Euphorbia officinarum This rare spiky plant has thick branches covered in vibrantly coloured spines, hence the nickname pincushion! A real standout as well as being easy to propagate it is a very popular choice. How to care for your Euphorbia – Water: Water well only once the soil is dry and allow to drain fully. Light: They need bright full sun. Humidity: Dry conditions would be sufficient. Temperature: They need warm temperatures about 20 degrees C. Toxic to cats & dogs? No, but the spikes can hurt!