Yucca rostrata at the Denver Botanic Garden, March 2011

Succulents are hot-hot-hot – but not all of them can take the cold.

Yuccas are just one of many kinds of succulents, but among their ranks are some of the hardiest and most handsome succulents that can grow in Portland gardens. In fact, there are some sixty species and subspecies, plus dozens of cultivars, that happily thrive in our climate – and most of them also flourish in climates even colder than ours. While most yuccas are native to the southwestern US and northern Mexico or central America, some (Yucca glauca) are native as far north as the southern Canadian provinces and there are species that thrive in New England and cold central and eastern states of the US.

Yuccas are members of the agave family – itself a lily relative – which explains why their flowers are so darn attractive and sometimes even fragrant. The plants are deer-resistant and the flowers are hummingbird-attracting. Most are drought-tolerant, thriving in situations where little to no water is needed (although they can grow faster with occasional water). They are visually striking, with bold rosettes of lance-shaped leaves. Some even develop statuesque trunks – the kinds of trunks you associate with plants of the desert Southwest. Yuccas make fantastic container plants but trunked yuccas are some of the most fabulous of all, with the combination of those attractive trunks topped with spectacular globes of spiny green or shimmering blue-green leaves. There are even yuccas that tolerate light shade. Yuccas range in size from less than a foot tall and wide to well over ten feet tall over time.

So which ones can survive our cold, wet winters, and which will simply turn up their little spears and melt at the first hint of brutal East wind? Peruse this list for a selection of cold-hardy yuccas – many trunking types – for our area; then look them up via the links below to see which forms require extra-good drainage, which tolerate a bit of shade and which, you know, tickle your fancy.

The source of the original plant material can make a big difference in hardiness with yuccas, as with any plant. The nurseries listed below seek to supply the most cold-hardy plant material available of each species.

Like yuccas that look like porcupine lollipops? I do. Here are some of my favorites – but there are many more available – some just recently named or available in cultivation. Some of these species form a single, upright trunk; others tend to form multiple trunks. Most grow s l o w l y so if you want to see some trunk, start with the biggest plant you can get. Or, just be patient. And if you’re worried about cold hardiness, note that most of these plants grow merrily at the Denver (yes, Denver Colorado) Botanical Garden. (The yucca-rama slideshow is from a trip I took to the Denver Botanic Garden this spring.)

Yucca aloifolia (zone 7) 5-15’ tall
Yucca baccata (zone 5) 8’ tall
Yucca elata (zone 6) – 6-10’ tall
Yucca brevifolia Joshua Tree! – (zone 6) 8-20’ + tall
Yucca faxoniana (zone 5) 8-18’ tall x 5-8’ wide
Yucca gloriosa (zone 7) 4’ tall or so
Yucca linearifolia (zone 7) 4-8’ tall
Yucca recurvifolia (zone 7) 4’ tall x 6’ wide
Yucca rigida (zone 7b) 12’ tall
Yucca rostrata (zone 5) 4’ tall
Yucca rostrata ‘Sapphire Skies’ (zone 5) 4’ tall – Portland’s own Sean Hogan selection of Y. rostrata
Yucca schotti (zone 7 or colder) 6-15’ tall
Yucca thompsoniana (zone 5) 6-8’ tall x 4-6’ wide
Yucca treculeana (zone 7) 15’ tall x 8’ wide

Who would have guessed there were so many? And this is just a snippet of what’s out there… in another post, I’ll show off some of the dishiest variegated and dwarf yuccas I’ve seen, which make such wonderful container subjects, particularly in winter.

…and now, a word of caution: yuccas (as well as agaves, hardy cactus and other succulents, can really hurt you if you get poked in the wrong place (I’m particularly thinking of the eyes, since they’re vulnerable, but there are several other wrong places I can think of). Plant them with care.

Sources for unusual yuccas:
Cistus Design Nursery
The Desert Northwest
Rare Plant Research (call directly for availability)
Yucca Do Nursery
Plant Delights Nursery