I find weeding the garden can be quite therapeutic, getting down on your hands and knees amongst the plants you can forget about life’s troubles and just concentrate on pulling up those pesky weeds while you burn some calories! If you are vigilant and ensure that the weeds are removed before they can have a chance to flower and spread their seeds then most weeds will not return either!
One weed that is not so easy to get rid of is my arch enemy oxalis pes-caprae, also known as soursob and sour grass. This weed is not going to go away if you pull up the plant because the bulbs are still left in the ground and will re-emerge at the next opportunity!
Oxalis Weeds Growing Through My Salvia Plant!
In the past I have been successful in wiping out the oxalis when it is in an open area by spraying it with a glyphosate based product, like Roundup. However, it is not possible to spray it when it is in and around the plants in a garden bed. I’m too scared I’ll kill my other plants!
So I have been looking online for information that will help me in my quest to wipe out (or at least minimise) the oxalis in my garden. The following links have given me valuable information to help me control the oxalis weeds in my garden.
Removing Oxalis Weeds – A Multistep Approach
To get the maximum reduction of oxalis in the garden you need to use a variety of techniques and be prepared to keep treating the area until you have the weeds under control.
Firstly it is possible to remove the weeds by hand but it is essential that you make every effort to remove as many of the bulbs as possible. The soil can be sifted to ensure all of the bulbs are removed but this can be very tedious. Personally I have not found the results of sifting to equal the effort required.
Also be careful when disposing of oxalis weeds, you don’t want to spread them to another location. Where possible put them in a plastic bag and leave them in the sun to ensure that the plant and the bulbs have been killed.
Oxalis can be eliminated from garden beds by removing several inches of the topsoil which ensures that all of the bulbs are removed. This method could provide a quick solution to the problem but might be costly if a large area of topsoil is involved.
The oxalis weeds that have come up through my mulch this year!
Putting down a thick layer of newspaper followed by garden mulch has also been suggested as a useful way to control oxalis weeds. I have only recently begun doing this and I have had some success.
The use of chemicals such as glyphosate or metsulfuron methyl are also suggested as potential solutions but care must be taken when using any chemical not to harm other plants, animals or people. As I mentioned earlier I have had some success using glyphosate but it is not possible to use it on the weeds that are growing right in and around garden plants.
Some great links that discuss all of these methods are:
Royal Horticultural Society website: Oxalis
Best Time to Spray Oxalis Weeds
Each of the above links stress that it is important to spray oxalis at the right time to maximise the effect of the chemical. Just prior to flowering is the best time to spray oxalis weeds because the older bulbs have put all of their energy into the flowers and new bulbs have not had a chance to grow yet.
Oxalis Weeds with Flowers that are Just About to Open!
I was able to find a very old study that looked at glyphosate control of oxalis and it has a great illustration showing the best time to spray oxalis weeds. Although the study was focused on reducing oxalis in cereal crops it still provides great information on killing oxalis in any garden.
This study suggested that oxalis should be sprayed with glyphosate at either growth stages 5 or 6 which are shown in the illustration (below).
Taken from PDF: Glyphosate for control of soursob in winter cereal systems in southern Australia
Source Council of Australasian Weed Societies Inc. website
The full study can be found here:
Suppressing Oxalis Weeds with Fertiliser
One method of suppressing oxalis that I had not thought of before looking online is using fertiliser. According to the link below you can apply an appropriate fertiliser to your plants over the summer months while the oxalis is dormant. When the oxalis begins to grow in autumn they will get too much fertiliser and they will die. Just be careful not to fertilise if you have native Australian plants in your garden.
Gardening Australia website: Fact Sheet: Garden Weeds
Suppressing Oxalis Weeds using Soil pH
Adjusting the Soil pH Might Deter the Oxalis
It has also been suggested online that correcting soil pH might help to suppress oxalis weeds. In the gardening forum link below, one contributor suggests that oxalis prefers a soil pH of around 5. Testing soil pH is something that should be done occasionally so it can be adjusted to suit your plants requirements. If your soil pH is low it would be possible to check the pH that your plants require and then raise the pH accordingly. As many other plants require the soil pH to be closer to 7 (neutral) it might be possible to raise the pH of the soil and deter the oxalis.
Geelong Organic Gardeners Inc. website: Winter weeds: thoughts on tactics
I have learnt a lot about controlling oxalis from the links above. I already knew that it was very hard to remove all the bulbs but it is great to find so many other methods that I can try. I think that I will be using a combination of these methods in the future. I will also have to be persistent and keep trying these methods for a few years.
Hi, I'm Kaylene, and I'm a keen gardener,budding baker and wannabe DIYer!
Try spraying with Aerogard, this does not kill your plants but kills the oxalis
Thanks for the suggesting Linda, I have just sprayed a small patch to see if it will work!
What is areogard ? Web says it is a insect spray.
Hi Mike, Areogard is a spray on personal insect repellent commonly used here in Australia (active ingredient is Picaridin). You spray it on exposed skin to repel biting insects. I have found that it works best on the purple oxalis – see more recent post here: https://thelinkssite.com/2016/02/05/controlling-purple-oxalis-weed/
I hope that helps!
G’day Kaylene, how did the Aerogard go for you? It’s that time of year again for oxalis and I’ll give this a go if you’ve had some success. Thanks in advance. Dave.
Hi Dave, I did have some success with the Aerogard, in particular the purple leaf oxalis that is more of a creeping variety.
I found that the soursob oxalis (winter one that I think you are referring to) didn’t like it much either. The leaves burnt off a bit but because I have a lot of it in my garden I would have needed a few cans of Aerogard to kill it all! The little patches of purple oxalis are a bit easier to kill with Aerogard but even with that one you have to reapply it if you see it beginning to regrow.
Overall I think that the Aerogard does work but you have to be vigilant and reapply if necessary. I haven’t used it much on the soursob because the patches of it in my garden are too big.
See this link for a more recent post discussing the use of Aerogard: https://thelinkssite.com/2016/02/05/controlling-purple-oxalis-weed/
I hope you have some luck controlling the oxalis weeds in your garden!
Hi Kaylene,
Just wanted to say thanks for your post, it’s full of great information and can’t wait to start implementing some of the suggestions you’ve shared to rid my yard of the awful soursob.
You’re welcome Sarai. I hope you do have some luck getting rid of the horrible stuff, I’m still working on clearing it from my garden. Unfortunately I think it can take some time depending on how badly it has taken hold!
Thanks Kaylene, sounds and looks very promising. I heard about this method many years ago on ABC radio in Melbourne during the Saturday morning gardening program with Kevin Heinze. As you have noted he also said repeated applications are necessary for best results. Cheers, Dave.
I have Sour Grass (Oxalis w/yellow flowers) in my yard and I want to kill other weeds/grass, but not the oxalis. Any ideas?
Hi Patrick, depending on the number of other weeds you have, you could try pouring some boiling water on the weeds you want to kill – they don’t generally like that. Otherwise I would suggest pulling out the other weeds before they get a chance to seed, that way next year the oxalis would come up but the others might not. However you choose to kill the other weeds I wouldn’t be to worried about the oxalis. In my experience it is very hard to kill, even if you kill the growth for this year the bulbs will still be okay under the ground and they will most likely come up again next year. I hope that helps you a bit!
where do you get the seed for oxalis sour grass
I’m sorry Sal but oxalis (sour grass) is a weed in my garden so I have never looked into where to get the seeds. Perhaps you could try an online plant seller in your local area. There are many companies that sell plant seeds online.
Does anyone know how to make the conditions less favourable for oxalis?
I have both the purple and green, but the green is much harder to set back because of all the little seeds. Have spent hundreds of dollars trying to eliminate it with hired help….it is outrageously hard to even set it back.
Hi Josie, you could try putting out plenty of fertilizer around you plants during spring and summer. The oxalis doesn’t like the extra fertilizer when it come up in autumn/winter. You’ll need to do this for several years to get completely get rid of the oxalis. Unfortunately oxalis is one of the worst weeds to get in the garden, once you have it in your garden it is very hard to get rid of!
It is a pest that never leaves. I too have spent thousands for its eradication without any concrete results.
I have tried all of the above..with out any good results. Seems i have to live with it and I now mow the garden with it there.
We call it Buck weed or Batakneur in our local lingo
Sadly I think you’re right, once this weed gets established in a garden it is almost impossible to completely get rid of it. I just do as much as I can to try to minimise its presence!
Hey Kaylene,
Great post! I found it very helpful a lot. I’d like to try something similar with this at home soon. Thanks for sharing.
Cheers,
Oliver
Hi there… another possibility. Oxalis is a herb and can be used for culinary purposes. It grows wild here a the Cape and has been used for millennia. Great nutrients but a little too much kidney stone causing oxalic acid means that it should be eaten in moderation. Sprinkled on soups, used to garnish cakes, added to sandwiches and such things, for the piquant sourness, and the pretty leaves and edible flowers.
Thanks for the suggestion Caroline, I had never thought about eating it!
ha ha… I guess eating it is one of my first solutions to a problem (ahem) thats me, but this time, backed up by long tradition
I’m glad you suggested it, I’ll have to give it a try! May as well find an upside to having it in the garden!
I’m in London, UK, and have chickens that love eating oxalis. My garden has a ridiculous amount of oxalis – and I like it as it’s pretty and doesn’t really do too much harm. I don’t let the chooks have too much as I’m sure an excess of oxalic acid is not the best of diet plans.
Would a weed-whacker help? A heat wand? I use mine when the sorrel gets way out of hand.
On the plus side, it’s a very pretty plant and provides good ground cover. I can think of many plants I like less.
I wish I had some chickens to eat some of my oxalis 😉 Good suggestion of a heat wand, I will give that a try!
Re sour sobs – Several years ago I read that each sour sob bulb will only produce one plant, and pulling the plant will kill the bulb. Ideally, this should be done before it has produced baby bulbs. I decided to test this theory by waging all out war in one area of my garden. I pulled continuously, clearing the area at least 6 times, during the plants growing season. The following year there didn’t appear to be much difference, but the year after that, the sour sob population was less than half what it had been. The area is now virtually sour sob free.
I’ll have to try doing that in my garden Shari. I have had some success battling it but it seems to be one weed that you have to keep at in order to get rid of it! I’m glad to hear that you had great results, you’ve inspired me to get stuck into my sour sob problem again!
My beautiful lawn is covered in oxalis which I’ve found very difficult to remove. The grass is buffalo so quite hardy but I can dig deep to get the bulbs out.
Any suggestions?
Hi Mariela, I have never had to treat my lawn for oxalis but I have read that you can use a broadleaf herbicide to treat oxalis in lawns. You just have to make sure that you get one that is specifically designed for buffalo. A garden centre should be able to help you with this. I have also seen that you can get broadleaf herbicides for buffalo at Bunnings. It’s not ideal to have to resort to chemical sprays, but when dealing with a problem weed like oxalis this might be your only option! I hope that helps, please feel free to let me know how you get on!
I have the same problem with it in my buffalo lawn
I have been out there the last several days pulling it out. Reaching through the lawn to pull as much of the root out as will come
I dug the weed out of a new garden bed, bulbs and all. Got rid of a huge bulk of it
I hope you are able to rid your lawn of it Trish, you must be sick of it after toiling for several days! Great that you have been able to dig out bulbs and all in the garden bed, the more bulbs you can remove the better!
Here is an article I had copied many years ago which I have found useful
https://www.cal-ipc.org/newsletter/caleppc_news3067-pdf/
It mentions lateral growth which I believe you did not.
The picture you reproduced is especially welcome!! Thanks for a great article.
Hi Patricia, I haven’t noticed this yellow buttercup oxalis having any lateral growth in my garden. Just as well, the tiny bulbs it produces cause enough trouble! I have noticed lateral growth in the creeping purple oxalis though. I shared some information about it in another post here: https://thelinkssite.com/controlling-purple-oxalis-weed/
It is a bit of a pest to get rid of too, and it definitely has lots of lateral growth.
Thanks for sharing your article it looks interesting. I will put aside some time to read it thoroughly as it is oxalis season in my garden at the moment!!
I’m just embarking on this war. I found your article to be excellent. I’d like to add this concept – timing!
This paragraph strikes me as being key to any success:
“Soursob (Oxalis pes-caprae) is difficult to eradicate unless control methods are well timed and persistent over several years. The plant must be attacked at a critical stage in its life cycle called the bulb exhaustion stage. This is when the food material of the bulb is exhausted and any new bulbils are not sufficiently developed to survive. Unfortunately this stage cannot be accurately determined by looking at the aerial growth, only by digging up plants and inspecting the bulbs. The bulb exhaustion stage is just at, or just prior, to flowering. Unfortunately, not all plants in an infestation will be at the same stage at the same time. Any control method, be it cultivation or chemical, should be aimed at this critical stage (Muyt 2001; Parsons & Cuthbertson 2001; Brown & Brooks 2002).”
It’s from the ‘How To Manage It’ section of this page: https://weeds.org.au/profiles/soursob-bermuda-buttercup-buttercup-oxalis-cape-cowslip-geelsuring-oxalis-sorrel-sourgrass-yellow-flowered-oxalis-yellow-sorrel/#prosection4
We can try to aim our efforts at the “bulb exhaustion stage”.
Good luck to us all in our ongoing war against soursobs!
Vija (Australia)
Thanks for the information Vija, any hints around controlling this pest of a plant are greatfully accepted! That website looks like another great reference. I will check it out and add it to my article. The more information that is out there the better!