I have to chip in here, and I am not going to defend my favorite genus. I don't care if some people hate Oxalis. I NEVER reuse potting soil. I think it is totally crazy!! You are risking your collection. You could spread fungal diseases, root mealybugs and possibly virus among your precious collection in addition to seeds and bulbils that you don't want. Not to mention also that used potting soil is lacking in nutrients and probably has salt buildup from fertilizer application. It just isn't worth the price of a bag of potting soil. I generate mountains of used potting soil, and it goes on my flower garden (which is large), and yes, I have little bulbs popping up here and there, but I have never had Oxalis in my garden, mostly native bulbs, gladiolus and tropaeolum (which was a surprise). I repot everything about every two years, and it is a constant ongoing task throughout the year. I have hundreds upon hundreds of pots of bulbs, and all the old potting soil is discarded, and the pots and benches washed along with the repotting. If I can do it with a whole nursery full of bulbs in pots, you can too!!! I have NO problems with disease spreading in my greenhouses or with unwanted bulbs popping up. Diana Telos Rare Bulbs