Plant 199

Ruscus aculeatus L. (Asparagaceae)


Butcher's broom

Butcher's broom is a monocotyledon of a most curious appearance. It is a multi-stemmed, evergreen shrub that rarely gets taller than one metre high, and appears to be covered in stiff, spiny leaf-like structures. However, closer examination shows that these structures cannot be true leaves; they sometimes bear tiny flowers, followed by spherical, bright-red, fleshy fruits, on their upper surfaces. The green structures are cladodes. Evolutionarily, cladodes are flattened stems that perform the same photosynthetic function as leaves. The true leaves are reduced to tiny, non-photosynthetic, papery scales associated with the flowers and the bases of the cladodes.

Butcher's broom is native to southern England, and is the only British monocotyledonous shrub. It is slow growing and shade tolerant, and occurs naturally in dry, shaded woods and hedgerows. Outside of the Britain, is distributed north around the Mediterranean as far as northern France, Italy and Hungary, with scattered populations in North Africa. The species' western limit is the Azores, whilst it extends through Turkey in the east.

Unusually for a stem-photosynthetic plant, butcher's broom is highly shade tolerant and drought resistant with low transpiration rates and water storage in the cladodes. Stem-photosynthetic plants are usually associated with arid, high-light environments.

Butcher's broom is dioecious, it has separate male and female plants with insect-pollinated flowers, apparently offering pollen as a reward. However, there is little direct evidence for either insects or wind having a role in pollen movement; this might explain the low levels of fruit and seed production found in natural populations. In addition, there is poor fruit dispersal despite the fruits having clear adaptations for bird and mammal dispersal. One idea to unite these apparent contradictions is that butcher's broom is a relic of the tropical forests that covered parts of Europe during the Tertiary (2.58-65 million years ago). The ecological success of butcher's broom populations today appears to be a consequence of vegetative reproduction. The plant has a deep, stout rhizome (horizontal underground stem) system.

The generic name derives from the Latin for a butcher's broom, ruscum; this plant has traditionally been used for cleaning butcher's chopping blocks. The specific epithet, aculeatus, is a reference to the plant's spines. In antiquity, the plant had few medicinal uses, despite butcher's broom containing a rich cocktail of steroidal saponins. These have been shown to have a wide range of potent medicinal effects; wild-collected material is particularly rich in these compounds.

Further reading

Thomas PA and Mukassabi TA 2014. Biological Flora of the British Isles: Ruscus aculeatus. Journal of Ecology 102: 1083-1100.

Stephen Harris