A succulent grass? No way.

Yes way. New bamboo from Laos is first ever.

All of you gardeners out there, what comes to mind when I say the word succulent?  A cactus, perhaps?  Or, spurges.  How about bamboo?  No way, you are thinking — but not so fast.  The term succulent refers to any plant with specialized organs capable of storing varying amounts of water. They generally have structures that are thickened, fleshy, and (at least at times) engorged, to retain water in arid climates or soil conditions.  There are succulent species in more than two dozen families of plants, so the word does not indicate plants related to one another, but instead, those sharing this physiological characteristic.  Rather like the word tree indicates a particular habit or form and applies to plant species in many unrelated families.

We live on a planet with a great many kinds of grasses.  There are about 10,000 named species of grasses in the family Poaceae.  Collectively, grasses make up about a quarter of earth’s total vegetation.  Among them are the nearly 1500 species of bamboos, found on every continent, with the exceptions of Antarctica and Europe.  Bamboo has always been an unusual word to me.  It sounds like something Chef Emeril Lagasse might say in the kitchen on Halloween.  Its origin apparently was in the late 16th century, tracing back to a Malay word, mambu, or possibly samambu, a kind of rattan plant.  On its way to its current spelling — bamboo — it had variations in Dutch, spelled bamboe, and, in Portugeuse, bambu.

Typical bamboos are instantly recognizable as such to most people.  Although diverse, they are perennial, flowering, evergreen grasses, sometimes giant in size — including the largest of any grass.  In Southeast Asia, the giant bamboo, Dendrocalamus giganteus, typically reaches 98 feet in height.  And one clump in India was almost 138 feet tall.  Bamboo stems are usually hollow between nodes, with vascular tissues scattered throughout the stem instead of being in a cylindrical arrangement.  When I picture a bamboo, I think of a tall, straight, smooth, rigid column, marked periodically by rings at  nodes, rather than a smooth tapering stem like so many other plants. Among bamboos is the record-holder as the fastest-growing plant on earth, capable of growing about three feet in twenty-four hours!  That works out to about a millimeter every ninety seconds.

With so many bamboos known, and so many species resembling one another in structure, it’s rare to discover one that is different from all the others in some fundamental way.  But Thomas Haevermans, of the natural history museum in Paris, with colleagues from Laos, Brazil, France and China has done it.

They have discovered a new genus and species from Laos, Laobambos calcareus, that is the first succulent bamboo ever seen.  Found growing in cracks on bare rock, on slopes in a karst region, the new species forms shrubby clumps 2 to 3 meters high and 2 to 3 meters in diameter, often with more than 50 living stems.  Like any succulent plant, this bamboo is capable of varying the volume of water stored in certain tissues.  Specifically, tissue in the culms — that is, the woody stems — forms the organ that expands, taking up water during rainy periods, and shrinking during droughts to become deflated, leafless, wrinkled, and dormant.

Its water absorbing and holding capacity has to do with parenchyma cells, as no other specialized kinds of water storage cells exist.  Parenchyma cells form fundamental tissues in plants, from the pith in stems and roots to photosynthetic tissues in leaves, pulp in fruits, and endosperm in seeds.  In this case, the stem cells are especially good at water absorption and retention

Where the species lives, there are very distinct wet and dry seasons.  From June to September, it rains nearly every day, with monthly averages of nearly 16 inches.  From October to April or May, however, things are different, including the four months from November to February when there is virtually no rainfall at all.

There is an informal agreement among grass taxonomists that it is bad form to name new species until fertile specimens with flowers have been collected and studied.  This species, however, is an obvious candidate for making an exception to the rule, for a couple of reasons.  First, it is so unusual that there seems no question that it is new and different.  Its morphology, anatomy, and DNA all point to species status.  And second, flowering cycles for woody bamboos can vary from a couple of years to decades. And, for a few species, flowering has never been observed at all.  So, it makes sense to make this remarkable discovery official rather than waiting for what could literally be forever to announce that bamboos have now joined the ranks of the succulents.

So, if you want to mess with the horticulturist at your garden center, tell him you’re looking for a succulent.  And after he shows you his burro’s tails, Aloe vera, and a variety of Sedum, say you really had something taller in mind, a bamboo perhaps.  Then, stand back, watch, and enjoy.

Laobambos calcareus. (A) Adult plant in habitat at the type locality during rainy season; (B) detail of foliage leaves; (C) detail of the waxy marks on fresh inflated culms, revealing the ridges present on the dried-state culm during the dormant period; (D) detail of a node and a branch complement; (E) view of base of the clump showing the greenish inflated fresh live culms, along with ridged dehydrated brown dead culms. (Photo credit: Thomas Haevermans 05/2012).

Acknowledgement. I thank Dr. Thomas Haevermans for his permission to reproduce his photographs of the new species.

Further Reading

Haevermans, Thomas, Mantuano, Dulce, Zhou, Meng-Yuan, Lamxay, Vichith, Haevermans, Agathe, Blanc, Patrick, and De-Zhu Li (2020) Discovery of the first succulent bamboo (Poaceae, Bambusoideae) in a new genus from Laos’ karst areas, with a unique adaptation to seasonal drought.  PhytoKeys 156: 125-137.