Saturday, February 27, 2010

Butcher’s Broom: Ruscus aculeatus

Ruscus aculeatus, or Butcher’s Broom, isn’t exactly the showiest plant in the Mediterranean plant collection here at the UConn greenhouses, but it frequently attracts the attention of more observant visitors. Ruscus looks a little like a grayish, knee-high holly bush from a distance, but when examined closely it reveals a puzzling characteristic: its tiny, green flowers and marble-sized red fruits emerge from the middle of what look like its leaves. Normally, we think of flowers growing at the end of stems. Botanical science confirms common impressions about plant morphology in this case; developmentally, it would be just about impossible for a flower to grow directly from a leaf.

The mystery of flower-bearing leaves in Butcher’s Broom is solved when we consider the possibility that those pointy, flat greenish appendages might not be real leaves at all. Indeed, the evidence from detailed study of the position and development of leafy structures in Ruscus indicates that they are really cladodes (sometimes called phylloclades), or flattened, green, leaf-like shoots. The real leaves of Ruscus are reduced to tiny, scale-like remnants, sometimes visible at the base of the cladodes in young shoots. So, Ruscus flowers are borne on stems, just like in any other plant, but the stems have a very unusual form.

Of the half dozen species of Ruscus, R. aculeatus seems to have the spikiest, thickest “leaves,” and is generally the most suitable for growing in collections of succulent plants. It can take soil that dries out completely between waterings, but is also surprisingly tolerant of low light levels. As a houseplant, Ruscus isn’t quite as unkillable as its distant relatives the Snake Plants (Sansevieria), but it still requires persistence and special effort to actually snuff one. Butcher’s Broom can take all sorts of temperature regimes, but does best with cool winters. Growth is always very slow, but a healthy plant will flower and send up new branches from its underground rhizomes when the days are short.

Ruscus aculeatus is not especially common in cultivation, but a few mail order nurseries (such as Plant Delights in North Carolina) do offer it. Florists use other species of Ruscus as “foliage” in arrangements, dry or fresh, though the cut stems can’t be used to start new plants, since they do not root. For those with a truly black thumb, florists sometimes stock fake silk and plastic Ruscus.