This tough native xeriscape shrub is seldom given credit for being a broadleaf evergreen, but in the duldrums of dry summer and in the winter, these plants are very useful. I especially like to see it piercing through the white snow in its green, bold, formal, sharp rosette. The stilleto-like leaves are 1’-2 1/2’ long and rosettes increase from the rhizomatous roots. In the garden these off-sets can be cut off with a spade if the plant needs to be kept from spreading. The very sharp leaves are difficult to weed around so I use a dense groundcover around mine (Sedum spurium ‘Bronze Carpet’ makes a nice contrast). This very sharpness which the plant has developed to keep from being browsed to death, can be employed to protect other more delicate plants, like a clump of species tulips, from the deer and rabbits. These yuccas are also useful for traffic management, so best kept a good distance from walks and entryways.
The flower is trul remarkable, lily-like, bell-shaped and fragrant, usually greenish-white. Whereas the leaves will grow under the worst dry, neglected conditions, the flowers appreciate a little water. (i.e. they may not flower every year in the wild.) These flowers are pollinated by the pronuba moth whose larvae are then raised on the numerous black seeds. Once the flowers have been in bloom for a while, they frequently get covered with aphids. This soon becomes a disgusting sight so at first I would cut off the flower stalk at this stage. However I now leave them in my garden after making a remarkable discovery.
During research into alternatives to pesticides, I learned that there are thousands of species of aphids and 90% are very host-specific, feeding on only a few closely related plant species. This gave me an idea: Why not leave certain weeds and plants that attract aphids and use them to feed and increase populations of lady bugs and other beneficial insects? Sure enough, now when I leave the yucky aphid-smothered flowers on my yuccas, the lady bugs show up and before long their orangy alligator-looking larvae are crawling all over the garden eating aphids. Whereas the yucca aphids won’t eat my roses, the lady bugs eat all kinds of aphids.Another bonus is that lady bugs like to overwinter at the base of yuccas, guess why?
There are several other garden-worthy and hardy varieties available in our area:
Yucca filamentosa- taller flower spikes,4’-7’,less drought-tolerant, more shade tolerant, leaves are not sharp.
Yucca baccata- flowers on 2’ stalks, wide, blue-green “sword” leaves
Yucca harrimaniae-native dwarf, only 10”-12” in diameter
Hesperaloe parviflora- not a true yucca, but looks the part, is xeric, 18”-24” with fragrant red flowers; leaves are not sharp.