Solarizing Garden Beds

Dateline: 19 February 2016 AD

The experiment in last year's garden.
(click picture for larger view)

Last year I posted a photo essay to this blog explaining how I make raised beds in my garden (Click Here For Details). Then I posted another photo essay showing a new technique for holding sheets of plastic mulch and ground cover fabric on the beds and between the rows (Click Here For Details). I can report that my idea for securing the sheet materials worked very well last year. The only problem being that in a big garden, a lot of clothespins are needed. But I'm working on a less expensive, longer lasting alternative to using the clothespins, and hope to report on that breakthrough soon.

For now, I want to follow up on the idea of solarizing a garden bed using clear plastic. That was something I tried with two garden beds last year, as you can see in the above picture, and in this next picture...



The soil solarizing concept is very simple. You prepare the soil, layer a sheet of common clear plastic over the top, and let it be for a month or so. Heat from the sun "cooks" the soil under the plastic. Weed seeds are killed, pathogens are killed, fertility is released. There are lots of internet articles on the subject (with more specific information). Here is one: Soil Solarization

One drawback to soil solarization is that it takes time. If you need the bed for planting first thing in the spring, you don't have time to solarize the soil. But my garden is big enough that I have room and time to solariaze. In the picture above, my plan was to let those two beds solarize until early July and then plant my fall crop of Four-Day Carrots in them. And that's what I did, but with only one bed. I never planted the other bed to carrots. I wish I did, as our stored carrot supply here in February is getting low.

Anyway, here is a picture of those two solarizing beds later in the season...


If you click on the picture and take a closer look you'll see that some weeds have grown under the clear plastic around the edges. But nothing at all has grown over most of the bed. 

In this next picture I have removed the plastic prior to planting my carrots (in July)...


As you can see, most of the bed is well solarized, except for around the edges. But the edge weeds are lush and easily pulled...


The pulled weeds went into a compost pile. I then put a thin plastic mulch cover over the bed, and proceeded with my Four-Day carrot planting. I did not disturb the solarized soil beyond the disturbance that happened when pulling the edge weeds.

In these next two pictures you can see the carrot tri-plantings getting off to a good start. I do not recall pulling a single weed out of that bed for the whole carrot-growing season. Between the solarization and black plastic mulch, weeds were simply not a problem.



And here are a couple pictures of the carrots that grew in that garden bed...



In the final analysis, I am persuaded that solarizing a garden bed is a good and worthwhile thing to do. I will definitely be solarizing next year's carrot beds (the late-planted beds) and any other garden beds that lend themselves to this practice.

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More information about my carrot-growing strategy can be found in the chapters titled My System For Growing Easy Carrots and Tri-Growing Carrots (a curiously fun idea), which are in The Planet Whizbang Idea Book For Gardeners. Read those chapters, and watch the four, Four-Day Carrots videos on YouTube, and you will know everything I know (thus far) about successfully growing garden carrots.




13 comments:

Scott Cooper said...

I bought your book and read it, as well as the blog posts posts you referenced. I haven't tried the clothes pin method you describe but reading about it also got me thinking on whether there may be a faster/easier way of securing a cover like that. The few times I've attempted to do something similar, I used spare pieces of rebar I had laying around. I've thought about filling thin PVC or EMT with sand, capping it, laying it along the edge, and securing it with staples on the ends. Haven't tried it so I'm not sure how well it would work but I'm sure putting it down and taking it up would be easy.

Another method I thought of is, if you have fabric cut to size for a bed, you could put pairs of brass grommets in it (maybe every 4-6'?), then run the twine through each pair such that the twine mostly runs along the top of the edge of the cover. If the twine is pulled taught and staked at the ends, I would think it would hold it down fairly well. I hope I described that well enough to make sense...

I also remember reading about the trouble you had with your fabric unraveling/fraying. I bought some Dewitt fabric and used a torch to singe the ends but didn't like the results because I found it time consuming, the fumes difficult to avoid, and the fabric had a tendency to shrink/wrinkle up along the edge. I bought a can of Rust-Oleum LeakSeal which is a rubberized spray coating. I sprayed a line of it along where I wanted to cut the fabric, let it dry, then used scissors to cut along the line. The rubberized coating seemed to bind the woven fabric such that it wouldn't fray. Thus far, it seems to be holding up very well (though it's only been in the garden pathways since Fall). I'm sure there are people that would be concerned with leaching of chemicals (similar to the objections with using tires) from the coating but you be surprised how far a can of it went. I think I got a few hundred linear feet out of it as it doesn't take much. I can't imagine it to be too much of a concern when it's dry/stable and there so little of it so it doesn't concern me much.

vdeal said...

Herrick,

I'm looking forward to your alternative to clothespins. While they work they are a bit tedious.

Scott,

Heavy objects and pins will be defeated by substantial winds of which I deal with all the time. Now your idea of the grommets and twine has some merit and I'll think about how I could use it. As for cutting I think a hot knife cutter off of eBay would do the trick and be a lot easier.

Everett R Littlefield said...

Hi Herrick, For the last 5-6 years I have been holding my Agribon to the 3/4" pic pipe using the large "binder" clips used for holding stacks of papers together. They are holding up well after all tis time. The spring steel doesn't seem to rust and the handle wires are only slightly rusty after all this time. And they do have a very firm grip although I haven't tried them on a string or wire. We shall see this year as all my garden rows will be using them.

Last year I used your "pallet stakes for corner posts but this winter I ave bought 20, 20'x3/4" rebar and cut it to 24" pieces. Going to pound them in the ground to about 18" or so leaving me 6+or- a little to secure the baling twine to.

I also am going to be doing the solarization in a few places as I had a very poor potato crop this past year. Black and brown leaf spot that killed most of the plants when the spuds were pretty small. In fact I am going to till up a whole new plot for the spuds.

Going to go red the links to solarization right now. See ya later, Everett

vdeal said...

I think we're all chomping at the bit to get in the garden. My winter garden did okay for a first try and the kale, spinach and corn salad are all still fine and the rest will regrow as soon as the soon goes away - it can't leave soon enough! I've already got onions, celery and celeriac started. Keep the info coming Herrick.

vdeal said...

Well I meant to say "as soon as the snow goes away" - can't edit these comments.

Herrick Kimball said...

Hi Scott_
Rebar and other forms of weight is the kind of system I want to avoid. Mark Albert's clothespin idea on his cloche (page 71 of the book) is a step in the right direction. He says that if the string is stretched real tight, very few clothespins are needed to secure the material (row cover in his application). I'm probably using more clothespins than I really need to secure the fabric and plastic mulch.

I think the grommet idea has potential.

The unravelling of landscaping fabric was only a problem when I first cut the fabric using a razor knife. When I cut it with a hot knife, it cut neatly, sealed, and unraveling has not been an issue. If I didn't have an electric hot knife, I would try heating an old knife blade with a propane torch and cutting. Rustoleum leak seal is new to me. I'll file that away for future possibilities.

Thanks for the comment.

Herrick Kimball said...

vdeal—

Clothespins are a bit tedious but they have worked very well for me. Seems like there must be a better, cheaper, more durable, and/or easier approach. Let me know if you figure that out.

Yes, I'm chomping at the bit too.

But I wrote that once here years ago and a reader informed me that it's not "chomping" at the bit. It's "champing" at the bit. I looked it up. They were right. But nobody says "Champing at the bit." :-)

Herrick Kimball said...

Everett—
Hmmmmmm. I'm going to see if I can find some cheap big binder clips and give them a try this year.

I'm also going to start upgrading to 3/4" metal stakes instead of wood. I'm persuaded that the 30" bed with 18" walkways, and tight border strings (for attaching plastic) is the ideal dimension and system for my garden. The bed layout will stay that way for as long as I'm gardening here. If I leave, I'll literally "pull up stakes" and start my new garden beds with them.

Solarization should help with the potato pathogens. I am also planning to plant my potatoes on new land this year. It's hard for me to get good rotation in a fixed garden that has been in use for nearly 30 years. I hope to be posting an essay soon about how I used the bed and fabric to help grow potatoes last year.

Everett R Littlefield said...

Hi Herrick I was going to ask one more question yesterday before I left but forgot it! It is," When do you think the sun would be hot enough up here in our neck of the woods to start trying the solarization process"?

I just folded up all the black plastic I had covering the floor of my HT since fall. It never got really cold long enough to even kill the weeds in the outside gardens this year! Oh well. Got the last of the seeds and plants ordered. Also took about 50 pin oak acorns out of the freezer and put in the fridge for about 4-6 weeks. Then it is into big pots they go till they germinate. Got 36 like that last year and by fall they were all about three feet high. Going to use some of the new ones and sell the rest! Amazing what all these rich folks will pay for something raised and cultivated here on BI!

Unknown said...

I was convinced to buy 900 feet of the three foot wide woven plastic that you had recommended in previous posts. I am taking a different approach to the clothespin method of clamping the plastic to the string. I am folding the sides of the plastic sheet around the poly baler twine and pinning it with straight pins and then running the assembly through the wife's sewing machine using 4# mono filament fish line for thread. The intent is to hem the plastic without catching the poly twine in the thread. It looks like it will work! I am leaving plenty of poly twine sticking out the ends for fastening to the stakes.

I am a beginner at the sewing machine so there was a little cussing at first, but I am just about to the point where I can run a 25 foot stretch without breaking my thread. I did buy 6# line as well and haven't tried it yet because the 4# line seemed to be working well enough.

I chucked up a 3/4 inch bolt 3" long in the lathe and turned down a piece .675 inches in diameter and about 1-1/2 inches long and parted it off. I then drilled a 13/64 hole from end-to-end. The rod is a tight press fit through the reel of 4# mono filament fish line. The wife's sewing machine has two spindles for holding thread and I was able to unscrew one of them to get enough clearance to hold the fish line spool.

This will be a big sewing project and I am hoping to make enough beds to cover the garden. I will probably not do the paths this year as they can be cleaned off with my Whizbang Wheel Hoe easily enough.

Sincerely:

RonC

James Johnson said...

Elizabeth L. Johnson said,
Excellent post, this solarization! Can't wait to try this in one of my large gardens which is thickly covered with weeds, like a carpet, and it is only mid-March!!! When I think of all the many, and hot hours I have spent weeding!! You mentioned that you do not disturb the soil afterwards. Is that because it will only bring up more viable weed seeds? How then would you fertilize, if needed? Thanks!

Herrick Kimball said...

Elizabeth,

Yes, disturbing the soil would bring up viable weed seeds. I cultivated and fertilized the soil before covering with the clear plastic.

Everett R Littlefield said...

Hi Herrick, Back to this site again to report on my attempt at solarization. I only tried it alone both sides of my high tunnel. From the baseboard inward about one foot to kill the weeds in my walkway there. Well all I did was manage to make nice little "high tunnel hot houses" for the weeds to grow huge and push up the plastic and let them escape into the high tunnel! They didn't get watered except for what ever rain was able to seep under the outside edges of the baseboard. Guess I'll just go back to the lack plastic but of a higher strength/thickness. Good times man! BEST, Everett