In the Garden: Please Pass the Asparagus

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Yucca rostrata
Yucca rostrata

By Charles Kidder

The Asparagus family (Aspara-gaceae) consists of 114 genera and about 2,900 species, including Asparagus officinalis, the plant we grow in our vegetable gardens. Of potential interest to ornamental gardeners are a few genera sometimes known as the woody lilies.  Like the true lilies, these “woody lilies” are also monocots—i.e. a large group of plants that include the grasses—but in actuality they aren’t truly woody, nor are they lilies. Putting terminology aside, let’s look at one genus that can be grown easily in western Albemarle County.

As perhaps the best-known genus of this family, at least one yucca species grows wild—or perhaps escaped from cultivation— across much of Virginia, and they have won acceptance in (nearly) mainstream horticulture. True, some people are totally put off by “spiky” plants—including even upright conifers—but to those with more open minds, an evergreen shrub requiring no supplemental water or pruning and sporting a bold flower spike…what’s not to like?

The approximately fifty yucca species are all native to the Americas and have been employed by native peoples and later immigrants for a variety of purposes. The dried leaves have a low ignition temperature and can be useful for starting fires. The leaves’ sharp points and tough nature allowed them to serve as meat hangers during curing.  The Cherokees used leaves, stems and roots to stun fish. But if you’ve ever eaten “yuca” in a Hispanic restaurant, it has no relation to yuccas; rather it’s the root of the cassava plant, Manihot esculenta.

The aptly named Yucca flaccida has pliable leaves that are not very likely to produce an “ouch” unless you really work at it. Sometimes given the name weak-leaf yucca or hairy soapwort, it typically attains a height of only 18”-24”, not including the much taller flower stalk. It does like to run, however, so lop off the young offsets if you don’t want to create a sizable patch.  Then again, this spreading tendency would be highly desirable if you want to cover a large slope. Many of the available cultivars are variegated with yellow coloration either at the edge of the leaves or in a broad stripe running down the center. Common varieties are “Golden Sword,” “Color Guard,” and “Gold Heart.”

Yucca filamentosa
Yucca filamentosa

Speaking of names, Yucca flaccida is sometimes confused with Y. filamentosa  (Adam’s Needle or Spoon-leaf yucca). I don’t intend to delve deeply into taxonomic details regarding their differences, especially since I would probably be proven wrong within five minutes. That said, Y. flaccida would appear to have the more relaxed leaves, Y. filamentosa, the more rigid ones, especially the younger leaves at the center of the rosette. Also, Y. filamentosa is known for the white, thread-like filaments at the leaf margins, an ornamental feature that can be appreciated at close range. To further the confusion with Y. flaccida, the cultivars “Color Guard” and “Golden Sword” (see above) are sometimes assigned to this species. Don’t sweat the names. If you see it and like it, buy it.

Although the smaller non-trunked yuccas have become more common in mainstream gardening, one warning note was sounded by the Missouri Botanical Garden’s website. The yuccas increased use in fast-food restaurant landscapes might lead to a negative association for homeowners. I still stick to my “if you like it, plant it” mantra, however. Just don’t surround your variegated yuccas with red-dyed mulch.

If you’re truly adventurous you can try planting the trunked yuccas. One of the hardiest is Yucca rostrata, beaked yucca, a native to northern Mexico and one county in Texas. Beaked yucca can reportedly reach fifteen feet in height in ideal conditions. A couple of beaked yuccas I observed in the North Carolina Piedmont have grown from one-gallon size to four feet tall in ten years. Yucca rostratas typically bear light bluish-green leaves with a slight twist and are arranged in a roughly hemispherical shape at the top of the trunk. If the plants are in an open area, the leaves can flutter hypnotically in the wind.

In yet another chapter on confusing yucca species, Y. thompsoniana and Y. linearifolia are quite similar to Y. rostrata. The former tends to be shorter than the beaked yucca and will reportedly flower even before forming a trunk. Yucca linearifolia has narrower leaves, and retains additional tiers of green leaves below the main rosette. And speaking of leaves, the older ones cling to the trunks of these three species in grass-skirt fashion. If you were particularly (overly?) tidy and had a lot of time on your hands, these could be trimmed off.  However, the old leaves provide some protection from direct sunlight and excessive temperature swings.

One possible issue with the trunked yuccas: Do they look “right” in the Piedmont of Virginia? True, probably not much of a problem for dedicated plant nuts, but your realtor might have a fit when it comes time to sell the house. Or if you’re lucky, you’ll have a Mediterranean style home, and the yuccas would work fine.

As for culture, yuccas generally prefer full sun and good drainage. That said, they also seem tolerant of much different conditions. I’ve seen older plants—20-plus years?—sited in unamended clay with a gravel mulch. I have also grown them in clay with no apparent problem. Partial shade is okay also, although you may not get much flowering.

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