Rugged Yuccas: Bear Grass on the Grow

By William Scheick, Contributing Editor

Twist-leaf yucca (Y. rupicola) has long been an Edwards Plateau native thriving on my rock-strewn property in southwestern Travis County, TX.

With solitary or clustered rosettes of finely serrated leaf-ribbons (about 2-feet long), they aren’t very impressive most of the time. It’s easy to undervalue these resilient perennials as evergreens that readily accommodate local climate extremes. Even the rare ice storm doesn’t faze them.

During spring, however, twist-leaf yuccas make a very different impression. That's when they sprout sturdy 5-foot stalks abundantly adorned with large, white floral bells that insist on being noticed by people during the day as well as pollinating moths during the night.

Even so, slowly spreading clumps of somewhat droopy, thin-bladed twist-leaf yuccas will probably never gain wide appeal as garden options.

Their curling foliage is often a prominent feature, but some of mine don’t twist at all. Possibly these are hybrids, since twist-leaf yuccas crossbreed with (hue-variable) pale-leaf yuccas (Y. pallida) and maybe also with other related species.

In fact, nodding yucca (unofficially Y. cernua), found only in a 6-square mile area of East Texas, is suspected of being a hybrid of the twist-leaf and the pale-leaf species.

Adam’s needle (Y. filamentosa) is a Texas native also found throughout the eastern half of the U.S.

Sounds yucky, but it's not

Sometimes I wonder whether such neglected tough perennials deserve a more inviting name than one that sounds like “yuck.” After all, the strange name they presently carry stemmed from a misunderstanding in 1593.

Then, Englishman John Gerard had received a plant from the New World that he wrongly thought was luca. This Caribbean Taíno word referred to the starchy tubers of Manihot esculenta, the source of cassava and tapioca among Indians of South America. Even after this error in identification was revealed, the name luca/yucca stuck.

Bear grass

I prefer to think of these plants more poetically as “bear-grass,” Thomas Jefferson’s name for the yuccas grown in his gardens at Monticello, Virginia.

Meriwether Lewis, who reported to Jefferson during his famous fact-finding expedition to the Pacific Coast, was pleased to stumble on “a great abundance of a species of bear grass.”

Its “growth is luxuriant and continues green all winter,” he wrote in his notebook in 1806, adding the further good news that the newly found yucca is too fibrous for horses to eat.

The phrase “bear-grass” aptly conveys the toughness and endurance of our North American yuccas, which in Jefferson’s time were considered to be attractive candidates for gardens in both Europe and America.

A glance at bear grass foliage reveals some of this hardy plant’s survival secrets. The serrated edges of many yucca species’ leaves sometimes deter trampling by animals and likewise, as Lewis noted, that same foliage tends to be too fibrous for foraging.

Also, long narrow leaf-straps such as yucca’s limit under-surface area, a strategy reducing these plants’ vulnerability to moisture loss (transpiration) in heat and wind. Many yucca species further restrict water loss by producing either a waxy, oily or hairy surface on their foliage — surfaces that reflect and insulate.

Some yuccas store sap in their thick leaves (similar to succulents), while most yuccas store carbohydrates in their inedible bulky roots. Just below the crown of one of my twist-leaf yuccas, for instance, I found a bulb-like structure. Out of this “bulb” a thick root descended deeply into the earth and formed (at its tip) another swollen storage organ safely buried far below the plant’s surface environment.

Twist-leaf and other “bear-grass” with basil rosette designs collect water — sometimes as meager as dewy condensation — that funnels downward to these deep roots and carbohydrate “banks.” Such nutrient-rich storehouses even survive wildfires and can sprout new foliage soon afterwards, as the dogged twist-leaf yuccas in Bastrop have demonstrated among the scorched remains of the loblolly pines (Pinus taeda) burned in 2011.

Bear grass gardening

Obviously, bear grass," like its agave cousins, could be a welcome garden addition in the droughty regions of our state. Incidentally, a Lone Star garden favorite, the so-called red yucca, is actually Hesperaloe parviflora, a Chihuahuan Desert yucca relative.

Referred to as xerophytes because they have adapted to dry landscapes, yuccas are no-nonsense, low-care perennials in granular soils with good drainage. Unlike many agaves, most yucca species do not die after blooming. And their stalks of branched white or cream flower clusters (panicles) are gorgeous even if, unfortunately, the blooms are vulnerable to deer appetites.

• Plant bear grass outdoors during spring or early fall.
• Most prefer plenty of sunlight, although new transplants need protection from burning and desiccation.
• Position these plants for excellent drainage on a slight slope or a small sandy or rocky mound, also keeping them safe from pooling rainwater during storms.
• Always position their crowns higher than ground level to avoid rot. During dry periods, water directly on the clumps or rosettes (which funnel to the roots).
• Prune only damaged or spotted blades. And, to play it safe, cover small yuccas during hard freezes.

Based on such effortless care, drought tolerance and spring showiness, bear grass should be relatively popular as a garden plant in Texas.

However, the appeal of yucca as a yard plant is not instantly obvious to many gardeners.

Possibly the main issue is: how to solve design challenges posed by the architectural flair of yuccas? With bear grass, the trick is to balance their strong sculptural presence with other plants or features providing prominent contrasting patterns.

Mastering this trick is easier with yuccas than with agaves, which convey a much starker “stand-alone” or “stand-offish” effect.

Companion plants for bear grass could include coneflowers, yarrows, sages, tradescantias and native grasses. Coming in many shapes, sizes and colors, lantanas are particularly apt choices to pair with bear grass because they share the same harsh growing conditions and bloom so prolifically.

Mounding vegetation, prickly pears, or ornamentally arranged rocks also offset yucca’s dominance, which can likewise be counter-balanced when bear grass is grown in high, attractive containers rather than in the ground.

Clumping and tall yuccas look especially good, too, while filling in open gaps and contrasting with the horizontal wood of ranch-type fencing.

Bear grass selections

Companion planting depends on the bear grass species you choose.

Yuccas come in a variety of forms ranging from stemless and grass-like (Y. elata, Y. glauca) to trunked and tree-like (Y. brevifolia, Y. thompsoniana). Some produce rigid fans (Y. faxoniana, Y. rigida), while others offer arching or curling foliage (Y. recurvifolia, Y. rupicola).

There are (as we saw with Y. rupicola) rosette forms, including Y. baccata and Y. whipplei. Yucca foliage can be smooth, rough and even hairy (Y. faxoniana). Leaf edges are smooth in some species or moderately serrated, such as the blades of Y. filamentosa.

Bear grass varies in color, offering a surprising array of greens. While glossy and gray-green predominate, pale blue has become a fashion statement among yucca collectors. The ‘Mexican Blue’ cultivar of Y. rigida, the ‘Sapphire Skies’ selection of Y. rostrata and the ‘Blue Twist’ hybrid cross between Y. rupicola and Y. pallida have bear grass enthusiasts singing the blues — from joy rather than sadness.

Variegated yuccas can also make striking additions to the garden. The leaf margins of clumping ‘Bright Edge’ (Y. filamentosa) are gracefully lined with white or creamy-yellow stripes. A yellow blade-band is centered on the foliage of ‘Color Guard’ (Y. filamentosa), and during winter it turns pink-red. Each leaf of the rosette-forming ‘Banana Split’ (Y. recurvifolia) is variously striped with green, blue and yellow bands.

Bear grass beginnings

When thinking about the suitability of a particular bear-grass for a garden, yucca expert Mary Irish offers helpful advice. “The immense trunked form tends to hale from the deserts and dry mountains of northern and central Mexico," Irish said, "which is the epicenter of yucca distribution throughout North and Central America."

Irish recommends this practical rule of thumb: the bigger the trunk of a yucca species, the greater the likeliness that it originated from — and will thrive in — hot and arid conditions. 

Thompson’s yucca is native to the Trans-Pecos region of Texas.