Griffiths, Proceedings of the Biological Society of Washington 29(3): 13–14, 1916

Isotype; Herbarium; Herbarium; Herbarium.

Original Citation

What is Opuntia caesia?

Opuntia caesia is a prickly pear cactus that is larger than O. phaeacantha. It may reach 2-3 m across and be about 60-80 cm tall with erect branches that rise from spreading, sprawling branches.

Details

The main branches often rest on the ground with upright branches to 60(70) cm. Cladodes on this Opuntia are typically 11-15 cm wide by 20-24 cm long, though they are variable. The obovate pads may have a narrow base. New growth is glaucous and blue-green, sometimes pronounced, but becomes green or yellowish-green in age. There are 2-4 spines in the first year that are sometimes dark but which may be nearly white. The longest spines can be 5(8) cm long.

The flower is yellow brushed with red in the interior. The style is white and the stigma is globose and light green; filaments are yellow with greenish bases. The ripe fruit is purplish-red but the pulp is lighter.

Ploidy is unknown.

Other Notes

Griffiths remarked that this Opuntia has nearly as much glaucous blue bloom as O. robusta. The blue color fades to greenish or yellow-green under drought stress or with age.

The plants are abundant around Crozier, Arizona. This Opuntia shares similarities with O. camanchica and may be the same taxon. However, the blue color makes it distinctive, but that could just be a population-to-population variation.