Yucca nana growing in the San Rafael Swell region of central Utah.

Yucca nana is such a cool little plant. It’s one of the most diminutive in the genus (if not actually the smallest) with mature flowering size rosettes spanning only 6 inches across at most. The short floral spikes are large for the plant but tiny for the genus, reaching only about 12 to 18 inches tall (30-45 cm). Commonly called doll house yuccas, these bite-sized plants (the epithet “nana” means dwarf or small) are found in the plateau country sandstone clefts of central and eastern Utah and probably in small parts of western Colorado and adjacent Arizona and New Mexico. They can form clusters of up to a dozen heads in favorable sites, but solitary or twin plants are quite common given their restricted habitat of shallow soil pockets and narrow cracks in extensive zones of barren rock. Blooming times are typically in mid to late May and into early June, depending somewhat upon elevation.

I snapped this photo just before a thunderstorm bore down upon me, dropping heavy rain unusual in late May for the region. You can see the canyon country slickrock already becoming speckled with raindrops. Back to the car to keep on driving!

It evidently takes the small leaf clusters of doll house yuccas a significant portion of their energy to support such relatively sizable flower clusters, with over half of the leaves dying back as they pump energy into the floral spike. But the thick taproots must also support the flowering process since they are capable of storing water, starch, and sugar reserves that enable the effort.

There is some disagreement among enthusiasts of yuccas who study the genus as to whether Yucca nana is a fully justified species or not. Many consider them to either be a subspecies of Yucca harrimaniae (ssp nana) or just simply straight up dwarfed forms of Y. harrimaniae without even rising to the level of subspecies. Yucca harrimaniae is a larger species that otherwise looks rather similar apart from its greater stature, with individual leaf rosettes reaching about 18 inches to 24 inches across, and taller flower spikes.

Yucca nana, growing in shallow sandy soil amidst expanses of slickrock in the San Rafael Swell region of Utah.

Personally, and this is just my opinion, I think these plants are reasonably well defined as a subspecies. It appears that the dwarfism exhibited by these plants is a stable characteristic once it manifests, and simply growing the plants under more salubrious conditions does not result in a significant size increase, thus indicating that the dwarfism is genetic, not environmental.

Habitat of Yucca nana in the geologically fascinating and beautiful San Rafael Swell region of central Utah.

But arguments against them rising to the level of full species exist as well. One includes a report from a friend who grows these on occasion that if a batch of seedlings is grown from one or two seed pods coming off of the same parent plant, about 80% of them will be dwarf, but that about 20% of them will be larger and more typical of Y. harrimaniae. Another is that since in botany many subspecies are separated out on floral characteristics as opposed to foliar ones, that Y. nana flowers are simply hardly any different from Y. harrimaniae. I don’t think it has been formally studied, but I strongly suspect that they are pollinated by the same species of  yucca moth as well.

This close similarity in both flowers and foliage with some plasticity in leaf rosette size does seem to indicate that the two species are very closely related and capable of hybridization, but are probably diverging into separate species over time. Perhaps if we were to check back in about a million years or two, we would be decidedly able to determine their distinctiveness. Until then, however, we can always just enjoy the miniature forms of yuccas growing in central Utah under the name of Yucca nana. 🙂