Does over-seeding prairie plantings work?

By Bill Kleiman, Project Director of Nachusa Grasslands, The Nature Conservancy

Have you planted seed into an already established prairie planting, trying to increase floral diversity?  You had that warm hopeful feeling. Those tiny seeds in your hand soon to be germinating.  New flowers blooming in your restoration.

Did what you plant ever show up?  Most of us have examples of where the seed planted did eventually produce new populations, but more often we shrug when asked.

Way back in 2009 I had this study question: What is the best way to over-seed an already established prairie planting to increase its diversity?  Below is the random block we set up with four treatments and  a control.  I explain the block below.

This was in an established prairie, with reasonable forb diversity, rather thick in warm season grasses.  Look at the top row of cells.  In cell A1 we worked up the prairie sod with a disc, then raked it with a harrow, and then seeded a rich and abundant mix of seed, well over 50 species at a heavy pounds per acre.  Would this cell turn out the best?

In A2 we only added seed.

In A3 we harrowed, seeded, and then in mid-summer we sprayed with Poast grass herbicide.   Would the grass herbicide set back the Indian grass and big bluestem and make space for our seed to grow?

A4 was the control with no seed added.

A5 we harrowed and seeded.

The B row and C row are the same setup but not in same order.  This is called a Random Block study.

Below photo looks down at the block when we set it up.  It was burned before we did anything.  You can see the harrowed and disced cells.

Below is the disc in one of the cells.  We worked up the prairie sod several inches deep.


Ten years later what do you think we see when we walk along this experimental block?

All the cells look the same to me.  Elizabeth says she saw some subtle differences.

The experiment is ongoing.  We are looking for a grad student to adopt this experiment and collect the vegetation data.

My takeaways on adding seed to established plantings is this:

It takes a long time for the seed planted to produce a noticeable sized plant.  There are exceptions where plants show up in just a handful of years after addition, but you should expect a decade, or two decades, to get the establishment you want.

Yes, you should add seed to those prairie plantings.   Many species you want to see in your restorations will not blow in, nor be dropped in by birds flying over, or carried in the fur of rabbits or deer or mice.  It will be you planting the seed.

Patience is a prairie word.

Below are the experimenters in 2009:  Susan Kleiman, 9 year old Leah K, and myself, Bill K.    I coaxed Leah with promises of fun science.  She is now 20 years old majoring in plant ecology.

We did three of these same blocks.  More details here:–resources.html

If you want to see the seed list we planted look to planting 91 and 92 here:


About Grassland Restoration Network blog

Bill Kleiman publishes this blog. Bill's daytime job is manager of Nachusa Grasslands. We are looking for guest authors on various topics of grassland habitat restoration. Contact me with your ideas or drafts.
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5 Responses to Does over-seeding prairie plantings work?

  1. Paul Brewer says:

    Great post Bill! Even after waiting those 20 years, there is also a ebb and flow in the prairie. Some years, some plants bloom like mad – then you might go a few years and think those plants have “dropped out”, only to have them show back up in good numbers again.

    Thanks to you and guys like Chris Helzer for experimenting with a wide array of trials to see what is working and what is not. I have seen too many people give up when what they needed most is that key ingredient – patience!

  2. Paul Gordon says:

    Great teaser for a very important study question. Please let us know the results!

  3. adam thada says:

    Thanks for posting this Bill. Looking forward to seeing more details! I’m wondering about the burn history from 2009-2020.In a very short term experiment (1 season at Taylor University), I found that 2 applications of grass-specific clethodim was enough in the first growing season after over-seeding to greatly increase the amount & size of seedlings at the end of year 1. We have longer-term data too, though the stewards ended up repeated the clethodim applications for several years afterwards. I wonder what it would have looked like with a single year’s applications.

    • Adam, We have three of these Random Blocks and our fire return interval is very short, no more than two years. I think a double spraying of grass herbicide sounds good, but we kept it to one on each block for consistency. We know of a few places where grass herbicide seemed to open niche space for seedling establishment. Perhaps you could write up a blog post for us. It can be short. You can link to a longer document if you wish.

  4. Pingback: news round up, end of summer edition – Ecological Relationships

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