Capparis spinosa, aka, caper bush is a fruiting plant (not a vegetable) native to the Mediterranean region, parts of Asia and the Arabian peninsula. When I visited southern Italy two years ago, healthy caper plants were growing wild in rock crevices, ancient stone walls, road cracks, and hard dry ground with no irrigation. The temps were in the low 90's, however it felt more humid there compared to Northern California.
The first two pictures below were taken in the warm Puglia region. Capers are harvested by hand as tiny green unopened flower buds, sun-dried, and then pickled for use in Italian cuisine. If the buds are allowed to bloom, they eventually become crunchy berries, which are also edible pickled or salted. Even the leaves can be used in cheese making.
The first picture shows a small plant growing in a crack on the rough road, with no water source.
The second picture has a large, beautiful plant growing in a stone wall. In their native habitat, caper bushes can grow as large as three feet tall to six feet wide. Caper plants can supposedly survive several months with no water.
The final picture below shows a little seedling that I was delighted to come across at a local independent nursery. The nursery first tried propagating cuttings but found that they did not always survive and took up to a year to grow. They found growing from seed to be the most effective approach. There won't be intentional experimenting on this pricey plant's ability to survive months without water. Early on, I left it a mere two days, and some leaves shriveled up. Perhaps the lack of moisture in the air here makes a big difference. Right now, we are in the midst of a severe two-week heat wave, and today, I finally decided to take a break from the exhausting early morning watering of our yards. Alas, I forgot to water the caper especially! One can only hope my plant has acquired a little of its Italian cousins' invincibility…
Cheers, and Chill!