You see the oxalis growing wild out on the coast where it is wetter in summer than farther inland. And you see it growing in low and flat places.

The bleeding heart grows wild farther inland but is characteristic of low, moist rich woods where a typical associate is vine maple. In my neck of the woods you will see these two in hollows and pockets where surely the critical factor is that the soil does not get as dry in summer as in surrounding areas.

Of course, wild plants here have to survive everything nature throws at them in order to persist. In the garden we can usually get out the hose during a crisis or throw on mulch beforehand. Local plantings have both of these species in situations that appear to get pretty dry; the shamrock seems to be quite enduring but the bleeding heart will go into a summer mode of markedly reduced activity and beauty if not assisted.

A lot will depend on the texture of your planting site soils, with retentive ones offering a much better buffer against drought effects than sandy ones.

Both are probably included in the UBC Press forestry handbook Indicator Plants of Coastal British Columbia. If you find that at a library (it came out around 1989, I believe) you should be able to quickly get a good idea of the basic parameters of each plant.

Both appear on local lists of plants recommended for dry shade and you will find numerous references to both exhibiting significant drought tolerance once established.

Doesn't necessarily mean they will look their best under these conditions..........only that they will tolerate them well.

Thank you both! In my case I will do whatever I can for at least the first summer of establishment, and then hope for the best. I buried the root system deeper than I think they'd have appreciated (they both naturally creep sideways) in hopes it would allow more access to moisture.
Will have to wait and see.

Indicator plants of coastal BC... Sounds like the perfect source for info on quite a w plants I'm interested in, will look this up.