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Will the oxalis (weed) invade my raised bed?

I just moved into a house with a very small (about 100 sq ft) lawn. Well, it used to be a lawn, but now it's an oxalis pes caprae patch. We weren't interested in keeping the lawn anyway - my plan was to put in a raised bed (probably 4' x 8' x 1') for a vegetable garden and put in some sort of easy low-maintenance ground cover on the rest. Given the oxalis problem, the ground cover is going to be cardboard covered in wood chips, which is fine, since realistically the dogs will use this area as their toilet.

For those of you elsewhere in the country, you might think of "oxalis" as a pretty ornamental flower, but those of you in coastal California know about the scourge that is oxalis pes caprae. I have found plenty of advice about how to get rid of it (e.g., "cover in 6 inches of concrete" and "move"). Hopefully I will live in the this house long enough for my hard work eradicating the oxalis to pay off!

My question is whether I have to abandon my plan for the raised bed for vegetables, until I get a grip on the oxalis. Since I won't be able to get rid of all the bulbs, will the oxalis just grow up through the bed? Or will they be buried too deep to sprout? Do I need to line the bottom of the bed? Is cardboard good enough?

This is my first vegetable garden, so I am feeling pretty clueless, though I have Pam Peirce and Mel Bartholomew on my shelf to help. Thank you!

Super Green Thumb
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Joined: Tue May 06, 2008 7:02 pm
Location: El Cerrito, CA

Here is your answer, and maybe more info than you were looking for. Somewhere along the line, I'll mention oxalis.

The good news! :) My first raised bed--the one *I* made with the salvaged (FreeCycle) concrete blocks and filled with the various composts and vermiculite and (heaven help us) peat--was approx. 8" deep. I just didn't believe Mel's statement that 6" would do the trick, even if I allowed for the rotting away of the newspapers at the bottom of the raised bed.

I was right.

Don't believe the man, at least not in the Bay Area, whose soil is underlain, at a very shallow depth, by adobe clay. Maybe in most areas of the world this is not the case, and plants can cast their roots further down, but 6" in a raised bed + a few inches, possibly a foot, more, won't keep carrots, cereal crops (yes, I grew wheat in 2008/09), or other plants with extensive root systems happy.

Make those raised beds 12 inches deep. Ten inches minimum.

So now Bed #1 is happy. More or less. Many valerian seedlings come up, courtesy of my compost, but almost nothing else, unless the birds or the wind have brought seeds there. And Bed #1 was "planted" over foxtail, mallow, blackberry, and oxalis. There is occasional breakthrough of blackberry. But the blackberry has only made its way up the center of one of the cinderblocks. Briefly. :twisted:

Then, even though I got additional materials through FreeCycle for a "potato tower" (separate topic; a search will bring it up for you) and an additional veggie bed, DH felt--because he actually used his Makita to join said materials together, no doubt--*entitled* to fill those raised beds any old way. This, when he hadn't read anything, dug around in the dirt, or *heaven forfend* listened to me when it came time to fill Beds #2, #3, and, many months later, #4. "No native soil," I said. "Too many weed seeds, and zillions of oxalis bulbs. We can build up these beds with our compost." Because they were in the one small area where, 10 years ago, we had improved the soil and that infamous clay had been broken apart for good. Shallow planting soil, gradually built up, would be fine.

Thus it came to pass that, on the day I knew that we needed to turn the compost to get something into those beds, I looked at them and they were full?! :shock:

OK. That was weird. This was at the depth of my under/unemployment saga, and I knew that we didn't have $ for anything but the basics. That's fine; I can manage. It's how I grew up, anyway (and we didn't have great stuff like FreeCycle then!). But I wondered--did he go out and BUY all this potting soil??? :?

Then I walked over to the two new beds (Beds #2 and #3) and stuck my hand into the soil to check it out.

Oh, no!!! :!: ...native soil! Absolutely FULL of oxalis bulbs!

And they are still a nightmare, even though the potato tower pretty much discouraged most of the oxalis in Bed #2. It's been over a year since we harvested the famous potatoes. We grew some leafy greens and some root veggies in Bed #2 last year, which means...the oxalis bulbs got sunlight. :evil: And I've been pulling them out. Again.

The only thing that saves the situation is that, when you pull oxalis out of a raised bed, you get the WHOLE root. I've gotten some that are 9 or so inches long below the soil surface, which makes for a pretty l-o-n-g plant. :shock:

Bed #3 has had sunlight all along. You know what that means. :( But I'm making progress.

By the time we made Bed #4 (I made sure to hold the Makita part of the time on Bed #4 :twisted:), I had an anti-oxalis/weed plan. Part of my plan worked.

Close planting of leafy greens deprived the oxalis of sunlight. So, in half of the bed, oxalis was severely set back. But, in the other half, I wanted to try tomatoes and a couple of other veggies that come up out of the soil rather than staying so close to it.

On the other hand, be happy you're not dealing with the ones I've already removed (by hand) because they generate spines, thorns, burrs, etc. or are otherwise harmful/toxic to neighborhood cats or my dogs:

--redstem filaree
--yellow star thistle
--wild onion

Oxalis isn't harmful to dogs, should they take an interest in it. Mine seem to prefer young foxtail grass, but they never eat enough of it to prevent later foxtails. I've been fighting that one for years....

Let me know your plans for filling your raised beds. If you'll be using your own compost, etc. *and* 10" or so of depth, you'll be seeing very few oxalis in those beds.

But if you use native soil... :x is how you'll feel. Just so ya know... :D

Welcome to The Helpful Gardener, and happy gardening. Where in Zone 17 are you? It's a pretty long, skinny zone on the coast.

Cynthia H.
Sunset Zone 17, USDA Zone 9

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:roll: I have oxalis everywhere but have given up on doing anything except trying to pull it out, it grows everywhere here.

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Thanks, Cynthia. Bottom line - You think I'll be OK with a 12" bed, with cardboard in the bottom? I wouldn't dream of trying to use the oxalis-infested soil from my yard. It's a shame because I think the soil is probably pretty nice - the clay layer is a bit deeper, I think. The soil is full of earthworms.

I haven't even started learning everything I need to know about soil. I have only just begun to assess the feasibility of the whole gardening project. I don't think I would trust any free soil for my bed, so I will have to shell out some money. I saw on another post that you recommended American Soil and Stone in Richmond, so that's likely to be where I go. (I am just a few miles south of you.) I hope it's not going to cost too much.

I'm glad my husband wouldn't dream of doing such a thing! :wink: He knows the garden is my project. :)

I am not able to get much of the oxalis root out, even though I have been pulling them right after the rain. I think it's because I'm not able to pull them through the layer of sod that is covering the area. My plan is to pull up the sod entirely - it comes up pretty easily - so we'll get oxalis and what's left of the grass in one fell swoop. I can see a lot of bulbs (along with happy earthworms) just under the sod layer.

Butterfly, from what I have read about oxalis pes caprae, there isn't really a whole lot more you can do. You just keep ripping them out every year until they give up, and a layer of mulch can help. You can use herbicides, but I'm not interested in going down that road. Here are some useful articles that talk about eradicating oxalis, for anyone who is interested:
[url=]Stopping oxalis is no small task[/url]
[url=]Nipping oxalis in the bulbs is key to control[/url]
[url=]Act now to stop the spread of oxalis[/url]

Super Green Thumb
Posts: 7500
Joined: Tue May 06, 2008 7:02 pm
Location: El Cerrito, CA

Great links!

And, yes, 12" with cardboard will be great. Bed #1--the *good* bed--was only 8" and had newspaper.

You'll have more insurance than that, so I feel secure in saying that you should only see a scattered one or two here and there (if squirrels or such transplant them).


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FWIW - Plants for A Future database lists the flowers and leaves as edible in small quantities (be sure to note the warning) :

I've used the Oxalis incarnata (Wood sorrel) in salads and lemonade/ice tea as garnishes, and they're great hit when the leaves are separated into little hearts. The yellow flowers add sprinkling of color (and flavor) to salad.

If you can't beat them, EAT THEM! :()

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I think the key words are "in small quantities" - if I had small quantities of oxalis, I wouldn't be writing about it. :)

Without going into a whole "what is a weed" debate, it's not really such an evil plant. It's pretty and edible. Its only sin is being too well adapted to this environment. Despite the fact that I have declared war on oxalis, I have not worked up any hatred for the plant. I just don't want it to be the only thing growing in my garden. Total annihilation is my only option!

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