Rehabilitating Middleton Hills Prairie

 We've been working for the Middleton Hills Neighborhood Association for 11 years now, and I thought this might be a good opportunity to share an example of the work involved in, and successful results from rehabilitation of a failed prairie planting.

Here's the location. Take a visit if you're in the area, it looks spectacular now!:

2010: Introduction

When I first saw the site in fall of 2010, the "prairie" was literally more weed than it was prairie plants. Though there were native prairie plant scattered throughout from the seeding done a few years prior, I would say that coverage was 80% or more weeds and invasive plants, only 20%, or less, natives. Unfortunately, this is not an uncommon result from poorly planned and implemented prairie plantings done by folks who don't have a background in ecological land management. When painting a prairie, three things are critical:

1. Thorough site preparation in the growing season, or two before the planting to eliminate weeds and invasive plants
2. Spreading a sufficient amount of a diverse native seed mix that is tuned to the exact soil and sunlight conditions of the site
3. Thorough stewardship, weed management, monitoring and interseeding, if needed, for several years after planting.

This site had none of that, and the results were predictable. I informed the representative of the Neighborhood Association who was showing me around that it would be faster, easier and less expensive if we just tilled the whole site in and started from scratch following the guidelines above. The Association didn't want to do that, they wanted to retain what they had so far. So, I developed a plan to start getting this prairie on the right track.

In the bottom here you can see a lot of birdsfoot trefoil, an invasive perennial. A few of the taller plants are prairie species, including New England aster and false sunflower. Indian grass flops over as it has no prairie neighbors to lean on!

The walking path through the prairie was itself a problem. A common issue at prairie edges is lawn grasses spreading into the prairie. Fescue is pretty easy to control with fire, but Kentucky blue grass (not from Kentucky!) is an aggressive spreader and difficult to control. Kentucky blue grass is one of the most widespread invasive plants in North America. 

You can see the native Indian grass in th background, most of the grass in the foreground is exotic fescue. The light green plant spreading in the center is western ragweed. This rhizomatous perennial was a new one to me, it was probably brought in on the tires or tracks of the equipment used to establish the above power lines. It seems do do well in this area where the soil is particularly compacted.

So much Canada goldenrod! Though this species is native (and does provide a great nectar resource for pollinators), it is very aggressive and can spread to form monocultures that exclude all other species. Though this species is an important one to suppress, it would have to wait as we had bigger fish to fry in the mean time.

2011: Work Begins

We set up an annual budget that the association could set-aside for prairie maintenance, and did as much as we could each year within the budget, with the goal of slowly eliminating invasive plants and weeds, and introducing native plants over time. Below are some photos taken in July of 2011, of the results of our first efforts at weed management during June of 2011. 

In the early years, we often used an herbicide called Milestone. Plants in the aster family (Asteraceae) and legume family (Fabaceae) are particularly susceptible to this herbicide, so is leafy spurge. Many plants in other families are not harmed by this herbicide. This allowed us to be very selective when trying to control Canada thistle (aster family) and birdsfoot trefoil (legume family). However, a lot of prairie species are in those families too, so we had to carefully work around the remaining natives.

Western ragweed carpeted large areas in the prairie, with very few native prairie plant surviving in-between. This species would prove to be a bit of a puzzle to develop a control strategy for. Not only does this species spread quickly by rhizomes, it seems to be strongly allelopathic.

Dead leafy spurge. Note how the Milestone had no impact on the grasses around it.

Birdsfoot trefoil creeping from the lawn path into the prairie. We're going to have to do something about that.

A patch of Canada thistle sprayed while working to avoid surrounding vegetation.

Here I sprayed Canada thistle on either side of these couple of native plants. Notice how the wild bergamot on the left, which is in the mint family is completely unaffected. On the right is false sunflower, which is absorbed a small amount of the Milestone either though drift or through the soil. It is injured by this, but will recover and look normal the following year. If you look carefully at other photos in this series you can see other native plants with curling stems, almost all of which survived.

It wasn't all bad news! Here we see wild bergamot, false sunflower and butterfly milkweed blooming. There is also some rosinweed in the upper right, and stiff goldenrod to the lower right.

Prickly lettuce and motherwort are also weeds, but they are not as aggressive or impactful as some other species, and we had to let them be for a while while we got the worst invasive species under control.

Its a challenging situation when you have reed canary grass mixed in with native plants like this. Carefully timed treatments are important to harm this aggressive exotic grass while minimizing harm to the native plants. Another good example why it is important to plan ahead and do a good job establishing a prairie in the first place so you aren't face with these challenges.

2012: First Burn!

We conducted an early burn in March of 2012 to clear off existing vegetation and to encourage the weeds to come up. Why do we want to encourage the weeds? By creating conditions that promote the growth of exotic cool-season grasses and weeds like birdsfoot trefoil and Canada thistle in April, we could treat them with herbicide before most of the native plants emerged for the season and while all of the plants were small and separated, making spot spraying the weeds and avoiding the native plants easier.

Note also that 2012 was a drought year. We had some 80-degre days in March, which allowed for such an early burn, but also left the vegetation looking sparse and dry by summer. Native plants are adapted to our local climate, including periodic droughts, so in the long run I think this favored the prairie species over the invaders.

Up until now, the biggest priority was eliminating invasive plants. Now that we were seeing progress on that front, I believe the fall of 2012 was the first year we started to seed more prairie plants back into the site. Interseeding would continue to a greater or lesser extent, for every year there-after.

First Burn! Nice clean control lines in a tight urban environment. The crew did a great job that day. You can see Joy in the upper-right putting down a wetline in advance of the fire.

Pale purple coneflower, the only Echinacea native to Wisconsin, is really starting to thrive after the burn and competition from weeds being removed. Sarah does some hand-weeding in the background.

2013: Eliminating Sources of Weeds

Instead of another burn in 2013, I decided the best use of the budget for the year was to eliminate the weed source that was the mowed path down the middle. So we used herbicide to kill the vegetation in the path (and where they had spread into the adjacent prairie as well) and covered it with hardwood chip mulch shortly there after. That summer we were able to start to do more manual weed management.

Mulched path eliminates some of the edge effects of having such a small prairie in an urban area, and directly eliminates the source of many weeds.

Athena works on pulling a stubborn wild carrot. It is not uncommon for biennial weeds like carrot and sweet clover to be abundant the growing season after a burn We pulled thousands of wild carrot on this stewardship visit and the following one.

2014: Recovery begins

Another Burn in the spring of 2014, it wasn't as dramatic since we had killed so-many weeds, there was less fuel for the fire to burn. We also conducted the burn fairly late to have the greatest impact on exotic cool-season grasses and non-native weeds. We followed-up with the same early-season weed treatment. The burns themselves had a lot of impact, encouraging native plants and weakening the weeds. This combined with four seasons of fairly aggressive herbicide application were beginning to pay-off.

Ray checks the fireline. You can see the exotic cool-season grasses already greening-up in the prairie. They will be weekend by this fire.

Compare this with the 2012 image of pale purple coneflower. 2014 is so much more lush!

First blooming compass plant.

A variety of prairie plants filling in a real that used to be weeds! Still, to my land-manager eye, I can't help but see the small yellow flowers, which are birdsfoot trefoil, and the reed canary grass seed-head at the bottom.

I remember feeling pretty victorious when I took this photo, a swath pf prairie plants, butterfly milkweed in the foreground, pale purple coneflower in the background, along with fleabanes and penstemon.

Spiderwort! Still some little yellow dots of birdsfoot trefoil among the vegetation though. We're on the right track, but there is more work to be done.

2015 to 2019: Steady Progress and New Challenges

We had gotten the worst of the weeds under control at this point. The patient was out of critical condition and now it was time to move them to physical therapy. Another project manager, Rob took over for me at Middleton Hills for several of these years. He was able to back-off on the use of herbicide substantially, almost all of our work at this point was manual and mechanical control of individual invasive plants. With one exception; we used a very targeted technique called leaf-spritzing to begin to control the Canada goldenrod. The approach involved using just a couple drops of concentrated Garlon 4 herbicide (the same  concentration we used to kill buckthorn stumps) on each stem of the clone. Using this approach, we were able to push back the large areas of goldenrod without harming any neighboring prairie plants. 

Rob also focused much more on adding more native prairie flora to the site through annual fall seedings and even planting some live plants as the budget allowed.

Dramatic spring fire in 2015.

The prairie begins to fill in more completely after several years of interseeding.

A red admiral butterfly nectarine on pale purple coneflower.

A stand of stiff goldenrod in early-fall 2015 where once we had nothing but Western ragweed!

This area ws previously solid Canada goldenrod (same utility pole from the 2010 image above). The good news is that we have spiderwort (blue flowers) coming in along with foxglove beardtongue (white flowers). The bad news is that there is also a lot of curly dock filling in the gaps where goldenrod used to be. More weed management and more seeding are needed. We use a Parsnip Predator to pop out the curly dock and remove the plant, and the thousands of seeds on each, from the site.

2020 and 2021: Glamor Shots

We have largely moved into the maintenance phase of managing this prairie. These years we did regular but short visits to control many of the above-mentioned weeds in the prairie at just the right time for each. We focused on continuing to beat back the Canada goldenrod, and the weeds that came-up in their place. We also were able to work on improving the surroundings around the prairie. In January of 2020 and 2021, we cleared invasive buckthorn, honeysuckle, mulberry and boxelder from areas in and around to the prairie to reduce their impact (mostly via shade) and potential to invade.

Wild lupine.

This patch of reed canary grass avoided our wrath for a while, but we took it down in mid-May 2020. Photo was taken about 2 weeks after treatment. On the left we used a glyphosate-based herbicide (AquaNeat), on the right we used a grass-specific herbicide sethoxydim (Poast) which took longer to act, and was somewhat less effective. Below right was my accidental control group, where I forgot to spray it.

Wild bergamot, switch grass and false sunflower

Hoary vervain among other, previously mentioned prairie flowers.

Monarch nectarine on purple prairie clover.

According to Seek, this is a black and gold bumblebee feeding on wild bergamot. She was a big one!

Fresh mulch! Hardwood chips are more durable than shredded bark mulch, and easier to walk on, though they can wash-away more easily in areas of water flow.

And the Future?

In the short term, we still have perennial weeds to control. Birdsfoot trefoil persists, Canada goldenrod is on the decline, but not gone yet, and Western ragweed has made an alarming comeback. Some early-fall mowing followed by a carefully targeted late-fall spot herbicide should go a long way towards control of these. We will burn again next spring and follow-up on these, as well as remaining exotic cool-season grasses.

Over the next couple of years the amount of our work needed on this site will begin to diminish. We should get to a point soon where we conduct a burn every 2-3 years, replace the mulch in the trail every 2-3 years and have just 3 short visits throughout each the growing season to keep the weed population very low. In a site like this, a very small (1 acre) prairie in an urban environment like this there will always be an influx of weeds.