Hardiness

Apperently it seems as some summer growing oxalis with bulbs or rhizomes can be somewhat hardy.

I´m still trying to investigate how hardy. For now please look at the endividual species in the Summer Growing Oxalis page, were this slow proces can be mention

Taking Care Of Your Summer Growing Oxalis

Bear in mind that the following growing experiences are gathered under danish weather, why growing conditions in your area should be taken in consideration.

Starting the growing season

For most parts I start these species growing season in late April or when night temperatures are 5 C / 41 F.

That is, if they have not started to grow sooner on their own. If they have, I have only one option. Take them outside, water and bring them in at night, as an oxalis can become destress or die if it is not allowed to grow when it´s ready.

Why take them outside? read a little about etiolation.

Growing needs

Most of these oxalis species need well drained soil and moist conditions.
Mine are planted in regular potting soil that is not to rich, although alpines need a mixture of ½ regular potting soil and 2 parts pebbles, or they can rot.

Oxalis adenophylla sp. grown in a mixture of pebbles and potting soil.

Oxalis Tuberosa

If you are planning to grow Oxalis Tuberosa also know as occa, there are a few things you should have in mind.

Oxalis Tuberosa needs a longer growing season and depend on day length, as they first form tubers when day length shortens in autumn.
In areas with harsh winter climate, the cold can kill the plant before the tubers are completely formed.
Whereas in tropical areas, where day time is evenly longer, the Tuberosa can have difficulty setting a successful crop, as the days are not short enough.

But it is an oxalis worth growing, and it never hurts to try, now does it?

Try this site if you would like to read more regarding Growing Occa

Oxalis Acetosella from Flora Danica
if I had the money....