Native Plantings Revive Wet Meadow Ecosystems

Published on April 26, 2021

By not mowing to the pond’s edge (top), we were able to increase plant diversity.

Water in the landscape creates many opportunities for habitat creation and enhancement. After all, the enjoyment that open-water habitats, backyard ponds and water features provide for amphibians, fish, birds and humans alike is well known and at the core of mainstream gardening.

A large and often overlooked opportunity can be found in gardening the wet, seasonally “unmowable” areas of the landscape, including wetlands and fallow farmland. Over the last decade, pollinators and green stormwater management have been building a growing interest in going native among homeowners, businesses and corporate campuses. Wet areas can tap into the power of native plant diversity and create a functioning wet meadow or wetland habitat by properly planting and seeding according to the season. At best, they can transform an overlooked landscape into a restored habitat with renewed ecological function.

The Henrys live on five acres in southeastern Pennsylvania (growing Zone 6a) that was historically farmed and grazed until the late 1960s. The soil on the property consists of fine silt loam with the water table 6 to 18 inches below the surface and a fragipan layer at 18 to 22 inches. None of the soils is classified as hydric; however, there is a perched water table that leads to seasonal ponding and the presence of obligate vegetation.

Since the legacy seed bank was still somewhat intact, a wet meadow matrix of sedges, rushes and other wet-loving forbs have emerged, along with other undesirable non-native annual, perennial and woody plant species.

The Henrys are native plant enthusiasts, so they were pleased to know that there was already a preexisting population of wet meadow species. However, the meadow had deteriorated. The family wished to improve the wet meadow diversity but wasn’t sure where to start.

Wet Meadow or Wetland?

Wetlands are defined by the U.S. EPA as areas where water covers the soil or is present either at or near the surface of the soil all year, or for varying periods of time during the year, including during the growing season. Water saturation, or hydrology, largely determines how the soil develops and the types of plant and animal communities living in and on the soil. Wetlands may support both aquatic and terrestrial species. The prolonged presence of water creates conditions that favor the growth of specially adapted plants (hydrophytes or obligate vegetation) and promote the development of characteristic wetland (hydric) soils.

Mountain mints
Mountain mints are deer resistant and attract more than 63 beneficial insects.

A wet meadow is predominantly an open habitat with seasonally saturated soil dominated by herbaceous plants, typically hydrophytes. If there is hydric soil present, it is a wetland. If not, it is just a wet meadow. Regardless of official designation, both habitats provide essential ecosystem services for pollinators, wildlife and water quality. The Henrys had a wet meadow in need of enhancement.

Blending Ecosystems

The protocol for establishing most wetland meadows calls for the removal of existing vegetation by smothering, tilling or herbicide, then establishing a blend of seeds. The Henrys had misgivings about scraping the existing ecosystem, so a unique strategy was devised — one that had distinct challenges, but a main advantage of preserving the diversity of existing vegetation on-site.

The first step was to use landscape plugs to introduce vegetation that was missing from their meadow environment. In this case, the conspicuous absence was two foundational groups of plants: perennial forbs and warm season grasses. The meadow had none of the beautiful flowering plants that are the stars of wet meadows — no iron weed (Vernonia noveboracensis), Joe-Pye weed (Eutrochium fistulosum) or cardinal flower (Lobelia cardinalis). Absent, too, were the tall, late-summer grasses like Little bluestem (Schizachyrium scoparium) and Switchgrass (Panicum virgatum) that take up valuable real estate to keep annual weeds at bay.

Iris versicolor is always a good choice for its late-May blooms.

This situation was likely a result of browse pressure from whitetail deer. A secondary impact from the deer seemed to be a proliferation of annual weed species, including Japanese stilt grass (Microstegium vimineum) and joint head basketgrass (Arthraxon hispidus) that had pioneered disturbed areas as tall perennial forbs had been browsed to near extinction. In turn, the fast-spreading annual joint grasses had discouraged warm season grasses from regaining a foothold.

The intention was to establish thick warm and cool season cover to help compete with the annual weed pressure and begin to form the basis of an attractive, diverse wet meadow. The suggested plant list included wet-loving, strongly rhizomatous flowering perennials like wrinkle leaf golden rod (Solidago rugosa), purple stem aster (Symphyotrichium puniceum) and mountain mint (Pycnanthemum tenuifolium) to hold ground and provide important nectar sources for native pollinators. On the drier parts of the meadow, warm season grasses like switchgrass and little bluestem were introduced. Also included were cool season sedges and grasses like tufted hairgrass (Deschampsia cespitosa), soft rush (Juncus effusus) and water sedge (Carex aquatilis).

Filling the Gaps

Initially, the Henrys had looked to gallon-sized plant material and the immediate gratification of mature plants, but price and availability were a barrier. After much convincing, and given the presence of hydrology and the diversity of species they wished to include, landscape plugs were a sure bet. Plugs are not only more cost effective, but they also minimize disturbance when planting and root faster to become more vigorous plants.

Swamp milkweed bee
Swamp milkweed is always a happy stop for passing pollinators and other beneficial insects.

Planting plugs alone was not enough; a management regime was essential. Initially, a prescribed burn was used to knock down existing thatch, which allowed for good establishment of the installed plugs. However, it consequently caused a flush of joint head basketgrass. This was followed by a seasonal high-mowing regiment the following spring, which allowed warm season plants an opening to get a head start on competing with annual weeds. In the fall, a wet meadow seed mix was broadcast throughout the meadow area to allow for a natural cold stratification of the seed and germination the following spring. Given the amount of bare soil left behind by the smothering annual joint grasses, the Henrys also used some temporary cover crops to fill gaps.

After all this work — two seasons of planting plugs and seeding — and well into the third year of active management, the Henrys were not seeing very promising results. Many of the plugs seemed to have disappeared or were matted over by annual weeds, despite cool season cover crops. They were just about ready to throw in the towel when they decided to isolate an extensively plugged area of the meadow from the threat of deer browse by installing a three-wire offset electrified deer fence.

Beware of Deer

Cardinal flowers
Cardinal flowers provide important nectars for hummingbirds and other pollinators.

The result was extremely encouraging. Many plugs that had seemed all but swallowed by the weeds and deer suddenly reappeared. All the perennial forbs, thought dead, emerged robust. The cool and warm season grasses like Deschampsia and Panicum grew so vigorously that the competing annual weeds were significantly reduced.

In the end, it was not one management strategy, but an integrated approach — a lot of patience by the Henrys along with curbing the constant deer pressure on the native flora — that led to this ecosystem’s success. This year, the Henrys intend to fence in the entire wet meadow and look forward to seeing the fruits of their labor and investment. Hopefully, the old adage about establishing meadows — first year it sleeps, second year it creeps, and third year it leaps — will prove true, even if it’s off by an extra year.

For this wet meadow habitat enhancement project, the presence of seasonal hydrology and legacy seed bank proved to be extremely helpful and fruitful. The site is not unlike many others throughout southeast Pennsylvania and the Piedmont. A great many of these wet meadows sit fallow or unattended. With the right management and time (plus learning some stern lessons from both botany and the environment along the way), these wet meadow habitats will increase in ecological value and functionality.

That’s the power of native plants — when they are planted as interconnected tapestry, they can transform a landscape into a restored ecosystem.

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