Wetland Plants
Note: These three sources are Planter's favorite sources for plant names and growing requirements for wet area plantings. Much of our lower field of evergreens is flooded in the spring. The area attracts deer, beaver and assorted birds, and wood frogs (or mole salamanders?) lay their eggs in the vernal pool.
1. Michigan State University Extension , Home Horticulture - 03900054 , 01/01/96
Wet areas in the landscape are usually problem areas. While
there are several solutions to wet ground, each solution
involves its own problems and a good deal of work. The
area could be filled, however this creates yet another
problem area in the landscape. Another option is to drain
the area and plant trees or shrubs. The creation of a water
garden is another solution; ideas for this may be gleaned
from a study of local natural bogs or wet areas and the
observation of plant associations and site differences.
When growing a water garden, it is important to place the
plants at sites where they will achieve optimal growth.
Trees and larger shrubs growing in mineral soils should be
placed along the banks or upon islands within the moist
area. Herbaceous species and smaller shrubs grow best in an
organic mat or soil. Proper soil reaction (PH), nutrient
and light requirements should be understood and observed.
The amount, depth and movement of the wet area is also
important.
Air drainage is directly related to plant hardiness. Wet
spots are low and are sinks for cold air, thus perennial
plants known to be intolerable of cold weather should not be
planted in these areas. Wild plants taken from the same
habitats will already have adapted to these conditions and
are better choices.
The following list recommends trees and shrubs for planting on wet sites: Trees: Acer rubrum Red maple A. saccharinum Silver maple Ainus spp. Alder Amelanchier spp. Serviceberry Betula nigra River birch B. papyrifera Paper birch Celtis laevigata Sugar hackberry Larix laricina Tamarack Liquidambar styraciflua Sweet gum Nyssa sylvatica Sour gum (tupelo) Picea glauca White spruce Platanus acerifolia London plane tree P. occidentalis Sycamore Populus spp. Poplar (aspen) Quercus bicolor Swamp white oak Q. Macrocarpa Bur oak Q. palustris Pin oak Salix spp. Willow Taxodium distichum Bald cypress Thuja occidentalis American arvorvitae Viburnum prunifolium Black haw
Shrubs:
Alnus incana Hoary alder Aronia arbutifolia Chokecherry Calycanthus floridus Sweetshrub Cephalanthus Button-bush occidentalis Chionanthus virginicus Fringetree Clethra alnifolia Summersweet Cornus alba 'Siberica' Siberian dogwood C. racemosa Gray dogwood C. stolonifera Redosier dogwood Crataefus crus-galli Hawthorn (cockspur) Gaylussacia spp. Huckleberry Ilex glabra Inkberry L. verticillata Winterberry Lindera benzoin Spicebush Magnolia virginiana Sweetbay magnolia Potentilla fruticosa Shrubby cinquefoil Rhamnus frangula Alder buckthorn Salix spp. Willow Sambucus canadensis American elderberry Spiraea alba Steeplebush Symphoricarpus spp. Coralberry Vaccinium spp. Blueberry Viburnum cassinoides Witherod V. dentatum Arrowwood V. lentago Nannyberry V. trilobum Cranberry viburnum
The following list recommends herbaceous species best suited
for wet sites:
Anemonella spp. Rue anemone
Arundo donax Giant reed
Asclepias incarnata Swamp milkweed
Thelypteris palustris March fern
Aster spp. Aster
Astilbe spp. Astilbe
Caltha palustris Marsh marigold
Campanula aparinoides Marsh bluebell
Carex spp. Sedge
Gentianopsis crinita Fringed gentian
Hibiscus moscheutos Rose mallow
Hydrocotyle spp. Water pennywort
Hypericum spp. St. Johns-wort
Impatiens biflora Touch-me-Not
Iris spp. Iris
Liatris spicata Blazing-star
Lilium canadensis Canada lily
L. superbum Turkscap lily
Lobelia cardinalis Cardinal flower
Mentha pulegium Pennyroyal
Myosotis scorpioides Forget-me-Not
Nuphar spp. Cow lily
Onoclea sensibilis Sensitive fern
Osmunda cinnamomea Cinnamon fern
O. regalis Royal fern
Pontederia cordata Pickerel weed
Primula japonica Japanese primrose
Ranunculus spp. Buttercup
Sagittaria latifolia Arrowhead
Saururus cernuus Swamp lily
Scirpus spp. Bulrush
Thalictrum spp. Meadow-rue
Tofieldia glutinosa False asphodel
Trollius spp. Globeflower
Typha latifolia Cat-tail
Vericona spp. Ironweed
Viola app. Violet
Zigadenus glaucus White camass
SOURCE: Working with Wet Areas in landscaping. by Harold Davidson,Department of Horticulture
Michigan State Univ. Extension Service Index
2. Source: U.S. Dept. of Agriculture
Wetlands filter excess pesticides and nutrients. Many plants and animals find a home in wetlands.
In your backyard
A mini-wetland in your yard can provide many of the same benefits that natural wetlands offer. A mini-wetland can replace the important natural functions of wetlands that may have been lost when your community was developed.
A wetland in your backyard will temporarily store, filter, and clean runoff water from your roof and lawn. It will provide habitat for many interesting creatures--from butterflies and bees to salamanders, toads, frogs, and birds.
Most wetland plants do not require standing water to grow successfully, and will survive even in an area that appears dry during most of the growing season.
If you have a naturally occurring wet spot in your yard, or a low swale or drainageway
with heavy clay soils, you easily can turn it into a wetland paradise. Even if you do not
have a naturally wet spot, you can establish an area in your yard to grow many of the
beautiful plants associated with wetlands.
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What is a wetland?
A wetland is simply any area where water covers the soil or keeps it saturated for at least two or three weeks during the growing season. You will usually find them anywhere water accumulates at a rate faster than it drains away. Some are inundated year-round while others only hold water for brief periods in the spring. Most wetlands are covered with water for less than a month during the summer. Wetlands dominated by grasses, cattails, and similar herbaceous vegetation are referred to as marshes, while wooded wetlands, dominated by shrubs and trees, are called swamps.
The saturation of the soil limits the types of plants you can grow to those with "wet feet." How long the soil is saturated determines which wetland plants will grow best. There are many small wetland plants that grow quickly when the soil is wet in the spring and disappear when the soil dries up. Species like cattails, bulrushes, jewelweed, and the attractive cardinal flower do well where there are alternating wet and dry periods. These plants will survive persistent flooding as long as most of the leaves are out of the water. Water lilies and pond weeds grow well in permanently flooded ponds.
In your backyard, toads and tree frogs (spring peepers) will lay eggs and the pollywogs will mature where water only lasts 3 or 4 weeks; other frogs need longer periods. Where you have permanent water, the bullfrog pollywogs and small fish eliminate reproduction of most other frogs, toads, and salamanders. Mosquitoes will not survive in wetlands that dry out in less than a week after a summer rain or in wetlands connected to a deeper pond that supports small fish and large aquatic insects that feast on them.
Where to put a wetland
A natural depression or ditch that tends to stay wet is an ideal place to develop a wetland. Other areas with heavy clay soils that drain slowly may also be suitable. Better drained sites may require use of a plastic or other type of liner. Of course, if you are building a backyard pond, as discussed in another tip sheet in this series, a shallow area of saturated soil can be incorporated in the design. When selecting a site, consider:
Is the site away from your foundation, out buildings, existing landscaping that you
want to maintain, or neighboring properties that might be damaged by excessive moisture?
Would there be a safety concern for neighborhood children?
How will the site be integrated into your plan for maintenance?
If you need supplemental water, is it readily available or can you use roof drainage?
If there is an existing wetland, check state and local wetland regulations before altering
it.
Unless you completely own a ditch, check with local authorities before making any
alterations. Be sure you won't cause adjacent properties to flood.
Building a wetland
Since wetlands refer to a variety of conditions, there is a lot of potential for including wetland plants in your yard. You may want a wetland that only stays wet for a short period after heavy rains or one that stays wet most of the time. It depends on the site and your desires. Establishing a wetland in your yard may be as simple as planting wetland plants in an existing wet area, or it may require the same effort needed to install a backyard pond.
Building a wetland in an existing wet area or drainageway
In some instances, all you need to do is stop mowing during dry periods. Too often homeowners go to great lengths to establish plants that are not adapted to the site or to modify the site, when it would be more effective to use plants suited to the conditions. Numerous landscape plants are well adapted to wet conditions and will provide beauty as well as wildlife habitat. Be sure to check the growth and rooting characteristics of trees you want to plant. Many wet soil tolerant trees have shallow root systems or brittle branches and must be planted a safe distance from buildings.
Partially blocking a drainageway or small ditch to create your wetland by trapping storm water needs more planning. Where a low berm less than a foot high will create a small wetland, planning is not complicated if:
the drainage area above the berm is small, generally less than an acre;
there is adequate area for flood flows to go around and over the berm; and
the soil contains a high percentage of clay.
For sites requiring a higher berm, and those with a larger watershed, you need engineering
advice. For sites with sandy soil or a lot of rocks, you also may need to install a
plastic liner (described in the next section) under all or the lower portion of your
wetland.
To construct the wetland with a small berm to hold back water for a few days or weeks:
1. Put a stake in the center of the lowest portion of the drainageway where you want the berm.
2. Using a level on a large board or string, place a stake where a level line reaches the ground on either side.
3. Using the same type of level, mark how far back water will be impounded at the top of the berm.
4. Remove any existing sod from an area about 4 feet wide along the line of the berm and over about half the area that will be flooded.
5. Dig a trench about 1 foot deep along the center line of the berm and fill it with slightly damp heavy soil, packed down firmly.
6. Build your berm about 4 feet wide at the bottom and 1 foot at the top. The center should be 4 to 6 inches higher than the ends to allow for settling and to force water flowing over it around the ends, reducing the likelihood of erosion.
7. Cover the compacted berm with purchased grass sod or the sod you originally removed from the area.
8. Plant wetland adapted plants in bands from the deepest areas to an area about six
inches above the expected high water level, selected according to the degree of soil
saturation they require.
Establishing plants
The plants you select for your wetland will depend on:
length of time the soil will be saturated or covered with water,
depth of the water,
amount of sunlight on the site,
climate,
soil pH, and
size of the wetland.
Select plants that are hardy for your area and provide the desired wildlife habitat and
aesthetics. The species of plants most common in other wetlands in your area with similar
flooding cycles will be easiest to grow and need the least maintenance.
Choosing and establishing plants for ponds
To make part of your backyard like natural wetlands, use a mix of diverse plants. Most trees, shrubs, ferns, and many other plants grow best in soils that are only saturated early in the growing season and after heavy rains. Others, like the true bog plants, need almost continually saturated soil. Plants like water lilies need to be continually flooded. Once established, plants like cattails will thrive in water a couple feet deep, but also in areas that are wet for only short periods. However, most have a narrower tolerance range that may vary depending on where you live. Always check with your local nursery or other expert before making final decisions on what varieties to plant. Plants should always be purchased from a reliable source.
Native trees tolerant of wet soils:
Red and silver maple (Acer rubrum, A. saccarinum)
River birch (Betula nigra)
Catalpa spp.
Ash (Fraxinus spp.)
Cottonwood (Populus deltoides)
Swamp white oak (Quercus bicolor)
Sycamores (Platanus spp.)
Native shrubs tolerant of wet soils:
Red osier dogwood (Cornus sericea)
Leatherwood (Dirca palustris)
Winterberry (Ilex verticillata)
Inkberry (Ilex glabra)
Pussy willow (Salix discolor)
Shrubby cinquefoil (Potentilla fruticosa)
Native herbaceous and flowering plants for sunny moist or boggy conditions:
Cattails (Typhus spp.)
Joe-Pye weed (Eupatorium maculatum)
Great blue lobelia (Lobelia siphilitica)
Ironweed (Vernonia noveboracensis)
Blue flag iris (Iris versicolor)
Boneset (Eupatorium perfoliatum)
Cardinal flower (Lobelia cardinalis)
Goldenrods (Solidago spp.)
Marsh marigold (Caltha palustris)
Swamp milkweed (Asclepias incarnata)
Gentian spp.
Native herbaceous and flowering plants for shady moist or boggy conditions:
Bee balm (Monarda didyma)
Arrowhead (Sagittaris latifolia)
False hellebore (Veratrum viride)
Turtlehead (Chelone spp.)
Skunk cabbage (Symplocarpus foetidus)
Royal fern (Osmunda regalis)
Netted chain fern (Woodwardia areolata)
Jack-in-the-Pulpit (Arisaema triphyllum)
Cinnamon fern (Osmunda cinnamonmea)
Shield ferns (Dropteris spp.)
Lady ferns (Athyrium spp.)
True bog plants requiring low pH and sun:
Sundews (Drosera spp.)
Butterworts (Pinguicula spp.)
Pitcher plants (Sarracenia spp.)
Numerous other native wetland species are available in most areas. There are also many
species that have been naturalized in North America and are often considered native
plants. Unfortunately, some of these species are more competitive and have become
invasive, crowding out the native species that provide habitat for indigenous wildlife.
USDA - NCRS Wetlands Program: http://www.wl.fb-net.org/
3. Source: Michigan State Univ. Extension Index
GROWING WETLAND PLANTS
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Wetland plants should receive full sun or at least 1/2 day
full sun for marsh/wet meadow plants. Light shade for
swamp/wet woods plants is recommended. Soil requirements
for wetland plants include at least 2 inches of humus needed
on the surface of the soil. Wet soils can be compacted if
worked while wet, to allow rain and soil organisms to work
the humus into the soil. The soil should be kept very
moist; it should be totally saturated in early spring and
never allowed to dry out for more than 3 to 4 days the rest
of the year. However, the plant tops shouldn't be immersed
in water, however. The pH level required is between 6.5
and 7.0.
Wetland plants also have specific requirements for optimal
growth:
Blue lobelia (Lobelia siphilitica), requires:
Light: Sun to medium shade
Soil/Moisture: Wet woods, swamps
PH: Average
Height: 1-3'
Flowering Time: August-September
Propagation: Stratification not needed; stem cuttings in
summer; division in spring.
Blue vervain (Verbena hastata), requires:
Light: Sun
Soil/Moisture: Wet meadows
PH: Moderately acid
Height: 1-3'
Flowering Time: August-September
Propagation: Stratification not needed.
Cardinal flower (Lobelia cardinalis), requires:
Light: Sun to medium shade
Soil/Moisture: Swamps, wet woods
PH: Moderately acid
Height: 2-4'
Flowering Time: July-August
Stratification not needed; stem cuttings in summer; division
in spring.
Iris, blue (Iris spp.), requires:
Light: Sun to light shade
Soil/Moisture: Marshes, wet meadows
PH: Average
Height: 1-3'
Flowering Time: May-July
Propagation: Stratification not needed; division in spring.
Rhizome is poisonous
Marsh marigold (Caltha palustris) requires:
Light: Sun to medium shade
PH: Not specific
Height: 8-24"
Flowering Time: April-May
Propagation: Seeds planted immediately in wet soil; division
in spring.
Mints (Mentha spp.), require:
Light: Sun
Soil/Moisture: Marshes, wet meadows
PH: Average
Height: 1-3'
Flowering Time: June-September
Propagation: Stratification not needed; division in spring.
Should be controlled; it may spread,
Monkey flower (Mimulus ringens) requires:
Light: Sun
Soil/Moisture: Marshes, wet meadows
Height: 1-3'
Flowering Time: June-September
Propagation: Stratification not needed;
division in spring; stem cuttings in summer.
Swamp milkweed (Asclepias incarnata) requires:
Light: Sun
Soil/Moisture: Marshes
PH: Average
Height: 2-4'
Flowering Time: June-August
Propagation: Stratification not needed; division in spring.
All parts poisonous.
Turtlehead (Chelone glabra), requires:
Light: Light to medium shade
Soil/Moisture: Swamps, wet woods
PH: Average
Height: 1-3'
Flowering Time: July-September
Propagation: Seeds stratified; division in spring; stem
cuttings in summer.
Michigan State Univ. Extension