How can I use this weed?

I have a strong belief that weeds are very important in the garden as they are able to forage the soil for nutrients, and the roots of weeds create little channels for worms and the roots of other plants. I'm also a big fan of eating weeds.

However, I have one weed in my garden that is getting the better of me. Oh, did I say 'in' the garden, I should say completely covering the garden!!

In one month, despite repeated experiments to control it's growth, oxalis pes-caprae (aka soursob, sour grass, wood sorrel etc) has taken over my entire garden, and seedlings have been swamped.

It forms a dense covering, preventing light from getting to the ground.
It grows faster than anything else, getting to full height in a few weeks.
It tastes horrible (I've tried it raw and in soup and I've decided it's not my thing. I also tried dehydrating some and adding it to soup; it tasted better than fresh soursob, but worse than soup without it)
When pulled up it leaves multiple bulbs in the soil that each turn into a new plant.
It regrows from root pieces and the roots form a very complicated underground network which make them impossible to fully remove.

So on the one hand this is a good weed for building up a very fertile, worm-rich soil. On the other hand I would like to grow other things in addition to soursob.

This is what I've tried doing with it so far:
- giving it a haircut and leaving the leaves as a mulch - this didn't work, it was time intensive, sometimes I cut seedlings in half accidentally, and the soursob regrew in a matter of days
- pulling it up and using it as a mulch - this didn't work, the plants stayed sappy for as long as I left it there (eg, after a month the mulch was still sappy and green despite it being pulled out and exposed) and it prevented any vegetable seeds from germinating.
- leaving it be - well it grew bigger than the plants and took over everything
- throwing mulch all over it - this prevents the seeds I sowed from sprouting, and the soursob gets through anyway. As an example I planted tulip bulbs in a 40cm pot and placed this pot over 30-40cm of fresh mulch. Within two weeks the pot was full of soursob.

My current strategy is to pull it out and then throw it in a pile in the backyard to work out what to do with. The pile is getting as large as a hugel bed! My seedlings then have a head start of about a week before I have a new soursob plant in it's place. This strategy is working the best in terms of other seeds being able to at least sprout, but it's so labour intensive. This plant is reportedly one of the world's most difficult to control weeds.

So, now I have this growing pile and I do not for the life of me know what to do with it. Most people poison this plant or at the very least throw it out but my recycling ethic will let me do no such thing.

Should I turn it into sludge in a vat of water? Bury it? Compost it somehow? A humongous bokashi bucket? Dehydrate it and then sprinkle it back on the plant beds, cackling with glee?

Help!

do you know anyone with ducks? ducks love that plant, I havn't tried it on my rabbits. It will survive 2 year's under mulch, it's funny i tried to grow it and it never took off, i mulch the area heavily then planted something else and now it's finally getting to the point I can harvest it again. If you can link up with poultry, now your harvesting a yield by weeding rather than slaving to a menace. It's how i feel about slugs.

There was one mulch that worked - used woodchip kitty litter tossed onto a pile in the backyard under an ornamental tree. The soursob hated that.

I don't know anyone with any kind of fowl, but I've been planning to get chickens of my own. Do you think they'd eat it?

To kill the area that still has plants in it, you could do soil solarization. But that takes many months, if not a year, and you won't be able to grow anything there until it's finished. But if you're willing to be that patient, you'll be able to grow stuff in that spot, and pull up any of these weeds as soon as you see any sign of them. Maybe you'll be able to stay ahead of them at that point. As for the ones you pulled, you could make hot compost if you don't have any ducks to feed it to.

A controlled burn of your pile would give you a nice supply of ashes.
What minerals they have pulled from your soil will remain in the ashes.

It's taken my whole garden and I have earthworms etc! Sunbaking the soil under clear plastic sounds terrifying!!! Or are you thinking of sun baking just one spot per year? In any case I'm not sure that it's feasible when the whole garden is affected.

One thing I was thinking of doing is instead of mulching everything as I do currently, I could make huge piles of mulch in one spot every time i get my mulch delivered (I have a neighbor who brings many bags of alfalfa hay spoiled with guinea pig droppings). Perhaps that way by the time the soursob got through to the top the bulb would be pretty exhausted. Then once that spot is all weed free make another huge pile.

I messed up in one spot in the garden though. I made a big pile of leaf litter and twigs and then spotted this old plastic pot under a tree with nothing in it but soil. I poured the soil out and the entire bottom half of the pot was soursob bulbs. Eeeek! I cleaned up as many as I could but I suspect many fell in the leaf litter.

I would simply change the soil profile. It just really likes your soil and your environment. Chances are it may not like something else.

Also encourage things that like to eat it

And as always every problem is a solution in hiding.

Jordan what do you mean change the soil profile? If I look out at my street everyone's entire garden is smothered by this one weed. My soil is very healthy, teeming with worms, fungus and lots of bugs. But the one plant is everywhere. Nothing that i have available to me likes to eat it. I know it is a serious crop pest too, it takes out a whole field and the sheep eat it and get poisoned.

I'm not specifically trying to eradicate it per se, as that goal would be far too stressful to try to complete. More that I need some ideas for what to use it for.

John Polk, I've never burned anything before. I'm in a small residential street with neighbors close by, but it's a good idea, it would definitely reduce the growing pile. I'm not sure how to burn it though, it stays sappy and wet, it might put out the fire! Maybe I need to invite friends over for a BBQ and then put the weeds on the hot coals afterwards, lol. Mmmmm..... BBQ soursob.

Nick mentioned hot compost, does that mean leaving it in a pile and adding fresh manure?

they make a stand up bulb planter, like a cone shaped shovel.

You may be able to punch down deep enough with it to pull up the bulbs.

If it is muciligous, you can try it for mosquito repellent, sun burn releif.

take it back over to the freind that is bringing you leftovers, and see if her animals like it!

She poisoned all of her's. It kills her guinea pigs.

Not mucilaginous either, although it likes to form a guild with dwarf marshmallow which is mucilaginous. The marshmallow doesn't bother me.

If I put my pile of weeds in a tank with some bricks on top and poured liquid on it, do you think that would make a fertilizing tea?

I've never tried it before but you could try spraying the sorrel with veggie oil. I've used used cooking oil in a spray bottle to kill weeds in the driveway but not in the garden. Just be sure to keep it off your edibles. The oil smothers the leaves and concentrates heat from the sun thus burning the plant over the course of a week or so.

They're in the shady as well as sunny spots, but I'll give that a go in a sunny area and see what effect it has. If it works then I could at least get rid of some of them without pulling them out. Cheers!

Peta, are you in Australia? I ask as I've only heard Aussies complain about soursob.
It would be great if you added some geographical info https://permies.com/t/7677/tinkering-site/Please-add-your-location-zone
I've got standard oxalis, but not in the veggie garden, and I've decided not to fight it anymore.
If you're not able to heavily mulch entire areas for a couple of years, or get the feathered work-gang in, I think it's a matter of trying to work around it, because you won't win!
I don't know how much they compete with other plants. My version isn't that tall, but it's pretty prolific. I think I got a bit of an embattled 'Leila vs the oxalis' thing. I would've come off second-best
I try and maintain very fertile soil, very thick mulch and do as little digging as possible. The corms will sit dormant for years underground, but if they surface, they'll grow immediately.
If using a barrel, be aware that the corms take ages to 'drown', so make sure they've turned to mush before doing anything else with them..I think the plants, minus corms can't survive.

I wasn't sure what plant you were describing, so I looked it up. Lo and behold, that's what we used to call Bermuda Buttercup when I lived in So. Calif. In Israel, it is also a common weed, called Wood Sorrel there. It is a transplant from So Africa, and loves a warm, arid climate.

They have beautiful flowers, but are indeed difficult to get rid of.

The weed propagates largely through its underground bulbs and this is one reason why it is so difficult to eradicate, as pulling up the stems leaves the bulbs behind. Soil in which the plant has grown is generally filled with small bulbs.

Yep, Australia. I don't think our soursob is common in Wellington; I've been there a few times and have never seen it. I think your oxalis comes up in summer whereas ours comes up in winter?

I have done some experiments with just letting the weed do whatever as there is far too much for me to pull and i never intended to weed my garden, just harvest and plant things and mulch, but I have to admit the desired seeds and seedlings have only established themselves in the places where I pulled the soursob. By the time the new soursob plant grows back if the seedling is a little taller it won't have to stretch so far and then become straggly and fall over. Currently the small plants can't support themselves. Beetroot or silverbeet for example, will send it's shoot up to try to get some light, and then will fall over as soon as there is any disturbance as it's so skinny and weak. Planted seedlings don't do any better unless I protect them somehow. After some expwrimentation I've taken to pulling the soursob then planting seedlings in brown paper bags with weed-free soil added and then placed where the soursob was and mulched. This works well, so I could just plant all my garden this way and let the soursob do it's thing, by the time the soursob has penetrated the bags my seedlings are tall enough. But it is time consuming and i don't have any more bought seedlings, I'm keen to experiment with broadcasting a polyculture of seeds to create a seed bank in my soil.

I think in the long term I'll have to turn the whole garden into perennials. The soursobs are all through the perennials too but it doesn't matter so much as they've already grown tall enough to get light.

That's the one!

So obviously I don't want to pull it up due to all those bulbs, but where I have left it it has spread everywhere anyway. Getting plants back is no worse than already having a plant there, if you know what I mean. If I pull them it slows them down and then maybe the mulch will work over time. If I look over both my neighbors fences (who are tenants and do not garden for food) their entire 'lawn' is in fact this weed. It seems to be well established, this is my first year here.

A picture is worth a thousand words right?

Sorry, I'll try again... the pics with spaces in the name didn't work

This picture is where I did weed and it worked, not nearly so interesting:

OK, lets try again without using the Attachments section this time...

This area I weeded one week ago, the coriander has been able to sprout but the soil was tough here next to the pavement and the bulbs grew back almost instantly



This area I tried to mulch with thick newspaper, the beet made it but the sour sob is coming in from the sides:



In this picture the tiny little babies are cowering in fear as their 'safely' heavily mulched haven suddenly sprouts soursob!

This area I haven't weeded yet, actually I lie, I tried decapitating these:



The area at the front I planted in paper bags, the area at the back I planted into thick mulch (I planted a lot more in the back area but most of the babies died when the soursob came in):



I planted daikon, radish and carrot here, 10cm apart. The soursob swamped the area and only one daikon made it; it sprouted before the soursob grew this big:

In the backyard it is breaking up my hard clay so does have some use at least

Peta, Hot composting can be done with or without manure. If you get the pile the right size (about 1.5 meters cubed) and the right mix of greens and browns, and the right moisture content and the right aeration (oxygen), thermophile bacteria take off and rapid decomposition occurs. I've measure as high as 160 degrees F in the middle of some of my hot compost piles. The high temp kills a lot of seeds and disease organisms. Black finished compost can be made in as little as 2 weeks, but to do that, it has to be turned every few days to inject more oxygen into the microherd.

As for soil solarization, your earthworms will go deeper to avoid the high temperature. All your soil life will return when you resume gardening in that area. Your weed problem is one of the worst I've ever seen. Another option would be very deep mulch - half a meter or more on top of cardboard and wait at least 6 months.

In the backyard I had some old carpet that I hadn't thrown away yet. I lifted it and low and behold there was no soursob there. Only white exposed roots where it had tried. So I think that mulching will get it in the end. I'm thinking that instead of mulching my whole garden small layers at a time to feed [the garden], I'm going to add all my mulch into one pile until it reaches a good height, and then plant into it and start a new pile somewhere else.

I like your plan. Maybe you can rent some ducks for the rest of it.

I would be reluctant to feed it to any form of livestock, as per Wikipedia:

From Wikipedia:

Oxalic acid is toxic in large quantities, a concern in regions such as southern Australia where
Oxalis pes-caprae grows invasively in enormous quantities and in high densities

Oxalis pes-caprae certainly can cause dramatic stock losses. For example, when hungry stock,
such as sheep released just after being shorn, are let out to graze in a lush growth of
Oxalis pes-caprae, they may gorge on the plant, with fatal results, as has been found in South Australia at least.

The plant has been found to be nutritious, but too acidic to be good fodder, largely being left
untouched by grazing stock. When stock do consume large quantities, the effects typically involve death in
several weeks with symptoms suggesting chronic oxalate poisoning, including tetany or sudden death with extensive
renal damage. Such damage suggests the twofold effect of calcium immobilisation (the tetany) and the formation of
Calcium Oxalate Monohydrate raphides in the kidney tissue.

Yes, I read the same article, hence would never offer it to my friend's guinea pigs!

I'm not sure whether fowl are the same though, I was reading it is kept in check in south Africa by a native guinea fowl. Some people have found their chickens dig up and eat the bulbs, although others say their chickens avoid the soursob and eat anything but. Guess it depends on the chook.

you would think gophers or voles would love this, a horizontal buffet.

I would clear a small area of mulch and dump ashes on it, see if the alkalai helps or hurts it.

We don't have gophers or voles here!

Are you suggesting putting ashes down in a cleared area, or on top of the weeds?

One benefit I do have is that my most weed infested areas are producing the most perfect broccoli as the cabbage butterflies and aphids are missing them. I have never seed soursob eaten by an insect. I just can't plant any more baby broccoli in the space as the big sobs own the space now. The broccoli on the edges of the bed where they are not covered in soursob are looking very worse for wear, and I've told the poor buggers that they have to just pull through on their own because I won't be spraying them ith anything.

Shhh.... Don't tell them I plan to pull them before they set seed.

I'm thinking a couple of things. In the traditional annual garden beds, you could build raised beds. Cover the ground first with cardboard, thickly and well overlapped. This will exclude light that the oxalis needs to grow. Then build beds on top, with attention to excluding light. You can't ever dig into the level where the cardboard has been though.

You need to find out if the oxalis is seeding, and make sure that you weed before it seeds.

The other idea was in places like under that tree, plant an edible perennial garden. The weeding/mulching techniques will be more effective in a perennial bed than an annual.

I had bits of oxalis in my last garden but it never seemed to spread. I just left it alone. People used to say to me that I should get rid of it or it would spread everywhere. I wonder if heavy weeding makes it propagate faster eg exposing bulbs to light. Have you tried chop and drop and no dig?

Also, mentioned upthread was the idea that the soil suits oxalis very well in your area. Maybe that is a clue. Have you tested the pH? I'm guessing the soil is acidic, so making it less acidic might make the garden less attractive to the oxalis.

Over time I'll be raising all the beds. I moved into this property four months ago and put 30-50cm of spoiled alfalfa and guinea pig droppings over the entire front garden. Now that the soursob has come in I'll be raising the beds further to try to prevent it next year.

To try to save this season, I've hand-weeded the whole front garden, but it is rather devastating. It looks like a tribe of small elephants has been learning to tango on it. Not that I stepped on any of the larger plants, but when plants are being propped up by the weeds they don't grow strong enough roots, and a lot of my veggies have just fallen over. Other seedlings got damaged by all the pulling going on. I hate to do it, but it's the only way seeds are going to sprout. Some seeds already sprouted and I'm hoping the yellow leaves will turn green again soon and they'll grow. I'll try to pretty up the garden again with a tidy up so that I feel better about it.

Chop and drop definitely didn't work. The picture sprouting the healthiest crop of weeds was taken only a week after a 'haircut'.

Soursob is very well suited to all of SA, both the climate and the soil.

Hi Peta, probably a bit late for this reply, but I came across your site while researching oxalic acid poisoning in poultry. Several of mine are staggering and having trouble walking after eating quite a bit of it - so I wouldn't recommend feeding it to them. Also, gardening guru Malcolm Campbell has suggested fertilising where it grows, as it comes from poor sandy soils in South Africa, and doesn't like rich soils. I'm currently giving it a go. (I'm in S Aus). the other thing I've tried is carpet - that does work by smothering them, but you have to leave it there for at least a couple of years, so you lose growing space. Hope your raised beds have worked.

Would cooking it destroy the
poisons?
If so, perhaps a solar cooker or dehydrator would allow it to be used as mulch or feed.
Sour as it is, it seems like a natural for beverages.
Another spray to try might be agricultural vinager.

I live in Los Angeles and my yard has a lot of this stuff. The property I'm currently on has been abandoned for some time. I thought I should let it go a bit and help build soil, but after reading this it seems like an exception to that method. So no S.T.U.N. I wonder if anyone has had any luck using the sheet mulching method described in Gaya's Garden. It seems pretty full proof but life finds a way right? I am most interested in the hot mulch pile method. Would you just be slowly chasing it around the yard by moving piles here and there? I will try and make a bucket of compost tea with it. I certainly have enough to experiment with!

Brandon,

I have been in the Bay Area for almost a year, and when I moved here last August, I did not notice that much of it. Then when we had that two weeks of rain in December it was everywhere. I have heard from others in this area that it dies off in late spring, and does not come back until Fall. Have you noticed if it does the same on your property? I also noticed it loves the compacted clay areas in my yard. I was curious, and transplanted it in a shaded very compact clay area in my yard where nothing was growing. It is doing very well, and I am hoping that it will break up compaction.

J Argyle wrote:Brandon,

I have been in the Bay Area for almost a year, and when I moved here last August, I did not notice that much of it. Then when we had that two weeks of rain in December it was everywhere. I have heard from others in this area that it dies off in late spring, and does not come back until Fall. Have you noticed if it does the same on your property? I also noticed it loves the compacted clay areas in my yard. I was curious, and transplanted it in a shaded very compact clay area in my yard where nothing was growing. It is doing very well, and I am hoping that it will break up compaction.

Like other clovers, I assume this one works to put nitrogen back into the soil. and every year when it dies down (here in the Central Valley of California) there is bunch of bio mass added to the soil. I usually just transplant into the clover patch, mulch, and come back a little later and weed what popped back up. By Summer most of it is gone, and my heavy feeders are using up the beds with a little cilantro and greens. When I do pull mass clovers, my soil warms up and starts to harden up (mostly clay) so unless it's flowering it's probably fine to leave as is until you can plan to plant and mulch it. No sense in fighting it, try cardboard layers instead of newpapers and use more mulch! Don't feed it to animals in massive quantities, and yes, it does make a pretty good oxalis-ade.

P.S. I've also had success pulling massive quantities, reusing some old plastic bags and filling them with the clover and leaving them to dry/die for a year.

I believe that Wood Sorrel is not a nitrogen fixing plant. It looks like a clover, but is not in the Trifolium family