Solarizing a Slope- Erosion concern

I finally figured out what to do with my impossible-to-mow steep front slope... SMOTHER IT TO DEATH! And re-plant with a native pollinator mix. I've practiced smothering and seeding in a smaller area so I feel ready for this, except for the slope part.
If I follow my current technique of smothering in the summer, tilling in the late fall, and seeding after killing frosts, then I end up with a steep bare-earth slope all winter until the seeds start germinating in the spring. Which is not only an erosion concern, but also those seeds are going to get washed downhill.

These seeds don't want to be covered (mulched) because a lot of them need light to germinate (along with the cold stratification of winter, hence needing to till and apply in late fall.)

So one solution might be to just cut the existing grass/weeds really really low, leaving the roots in the soil. Then solarize to kill the roots/crowns and cast the seed blend on top. Tilling would be very difficult on this slope anyhow. Does this sound like a good compromise? Will the remaining grass and weed roots be enough to prevent erosion, but not too much to keep the seeds from good soil contact to germinate?  

Definitely better than tilling, but it depends.

How prone to erosion?

When is the rainy season?

Could you add swales or other erosion control?

Could you plant an annual cover crop to hold the soil and prevent weeds from sprouting?

I sympathize with you because I have a lot of weedy slopes that are full of invasive, noxious weeds and I am trying to turn those slopes into something sustainable. I have found that seeding the ground doesn't work so well because the seeds get washed down the slope, eaten by mice or the seedlings get pulled up by birds.  A couple ideas for you that I am trying. One is starting your seeds in flats or cells.  Most native, meadow flowers and grasses want to go through winter outside so I put my seeded flats/cells out on the back porch all winter.  The grasses I put in flats and the biennials/perennials I put in deep cells to accomodate the taproots. Some sprouted before winter set in and some after but most of them survived and I've transplanted a lot of them already.  Beware, the mice who come to eat your seeds though! Okay, this approach is a lot of work, I know, but it seems to work a lot better than just strewing the seeds on the ground.  The other thing I'm doing with the slopes is planting low-growing plants that are drought tolerant, are not tall, spread a lot and are good for erosion control (low-growing sumac, juniper, sarcocca and rosemary work in my zone).  

R Scott wrote:Definitely better than tilling, but it depends.
How prone to erosion?
When is the rainy season?
Could you add swales or other erosion control?
Could you plant an annual cover crop to hold the soil and prevent weeds from sprouting?

How prone- it's steep enough that a bare slope would erode quickly. I guess the seeds washing away is the bigger concern.
Rainy- Whenever Missouri feels like it! Heaviest rains in summer storms but early spring rains would still have a washing effect.
Erosion control- no swales possible here. The slope is maybe 12 feet top to bottom coming up from the roadway.
Cover crop- Anything I seed would have the same issues/sprout at the same time as the pollinators I want to grow.

If that's the case, I would do it in stages.  Either spots or narrow strips on contour, whichever work for your supplies and plants.
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R Scott wrote:If that's the case, I would do it in stages.  Either spots or narrow strips on contour, whichever work for your supplies and plants.
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There's a thought! Strips on contour could work. Any thought/reasoning on top to bottom or bottom to top?

Have you thought about growing a ground cover that pollinators would love?

I always think about creeping thyme but wild strawberries, Fragaria vesca, might be good, too.

In the fall you might be able to sow the native pollinator mix and everyone will be happy.

Anne Miller wrote:Have you thought about growing a ground cover that pollinators would love?

I always think about creeping thyme but wild strawberries, Fragaria vesca, might be good, too.

In the fall you might be able to sow the native pollinator mix and everyone will be happy.

Don't I still run into the same problem with cover crops? Since I'd still have to remove all vegetation before growing a cover crop just like I would before growing the pollinator mix.
Am I missing something with the suggestion of cover crops?

can you leave your solarizing material on over the winter and do the seeding plus whatever else the following spring? that would at least avoid bare earth over the winter.

greg mosser wrote:can you leave your solarizing material on over the winter and do the seeding plus whatever else the following spring? that would at least avoid bare earth over the winter.

Well I would, but the seeds need to get the cold moist stratification from the winter.

Matt Todd wrote:

R Scott wrote:If that's the case, I would do it in stages.  Either spots or narrow strips on contour, whichever work for your supplies and plants.
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There's a thought! Strips on contour could work. Any thought/reasoning on top to bottom or bottom to top?

Whichever works for you.  I would do several strips to speed up the transition.

Matt Todd wrote:

greg mosser wrote:can you leave your solarizing material on over the winter and do the seeding plus whatever else the following spring? that would at least avoid bare earth over the winter.

Well I would, but the seeds need to get the cold moist stratification from the winter.

I can not count on decent frosts during the winter here so I cold stratify in the fridge or freezer.
Can't direct sow most things in my clay soil so start in pots and plant when they're big enough to cope.

Any help ?

I would also try to do it in strips.  I guess I wouldn't really start at the bottom or the top, I would make stripes all the way from top to bottom and plant them all at once.  I think if you use a roller after planting, you could keep most of them from washing away.  If you get a huge rain, probably nothing will work, but for "regular" rains, you would probably be okay.  A very thin layer of straw after seeding would also help a lot if you can get it to stay on the slope.

Another idea may be to make very small "terraces".  If you are planting with wild flowers, you won't have to mow.  By very small, I mean so it looked like steps up the slope.  No idea what size you are talking about, or what equipment you have, so maybe that isn't practical.

Before plastic geo textile fabrics, they used burlap.  I remember helping grandpa fill potato sacks about a quarter full of dirt and seed and loosely stack them in a ravine he was trying to fill in with grass. Not sure where to get burlap sacks in quantity these days.

Anne Miller wrote:Have you thought about growing a ground cover that pollinators would love? I always think about creeping thyme but wild strawberries, Fragaria vesca, might be good, too.
In the fall you might be able to sow the native pollinator mix and everyone will be happy.

Matt Todd wrote:]Don't I still run into the same problem with cover crops? Since I'd still have to remove all vegetation before growing a cover crop just like I would before growing the pollinator mix.
Am I missing something with the suggestion of cover crops?

My thought was to solarize, plant the strawberries this spring for erosion control, the sow the pollinator seed mix in the fall for next spring.

I see no reason to remove the strawberries. If they can't co-exist with the pollinator seed mix, nature will work everything out.

Sounds to me like this would make everyone happy.

For the slope in my yard, I did not till after solarizing, so the dead weeds/grass helped hold the seeds in place. It was years ago, but I am pretty sure I used a roller to help press the seeds into the ground for good soil contact.

I have a tendency to seed on the heavy side, and had no problem getting the meadow started.

My slope was moderate and easy to work on. If I had a steeper slope, I might consider a ditch, berm or swale at the top to help reduce water from running down the slope in big rain events.

Also, if you don't have a roller to press the seeds into the soul, your feet would work just fine, but might take a bit longer.

I am starting my third solarized meadow this spring, and I never tilled any of them. As long as you do something to press the seed to get good soil contact, I don't see the need to till. The meadow plants don't seem to mind the compacted soil, and loosen the soil over time.

Good luck! My wife & I both love the meadows, and we think the wildlife does too

Anne Miller wrote:
My thought was to solarize, plant the strawberries this spring for erosion control, the sow the pollinator seed mix in the fall for next spring.

I see no reason to remove the strawberries. If they can't co-exist with the pollinator seed mix, nature will work everything out.

Sounds to me like this would make everyone happy.

Ok, I follow you now. And I likely still have time in the season to do this. In fact, I recently looked at wild strawberry seed for ground cover elsewhere... and found it difficult and expensive to find! So much for my bright idea of just broadcasting those. I'd need to grow plugs.
I agree that native pollinators should be able to bust up through wild strawberry, especially if it's not such an established dense mat yet. I think the issue I'm having is trying to cover too much ground too fast. Which I can get away with when seeding flat ground but may need to temper my expectations on this steep slope.

I started a bunch of yarrow from seed and now I have 72 plants, along with 24 butterfly weed starts. Now I'm trying to incorporate these into the slope too (rather than planting them on their own somewhere.) Which complicates matters.

I'm thinking I can maybe apply the plastic for solarization and just cut holes to plant the yarrow and milkweed through into spots I'll manually weed ahead of time. They'll retain moisture well since the plastic will act as mulch, but one issue might be the increase in soil temps. One study showed clear plastic raising soil temp to 95 degrees F. Does anyone see this being an issue, or would the hole in the plastic keep the soil cool enough in the planting sites?

I would not advise punching holes through plastic and putting plants in it.  Plants' roots need moisture, air and depend on the abundance of living things in the soil to do their job. The roots are a delicate part of the plant compared to the stems and leaves above the ground. Solarization is intended to heat up the ground hot enough to kill seeds, which I don't think either the plant roots or the beneficial living things in the soil would like.  How about instead picking some areas on the slope to not solarize and instead doing some mass plantings of your starts? Planting them together would help crowd out future weeds, at least eventually.

Jen Swanson wrote:Solarization is intended to heat up the ground hot enough to kill seeds, which I don't think either the plant roots or the beneficial living things in the soil would like .

Yeah in hindsight, I can't have it both ways
This is what happens when you get excited, start a ton of plants, and then don't want to follow through with preparing ground to plant them in.

I agree with Jen. I wouldn't punch holes in the plastic, mostly because I don't think you will get a complete solarization. You really want to kill the weed seeds.

Matt Todd wrote:
This is what happens when you get excited, start a ton of plants, and then don't want to follow through with preparing ground to plant them in.

Haha.  I totally get that! I have hundreds of starts that need to get in the ground and the ground keeps growing more weeds where I just weeded! What's gotten me through this thus far? Good tools, diligence and an abundance of forgiveness