Overseeding Prairies

What do you do with a prairie that’s missing most of its plant species?  In some cases, good management can allow some plants to seemingly return from the dead.  In others, though, the species are gone and – especially if the prairie is isolated from others – they’re not coming back.

When the species are gone, the only remedy is to bring them back.  Seedlings are one way to do that, but can be expensive if the area to be restored is very big.  Harvesting seeds from nearby prairies and throwing them out is probably the most cost effective strategy. 

An overseeded prairie north of Lincoln, Nebraska.

However, most people who have done prairie overseeding share a similar tale of the results.  It usually goes something like this.  “I threw the seeds out and nothing happened.  For several years, I looked every year and never saw any new species come up.  So I gave up.  Then, 5 years later, I happened to go by the site and there were new plants everywhere!”

Exploring why and how overseeding works (or doesn’t) is something I’ve been spending a lot of time on lately.  I’ve got several research projects underway that, I hope, will help shed some light on this topic.  There are some things I think I’ve learned that I’ll share in a later post.  In the meantime, I’ll add my own story to the raft of others.

The above photo was taken this fall at a site we manage north of Lincoln, Nebraska.  It was a brome-dominated hill prairie – if prairie is the right word – that had few species other than smooth brome.  Some goldenrod, heath aster, yarrow, and a few other scattered plants that are good colonizers and/or resistant to overgrazing and herbicides.  We burned the site in about 2001, sprayed it with Glyphosate in April when the brome came up, and then seeded it with a diverse mixture of prairie species.  The next year, the brome was back in full force and it looked like nothing had changed.  Over the next several years, it looked exactly the same, except that every once in a while I’d stumble onto an isolated plant of prairie cinquefoil or Canada milkvetch that had obviously come from our seed.

In the last couple of years, I started noticing more of those prairie species, and warm-season native grasses started becoming more abundant as well.  Then, last season, we brought in a bunch of cows and grazed the site for the entire year – down to the proverbial “golf course” height.  And this year, the prairie looks marvelous.  It still has some brome, but it’s not dominant.  I’d love to see some of the species like compass plant and Canada milkvetch be more abundant, but they’re there.  And it looks like a prairie.  Was it the grazing that released everything?  I’m sure it helped, but the prairie was headed in the right direction already.  Why did it take so long?  What finally triggered the species to show up? 

Stay tuned.  I hope to have more ideas on this soon.  And please share your own!

1 thought on “Overseeding Prairies

  1. Hi Chris,

    Was looking back through some older posts and saw this one. Another topic that has a lot of potential application on a larger scale for prairie reconstruction, restoration, management. Had a very interesting experience with this at Rainwater Basin Wetland Management District. In the late 1990s, I started finding places on Waterfowl Production Areas that had more than the usual 5 species of warm season grasses that had been seeded. I was finding leadplant, purple prairie clover, upright coneflower, compass plant, and other species that do not find their way back on the wind. Checking the records, their was no indication that these species had ever been seeded and historical aerial photos documented that the sites were farmed when they were purchased. So something, or more likely someone, had harvested seeds and scattered them on these WPAs. I asked the staff that had been there the longest, one almost 30 years. After he thought about it, he recalled a seasonal biological technician that had a strong interest in prairie. He “caught” him a few times collecting native seeds in the late summer/early fall from some remnant prairies on WPAs and suspected he had been doing that both seasons he worked there. Unfortunately he could not remember his name or how to get ahold of this seasonal biotech (If someone out there is reading this and you are the prairie enthusiast from about 1980, 81, 82, 83 that worked at Rainwater Basin Wetland Management District, I would love to visit). I would be willing to bet the seeds were collected and then scattered by hand on a relatively small scale. I do not remember finding these species on these sites prior to prescribed burning or prescribed grazing, but only after. There were no records in the files either of finding these native forbs prior to the late 1990s. These native forbs made up a decent part of the plant community, not just a plant here and there. From this experience, I now take the optimistic approach that if we get the seed rain going, give it time (10 to 15+ years), and follow up with the other ecological processes of fire and grazing, these species will find places to express themselves. One of the major benefits I have found of conducting our own seed harvest is that I am not as leary to get the seed rain going as I would be if I had to show some success in 2 or 3 years by purchasing and interseeding/overseeding some high dollar seed. I have also taken this interseeding method into the wet meadow/sedge zone. Many temporary/seasonal/semi permanent wetlands were farmed during extended drought cycles. A number of the wetland species survive in the seed bank or can blow back on the wind, but many just like in the uplands, don’t make it back on their own. In particular, sedges and wetland grasses appear to have a very difficult time surviving the plow. Overseeding, followed by prescribed burning and prescribed grazing in wet meadows, into existing wetland vegetation, has worked well for me. Instead of the 10 to 15 years required for the uplands however, wet meadow can establish much more quickly due to adequate water. This wet meadow zone also happens to be some of the worst sites for invasive species such as Canada thistle, and the competition provided by the sedges and wetland grasses helps to control this species. I have now started to think more of overseeding as one of the major historical ecological processes, along with fire and grazing. The seed rain (overseeding) occurred on an annual basis. Nearly every year for some species, less frequently for others. The current model used by most of a one time seeding does not replicate the historical annual “seed rain” that occurred for most species.


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