As I drove through town a week before the autumnal equinox, the striking ivory flower stalks of a mighty yucca were on every street. The hefty plants are decades old, most likely, as their swollen stems and overgrown bases attest. This North American native plant that grows from North Carolina south into Florida and west toward eastern Louisiana finds Santa Barbara very much to its liking. It is Yucca elephantipes, sometimes known as the spineless yucca. Or is it? Plant taxonomists are of mixed opinion about this wonderful landscape specimen. Maybe it is Yucca gloriosa, or maybe it is a hybrid of unknown parentage. For plant lovers, it just doesn’t matter; it is a spectacular focal point in many Mediterranean-area gardens (yes, it can be found in the South of France, Monaco, and more). The current question is this: Why is it in full bloom now? All the plant encyclopedias and Internet sources say that it should be blooming in late spring or early summer. Huh! Enjoy the show whenever the curtain rises.
There are other yuccas that make great drought-tolerant landscape subjects, too. The native one that signals the beginning of summer here, usually in early June, is Yucca whipplei, commonly called chaparral yucca, Spanish bayonet, or our Lord’s candle. What a poetic name! It does have fabulous and showy flower spikes that regularly punctuate the hillsides around that time. This yucca grows in the midst of other shrubs and herbs that are beginning to fade into the summer drought season. Suddenly, the juicy asparagus-like stalk appears, up to 12 feet above the crowd, and then bursts into bloom. The creamy white blossoms clothe the stately stalk for a fairly brief moment: perhaps a couple of weeks as the individual flowers bloom in succession. Should one be hiking nearby (not really likely as the habitat is quite exposed and dry), the flowers are lightly fragrant and secrete a generous amount of nectar.
This brings us to a fabulous story of plant/animal interaction; yuccas rely on specific moths to pollinate them so that seed can be produced to continue the species. These night-flying moths have a little sup on yucca nectar and then snooze in the relative comfort of the flower during the day before venturing out to visit another blossom, carrying a load of pollen as they go. But their real purpose is to find a suitable nursery for their offspring. If the mother moth can successfully pollinate a flower, the flower stays on the plant and ripens its seeds instead of quickly falling off. The eggs that the moth lays will then hatch and have a food source in ovules that actually develop abnormally to nurture the caterpillars. Other larvae develop in the soil and at a different rate so that they are pupating while the seeds ripen. Wow, right? Okay, one more twist: Moth larvae that mature from eggs laid in the soil may do so at intervals lasting as long as three years, so that even if the seasonal climate doesn’t induce flowering in any given year, there is a reservoir of pollinators available for the coming years.
That’s the natural history of these amazing plants, but, of course, landscapers have found many ways to include their spiky forms in gardens. Other species, especially the stemless Yucca filamentosa, are widely planted. Variegated selections such as the yellow-striped one, ‘Bright Edge,’ and ‘Color Guard,’ which displays white or cream stripes, are container plants in northern and eastern gardens for their exotic good looks.