May 15, 2023

Garden Swale: How It's Doing

Photo from Feb. 2022. Swale after a three inch rain. Making of pictures here.

About a year and a half ago, we dug a garden swale. The purpose of a swale is to collect and store rain runoff. It's dug wide and deep for that purpose. The stored water slowly seeps into the ground and hydrates underground. This is important because during a drought, even a good rain may not saturate the ground deeply. So, a three inch rain may only get the top three or four inches of soil wet. I learned this by digging around in the soil with a shovel after a rain.

A good swale combined with good rains will gradually make a difference in the soil moisture level. According to permaculturist Bill Mollison, it takes several years, but it eventually the deep soil will remain hydrated, even during droughty spells. This will only be our second summer with our garden swale, so I don't think we'll see it's full benefit yet, but I'm hopeful.

What I really want to show you, though, is the swale berm. The topsoil we removed went for a hugelkultur experiment (more about that in this post.) The subsoil became a berm on the downhill side of the swale. I didn't want it to become overgrown with weeds, so I pulled out my garden seeds and planted a mix of old herb, flower, and cool weather greens, along with clover and a winter bulb forage mix. A year and a half later, it's still thriving.

This is what I see when I first walk to the garden. Swale on the right.

Looking back from the other end of the swale. Berm on the left.

The chicory and clover are predominant, but there are a few other interesting things here and there.

California poppies

Red clover


Bachelor Button


Collard flowers

Radish flowers

Summer's very first chicory flower.

Comfrey, which is growing under a pear
tree at the base of the berm rather than in it.

A couple of weeks ago, I planted black turtle beans in the bare spots, because I don't like to leave bare soil anywhere.

Something has been munching on my black turtle beans.

What amazes me is how well everything has done considering that the berm is mostly clay subsoil. Being raised, it does tend to dry out fairly quickly during our hot dry spells in summer. What has survived and thrived, has done it without help from me: no watering, no compost, no mulch, just a little chop and drop. Amazing, isn't it? I'm thrilled that it's thriving.


Rosalea said...

That is beautiful, Leigh. The first 'unknown', is a Bachelor Button (Centaurea cyanus). Thank you for reminding me about comfrey. Another plant I want to establish here.

Leigh said...

Rosalea, thank you! I'm updating my captions.

I love comfrey, but have had a hard time getting it established here. I hope you do better than me!

Sandi said...

So beautiful.

Leigh said...

Sandi, thank you!

Tisha said...

I think the yellow mystery flower is coreopsis.

Leigh said...

Tisha, I think you're correct! Thank you! Updating caption.

Ed said...

You swale posts have definitely made a blip on my radar. I don't yet have a practical place to try them out, because our garden area is flat, but perhaps someday they will come in handy.

To your point about the subsoil drying out, we received 0.4" of rain Thursday night and went down to our garden early Friday morning. I fully expected the soil to be slimy to walk on top. However it has absorbed every drop of that rain and actually had a dry feel to it. The only hint that it had rained was a perennial puddle nearby with a clay bottom had water in it and that the top soil under the crust was a shade darker.

Toirdhealbheach Beucail said...

Leigh, I enjoy the fact that you effectively have a lovely wildflower garden that you are completely managing without additional inputs. That is amazing!

Leigh said...

Ed, I wonder if there is even a subtle contour to your place. Even so, I suspect there is an answer for flat land. I think mature swales can offer a lot of relief from drought and irrigation.

TB, I'm amazed as well! I still have a few weeds in the berm, such as grasses, poison ivy, and blackberries. I'm hopeful I'll be able to defeat them eventually.

Michael said...

Swales are wonderful. Thanks for sharing!

Even an almost unnoticeable grade can benefit from them.

How's the h├╝gelkultur doing?

daisy g said...

What a great experiment! Mother Nature does it all without much help from us!

wyomingheart said...

What a great post! We have that same type of soil, here on the ridge. I’d call that a success story! No maintenance?…Bonus !

Leigh said...

Michael, I agree about swales and grade. Every little bit helps!

The hugelkultur is doing just as well as the swale berm (I pretty much planted it with the same seed mix). I've planted cowpeas and winter squash in the bare spots. I'll have to do an update soon!

Daisy, I love it when an experiment is a success. I've had enough failures to really appreciate them!

Wyomingheart, thanks! Digging swales into clay subsoil makes for excellent water catching, with slow seepage downhill.

The only place I'm having trouble with maintenance-wise, is the edge.

Michael said...

Leigh, what's the problem with the swale edge?

Erosion? Details please.

Leigh said...

Michael, I mean where the berm meets the "path." That's where the berm is subject to what I call grass creep. I have the same problem in my bordered garden beds. The grasses lean over and drop seeds into the berm or beds. Or with something like bermuda grass, the stolens creep underground and start to take over. I suppose ideally, I could border the entire berm and keep the path mulched, but that isn't going to make it to the top of the to-do list any time soon!

Leigh said...

I hit publish too soon. This happens at the swale edges too. It isn't so much erosion, as plants trying to invade, like poison ivy or black berry brambles. The grasses do the same thing. Keeping them from invading the swale is ongoing maintenance.

Michael said...

Leigh it is hard to fight grass creeping. Between the airborne seed dropping over any edging and the underground visitors :-).

Have you given thought to weeding geese?

A swale covered in grasses still works well but not as aesthetic as your lovely pictures.

Poison ivy I carboard them to die for lack of sunshine. Thorny Blackberries I tend to take cutting from as I value their fruit, pollinator attracting and making a leave me alone hedge against wanderers.

Leigh said...

Michael, I've often thought that if I had only one thing to do, then I could do it well. Seems like most things around here get "a lick and a promise" and then it's on to something else. If I were to name our homestead, I'd call it "Wildside" because that's what it always looks like! The good thing about the poison ivy and blackberries is that the goats will eat them. I hope that either by continually pulling them they'll eventually be gone, or else the good stuff will shade them out.

Ed said...

I guess technically we do have some swales. We have always mounded up the center of our garden so that it drains better when we have really wet years. Three of the edges tend to collect water in the resulting low spots and are slowly absorbed back into the ground.

Leigh said...

Ed, well, there you go. I figure the more water the ground can hold, the less I have to irrigate.