Restoring Native Diversity in a Grass-Infested Wet Prairie – by Nate Simons

One of the most aggressive plant invaders in a sedge meadow or prairie fen ecosystem is the ubiquitous reed canary grass. Long planted (and abundantly escaped) as a pasture grass for soggy soils, reed canary grass is adventive from Europe. The rhizomatous grass spreads by underground, horizontal roots to quickly form a dense sod that outcompetes and displaces almost all native wetland plant species…often times forming complete monocultures.

Restoration of sedge meadows and prairie fens infected with this exotic, invasive grass is difficult and time consuming. A complete cover of this grass in a restoration project usually requires complete chemical eradication of the sod. If, however, the reed canary grass has not yet formed a complete sod and native sedges and wildflowers still remain, another process may be employed to recover and promote the native vegetation.

Year 4 of mowing and spraying reed canary grass at Div. of Nature Preserves' Marsh Lake Nature Preserve. Sedges and wildflowers flourish where reed canary grass once dominated.
Year 4 of mowing and spraying reed canary grass at Div. of Nature Preserves’ Marsh Lake Nature Preserve. Sedges and wildflowers flourish where reed canary grass once dominated.

Given that reed canary grass possesses two sets of buds on their rhizomatous roots (buds that produce leaf shoots in the spring and a different set of summer-dormant buds that produce leaf shoots in the fall), control of the grass is tricky. The use of a grass-specific herbicide (clethodim is the herbicide of choice and is labeled for non-cropland areas) allows the restorationist to suppress the growth of the grass without harming the sedges and wildflowers. If conditions are right (no standing water…many fens and sedge meadows have saturated soils with no standing water), the herbicide can and should be applied two times a year.

The process looks like this:

  1. Burn the sedge meadow in the early spring.
  2. Apply grass-specific herbicide when the reed canary grass reaches ankle-to-shin high (April). The herbicide must be mixed with a crop oil or methylated seed oil to penetrate the waxy coating that the leaves naturally possess. This application suppresses the early leaf growth that emerges from the first set of buds.
  3. Mow the sedge meadow in late August (yes, a small tracked skid-steer loader can rumble across the quaking, soggy soil as long as enough native sod forms an interwoven mattress of roots) . The late, dormant buds then produce new leaf shoots.
  4. Apply grass-specific herbicide and seed oil solution when the grass again reaches ankle-to-shin height (late September and early October.

This process must be repeated for a number of consecutive years until the strength of the rhizomes is completely diminished and the native sedges and wildflowers moves into the resulting soil space. Skipping a season almost assuredly means starting the process over. The process often takes more than five years. However, with repeated semi-annual applications of grass-specific herbicide in conjunction with late summer mowing, the result can be an abundance of and diversity of native sedges and wildflowers. Upon a soggy walk through the late summer prairie, ones senses will be thrilled with the sights, sounds, fragrances, and beauty of a gloriously-rich and uncommon ecosystem. And the native pollinators and other fen-dependent animal species will thank you profusely when they re-discover home.

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