The fifty or so specie of yucca that are native to North and Central America are horticultural nonconformists. Like most of the related agaves and aloes, they are classified as succulents; but none have succulents leaves. Their stems store moisture, but are about as succulent as trunks of palm trees. Actually, many are classified as trees because they develop heavy and sculpturally branched trunks, but they are really just big herbaceous perennials that get very old.
From the Big Bend region of Texas and adjoining Mexico, beaked yucca, Yucca rostrata, happens to be one of the yuccas that develops a trunk, but grows so slowly with such billowy foliage, that it respected more as a striking foliage plant. The largest and oldest plants get no larger than fifteen feet tall and rarely develop one or very few branches. Most are less than ten feet tall with single but bulky symmetrical foliar rosettes. The individual grayish leaves are limber and narrow, but very abundant. ‘Sapphire Skies’ has even more striking bluish foliage.
As if the excellent foliage were not enough, mature beaked yucca blooms with small white flowers on big spikes nearly two and a half feet tall. Spikes can appear through winter and are typically finished blooming by spring, before summer dormancy, but do not seem to be too devoted to any particular schedule.
Beaked yucca is less common than it should be; perhaps because it is difficult to grow in nurseries. Besides, they are not for every garden, and are very likely to rot where they get watered as frequently as most other plants get watered. They do not mind if watered perhaps a few times through summer, but are more than satisfied with what they get from rainfall.
Although a relatively small agave, the Queen Victoria agave, Agave victoriae-reginae, is also one of the most striking. Mature plants form dense foliar rosettes that are between only a foot, and a foot and a half tall and wide. What is so striking about them is the abundance of stout succulent leaves that can be so densely set that some older plants look like big, round and green pine cones.
From a simple picture, Spanish bayonet, Yucca aloifolia, is indistinguishable from the common giant yucca. The narrow leaves are about two feet long, and flare upward and outward from terminal buds. Plump conical trusses of waxy white flowers with purplish highlights stand vertically just above the foliage. The main difference is that the leaves are more rigid than they appear to be, with nastily sharp terminal spines.
Yuccas are almost as useful as aloes are for gardening in chaparral or desert climates. I say ‘almost’ because most are not quite as friendly. The leaves are outfitted with nastily sharp tips. It is how they protect themselves from grazing animals in the wild, but it is not such an advantage in home gardens. Some actually have the potential to be dangerous where someone could bump into them. The leaves of Joshua tree can puncture leather. Some types of yucca get so big that they make it difficult to avoid their nasty leaves, even if planted in the background.
We really should be growing more of what grows well here. This is as relevant in other regions as it is in the Santa Clara Valley. Some regions have a lot more to choose from. There are always limitations too. Tropical plants do not survive the winters of New England. Apples and pears want more winter chill than they can get in San Diego.
Tony Tomeo 