Two friends have a thing for the California desert, and visit it pretty much once a year. The large terrace of their 13th arrondissement apartment has become a sort of homage to the Southwest US. I’m amazed that their cacti and succulents, some of which are several years old, have survived the Paris weather. The cold, my friends have told me, isn’t a problem, since it get cold in the desert, too. The key, they said, is to make sure the soil has no moisture in it whenever the temperature drops below freezing.