I have grown Oxalis 'Ken Aslet' for many years in the bulb frame,
where it does flower freely. I let it dry out quite a lot in summer,
and it pops up in fall like most of the other bulbs. I also have it
in the open garden but I think the buds are damaged by cold and rain
there. Still, the foliage is decorative and it is not an invasive plant.
Some years ago I bought different color forms of O. obtusa from Telos
Rare Bulbs. Only one color survived, so it must be more cold-hardy
than the others. It is a yellowish pink ("peach") and has infested
the plunge medium in the bulb frame pretty widely. It also turns up
in the open garden, where the weather keeps it severely checked -- it
barely spreads there. Although it obviously has invasive potential
were the climate here a bit warmer, it is so lovely with its tiny
gray leaves and huge flowers that I enjoy it. It is too short to
swamp nearby plants.
Jane McGary
Northwestern Oregon, USA