwater early in the spring, how tall or short the plants need be for privacy or open vistas, and seasons of interest. Native plants are a great choice to include for they are preadapted to the Maine environment and look right at home from the beginning. Maintenance issues might be a concern for some people. Browsing deer in the wintertime also influence choices. Remember that newly planted areas must be watered regularly as the get established but a thick layer of mulch will hold moisture around the plants to minimize this task.

Here are some suggestions to start with but there are lots of resources available that also will have ideas. Included are plants that are likely to be found in local nurseries of good size and ready to plant, but if you plan ahead, even smaller plants ordered from mail-order sources can be excellent choices and get acclimated sometimes even easier than larger specimens. These plants listed below are less likely to be munched on by deer than other options but truly there are many other fine plants that could be used.

Abbreviations: F = full sun
P = part sun, part shade
S = shade

Small trees:

Mountain maple, Acer spicatum, (F,P)
American hornbeam,Carpinus caroliniana spp.virginiana, (F) – can tolerate flooding
Black gum, Nyssa sylvatica, (F,P) – a bit taller growing but lovely fall color for extended-season camps
American mountain ash, Sorbus Americana, (F) – known as source of food for wildlife

Shrubs:

Bog rosemary, Andromeda polifolia var glaucophylla, (F,P) – needs moist acid soil, only 1 foot high!
Summersweet, Clethra alnifolia, (F,P) – flowers in mid-late summer, excellent for sun or part shade
Sweetfern, Comptonia peregrina, (F,P) – excellent low-grower that fixes nitrogen, grow back from lake, prefers drier sites
Witchhazel, Hamamelis virginiana, (F,P,S) – flowers late in fall but nice native plant
Winterberry, Ilex verticillata, (F,P) – fruiting, needs female plants and at least one male plant, good for lake edge.
Sweetgale, Myrica gale, (F) – bushy plant with fragrant foliage, can tolerate flooding
High-bush blueberry, Vaccinium corymbosum, (F,P) – can tolerate wet location, acid soil best

Perennials, wildflowers:

Spikenard, Aralia racemosa, (P,S) – taller, white flowers
Turtlehead, Chelone glabra, (F,P) – white flowers late summer, wet-feet tolerant
Swamp milkweed, Asclepias incarnata, (F) – needs moisture, pink summer flowers
Bunchberry, Chamaepericlymenum canadensis, (P,S) – low-growing native dogwood relative, ground-cover
False sunflower, Heliopsis helianthoides,(F,P) – upslope, dense root system, summer flowers, tall plant, highly rated for erosion/water control
Blue flag iris, Iris versicolor,(F,P) – blue flowers, early summer, wet-feet tolerant
Cardinal flower, Lobelia cardinalis, (F,P) – stately red flowers, wet-feet tolerant, hummingbird favorite, grows wild along lakeshore
Blue vervain, Verbena hastata, (F,P) – tallish purple flowering perennial that adapts to wet locations
Asters, various species, (F,P) – later blooming, white and purple flowers depending on species, very important for beneficial insects
Goldenrods, (F,P) – excellent for wildlife, later blooming

Non-flowering perennials:

Tussock sedge, Carex stricta,(F) –very much a wetland plant, great for erosion and water control, utilized by lots of wildlife including wetland birds
Crested wood fern, Dryopteris cristata, (P,S)
Soft rush, Juncus effuses, (F) – wet feet and sandy or mucky soil preferred , will grow in water up to 4 inches but can be established in garden with regular watering
Cinnamon fern, Osmunda cinnamornea, (P,S)
Royal fern, Osmunda regalis, (F,P,S)
New York fern, Thelypteris noveboracensis,(P,S) – dappled sunlight

Photographs of many of these plants and more information about them can be found at this excellent website: www.illinoiswildflowers.info

Planting suggestions:

Needless to say, any disturbance of the existing soil is going to offer the possibility of runoff during planting and for the time it takes for the plants to get established. To minimize this potential, it would be better to plant the plants individually into the existing soil rather than to turn the bed over at one time or at all. Leave existing roots and rocks and plant around them, as counter-intuitive as that seems. Research (botany.wisc.edu/zedler/images/leaflet_15_jan_17.pdf) has shown that adding topsoil is not a good idea for it encourages top growth at the expense of root growth. Roots are the part of the plant that is essential for controlling runoff and is, in truth, the rationale for choosing these plants. With extra soil, the plants might look better to begin with, but as functioning entities in the environment, with less roots they will not do as well in their job of keeping unwanted substances out of the lake. In fact, nutrients could easily wash into the lake from any soil amendments used at planting time. This is one reason why native species are better choices since they are likely to grow more vigorously in less fertile soil than plants more traditionally used and developed for ornamental gardens. Save those choices for areas far back from the lake or on the inland side of any structure where more typical horticultural maintenance practices are safely used.

If there is a steep grade down to the lake, extra caution must be taken. Justin Nichols, horticulturist at Coastal Maine Botanical Gardens, suggests installing and planting through a bio-degradable erosion control matting and diverting water with stones and other added items such as log or wood pieces. A mulch of leaves or straw helps also to avoid washing out the new planting from rainfall. Hiring a professional landscaper who has had special training for erosion control would be a good idea for major planting projects.

References and for more information:

The Buffer Handbook Plant List, www.maine.gov/dep/land/watershed/buffplantlist.pdf
Vegetative Buffer Zones, www.sustland.umn.edu/design/water2.html
Shoreland Design, Resources For Additional Information On Vegetative Buffer Zones, www.sustland.umn.edu/design/water3.html
Contractors Certified in Erosion Control Practices: www.maine.gov/dep/land/training/ccec.html