The primary leaves have a durable petiole which develops into a protective thorn when the leaf is shed. The plants are a sensitive indicator of surface moisture, and the leafless, gray, thorny stems sprout secondary green leaves immediately after rain. These leaves are different from the primary leaves, in not leaving a thorny midrib behind when shed. The leaves are lost as the soil dries out but may re-appear several times a year, depending on rainfall.
In Southern Arizona I have seen cut stems of F. splendens used as reinforcement in lath and plaster or adobe house walls which had crumbled with age to reveal their internal structure.
Cultivation of F. splendens
A stem cut off and stuck in the ground will grow in a warm, frost-free climate. In Mexico and parts of Arizona the Ocotillo is traditionally used as a living thorny fence, testifying to its ease of cultivation.
In the UK, Fouquieria splendens grows well in an unheated, frost-free conservatory throughout the year, but especially well during cloudy cool weather which seems to act as a stimulus for leaf production. The plant should be watered liberally when leaves first appear, and a little water given from time to time until the leaves are seen to begin to go yellow and die. When this happens, further watering will not save these leaves: to avoid the risk of damage to the roots and lower stem it is best to withdraw water and allow the plant to rest. A little water may be given from time to time during dormancy to see if conditions are correct to initiate leaf production.
My plant continues in leaf during the winter months if given a little water, and I have known it produce 2 in (5 cm) of stem growth at this time of year. It is potted up in a very gritty mixture in keeping with the gravelly soils in many parts of its natural distribution. F. splendens can be seen to thrive on a wide range of soils derived from limestone, sandy and igneous material suggesting that soil pH is not critical. On the last occasion of re-potting my plant, the roots were mainly near the surface of the compost and not utilising the full depth of its 5 in pot, so it was replanted in a shallower but wider clay bowl.