Oxalis is all around my garden. Spray products are effective for a short time but it always comes back. I laid weed mat covered with pea straw but it grew through. What else might work? Could sieving the soil get rid of them?
Oxalis is a bulbous weed which grows under the ground level so covering it doesn’t work. It is very problematic once it is in your garden as the bulbs multiply and spread easily. To get rid of oxalis chemically would affect the soil very badly and it is not recommended, especially in areas where you are growing edibles. Unfortunately, like you have mentioned, the only way to get rid of oxalis is to remove all of the bulbs by hand.
To do this, first divide the area up into sections then dig down 20-30cm and sieve the soil to catch all the bulbs. Admittedly, it’s a tedious task but well worth doing. Alternatively you can dig up the area, pen it off and put chickens in there. Once all the bulbs have been removed, replenish the soil with Daltons Compost and Daltons Big Value Blood & Bone.
If you decide to start over your vegetable garden somewhere else on the property don’t transplant the soil as it will only take a few bulbs to start the problem again!