A Gardening Journal
Mexican Grass Tree
- Published: November 23 2014
I was lucky to have been able to visit California's Bay Area this month. Its subtropical climate is so welcoming it's difficult to tolerate: You can grow directly in the garden much of what we prize back East—beech trees, Japanese maples, many of our perennials—plus most of what we can grow only via containers and greenhouses. Even generic tree-pit plantings can be an impossibly lush mash-up of what, for us, would be priceless conservatory specimens and workaday stalwarts: Boxwood at the base of a palm tree, say, just barely holding its nose above a surf of aeoniums and amaryllis.
Despite the incessant beauty, you can't stop to gawk every twenty feet. The rest of life must go on; I had a wedding to attend, as well as friends to meet for dinner. Thank goodness, I was able to reserve time to visit two of the world's most important botanical gardens. In each, I was slack-jawed by horticulture that would be impossible back East, regardless of effort, time, or money—such as this massive, perfectly-groomed Mexican grass tree in the succulent garden of the San Francisco Botanical Garden.
Not a true tree, let alone a grass, Dasylirion quadrangulatum is a yucca cousin whose countless three-foot leaves are wire-thin. (And quadrangular, i.e., four sided, in cross-section.) They emerge from a central growth tip, arching farther and farther out as newer leaves slowly extend the trunk-like center higher. Leaves remain attached even in death; here, the lower trunk has been shorn, while the upper brown leaves have been beveled into an elegant dias for the hemisphere of live foliage above.
At the very center, thrusting upward like a molten eruption caught by stop-action photography, is the yellow-green inner column of nascent leaves.
This astounding specimen is about twelve feet tall and, darn it, I didn't bring along a collapsible step-ladder—whose use, in any case, would have been verboten. A closer view of the very heart of life of this remarkable species seemed hopeless. But the next day, I was able to race across the Bay to the Berkeley Botanical Garden. And there, right in the entry bed, was another Dasylirion quadrangulatum. This individual's trunk was just a couple of feet tall and, even more important, its entire head of quill-like growth was within easy reach even while I remained on the pathway.
There was no use resisting. I had to riffle through the plant's sheaf of bluish foliage. In addition to the tactile experience of fingering the stiff leaves, I could spread aside the surrounding hordes of mature foliage to reveal the paler newest growth at the center. In fastidious demonstration of the color spectrum, quill by quill, outer to inner, leaf hues changed from slate blue to blue-green to creamy green to, at the lower core—the very youngest leaves, which normally weren't yet exposed to direct light—the green-free brightness of heavy cream.
Yes, this Dasylirion is just a plant—and yet, I had revealed something private. In respect (but not before snapping a couple of pictures) I withdrew. The foliage immediately reshuffled itself back to its vertical array, hiding the youngest growth from view even as the tall core of greenish leaves reformed the astonishing central column I had seen the day before.
I'll profile this sensational species soon. I'll focus on my containered specimen, which is several years too young to display the greenish "molten eruption." Its canopy of live foliage is still filling out a full hemisphere, so light penetrates right to the center. Even young foliage develops the slate-blue coloring that, for the much older and more densely-leaved specimens in these California gardens, is characteristic only of mature leaves.