I too am an Oxalis fan and every year give offsets to the BX. I'm just passing on the generosity of Mike Mace who shared many offsets in the beginning from his IBS Michael Vassar collection. I still remember him describing his delight when his wife gave him the collection as a present and how he stayed up late planting them since they were already growing. A lot of Oxalis enthusiasts are very generous with their extras. Bill Baird, Uli, and Ron Vanderhoff have all shared with me too. And Diana at Telos sells a lot of wonderful species so it isn't hard to get started (at least in the US) and much too easy to become addicted/passionate. I've found the winter rainfall species from South Africa do best for me if I start watering them in August which is earlier than I start watering most of my winter growing bulbs. This means that the early blooming species can start flowering in September and put on a dazzling display of color during the often sunny days we have in fall. Besides the bright colorful flowers and the long blooming season, I also love the variety in the leaves. Oxalis pes-caprae is the one to watch where I live where it has naturalized and taken over in many areas of coastal California. Oxalis purpurea is likely to spread and be hard to eradicate too for me if planted in the ground. It also doesn't bloom for me in the shade which a lot of my property is so I regret the few experiments where I tried it in the ground, beautiful though it may be. However, if you have a place where you don't care if it takes over, it is carefree and blooms for a very long time. I've tried a few Oxalis in the ground like obtusa and they have disappeared. I've grown others in pots in raised beds where I haven't repotted them and have had better luck with a few species like O. flava and O. luteola, but they don't bloom quite as long it seems as when they are repotted each year. At least that's my experience. Living in an area with a lot of winter rainfall and dark days, I expect my plants will never have the tight form that plants do in South Africa and southern California. I often grow a number of them in a cold frame where there is sometimes just enough extra warmth to have the flowers open in winter. Oxalis gracilis is not a strong bloomer for me and Oxalis inaequalis was an early casualty. I did see it bloom briefly one year and was surprised how huge the flower seemed in relation to the size of the plants. So neither would make my favorite list although I like the color of Oxalis gracilis. I think my ten would have to be influenced by which was blooming at the time so if you asked me at different times of the year I might give different answers. But I share some of the favorites that others have mentioned and it's difficult to choose since ones I don't have on this list I'm very fond of: Oxalis bowieii -- fall bloom, large bright pink flowers for a long time Oxalis convexula -- I like the succulent leaves of this species Oxalis elegans -- summer growing species from Ecuador from Uli, or at least that's what we think it is, long blooming in summer, could be hardy if you stored it appropriately since I just leave mine dormant in winter and don't start watering until spring Oxalis flava -- fall bloom, lots of variety in leaves and flower color, long bloom Oxalis hirta -- nice fall blooming plants although they need a deep pot Oxalis peridicaria (syn. O. lobata): I too love this one from South America with its bright yellow flowers Oxalis luteola: I have three forms of this one, one with spotted leaves that does not offset much. I love all three. Oxalis obtusa: Some years some of the forms I grow bloom for three or four months. Lots of great variety in these, but there is a pink one that appears in a lot of pots and I wonder if it seeds itself about Oxalis palmifrons: Grown for the leaves Oxalis versicolor: Another favorite in bud and flower Mary Sue