Opuntia nemoralis (2020)

Prostrate growth of Opuntia nemoralis. The plants tend to generate two new pads in one season, with the older growth becoming corky over time.

By Pat Mahon (July 2020)

This month, I’d like to keep it simple and share a fairly rare species of prickly pear, Opuntia nemoralis. This species has often been lumped with O. humifusa, which comprises a polyphyletic (many ancestors) clade, but differs by the monochromatic yellow flowers and smaller morphology.

The species was originally discovered by David Griffiths in Longview, Texas, in 1911, and described as a new species in Monatsschrift für Kakteenkunde Vol. 23 (1913). Today, the species is restricted to where the type specimen was found in Texas and in shale outcroppings in Hot Spring County, Arkansas. There is also another reported extant population in Louisiana, so it does seem that the populations are fragmented.

There’s not much to garner from Griffith’s description, but the specific rank for O. nemoralis was restored in 2017 due to a taxonomic revision of the O. humifusa complex. The plant is very easy to grow, and in the spring creates two new pads of growth. Flowering seems to occur in May, but may be dependent upon the presence of acidic conditions and minerals in the shale deposits.

Flowering O. nemoralis at Sonnia Hill, Texas. Photo by Joe Shaw and Barry Snow,

It was also noted this species can be found in pine woods and sandy prairies, which all tend to have the characteristic acidic conditions.

We will be trialing this species outside in Missouri’s winter to understand if it can be another hardy species to grow here. In the meantime, we will attempt to understand how to initiate flowering of this plant, in hopes that we can produce seed. It does not seem to freely produce flowers like O. humifusa or O. ficus-india.

Not much more is known about this species, since it is not in cultivation, but there has been extensive molecular work done on it and related species.

Sources: – Genome Sizes and Ploidy Levels in Mexican Cactus Pear Species Opuntia
U.S. National Library of Medicine PubMed Central – Cytogeography of the Humifusa Clade of Opuntia
Biodiversity Heritage Library
Monatsschrift für Kakteenkunde
Phytotaxa – Taxonomic Revision of the Opuntia humifusa Complex (Opuntieae: Cactaceae) of the Eastern United States –