A touchy subject
Spiny, scaly and hairy plants that add texture and interest to the garden
Hairy leaves and prickly stems can be irritating at best, painful in the extreme. Sometimes, as with roses in our garden, we tolerate the thorns for the beauty that emerges from within. In nature, a plant’s soft or bristly overcoat is an important adaptation to where it lives.
The woolliest of plants live in deserts, hot or cold, which tells you a lot about why they have hairs. The shaggy coat is there mostly to protect the plant from excessive sunlight or from losing too much water, but it also provides a shield from frosts, drying winds and sometimes the munching of predatory insects.
My favourite hairy plant is a daisy called Coespeletia palustris. Botanists discovered this species a few years ago, in swamps high up in the Venezuelan Andes. They described it as having “Dr Seuss-esque insulation”, perhaps like the truffula tree in The Lorax. In fact, it belongs to a group of daisies, the subtribe Espeletiinae, considered by some to be the hairiest of all plants – the Costas of the plant world?
This species is described as lanose, which means the plants are woolly, with long, soft, tangled hairs, like a sheep. This is not to be confused with floccose, which means these hairs are easily rubbed off.
Botanists get a little obsessed with the nomenclature of hairiness, devising precise terms to describe the shape, number and texture of hairs. You can probably imagine bulbous (swollen) or plumose (feathery) hairs, but what about those that are peltate (shield-like, on a central stalk, like an umbrella) or strigose (sharp, stiff, and bent over close to the surface)?
Some terms are helpfully evocative, such as arachnoid for cobwebby hairs. Others are less intuitive, such as furfuraceous for a plant covered with soft, easily displaced scales (flat hairs), which you might also call scurfy. Or roridous for a covering of small, transparent appendages giving the overall appearance of dewdrops.
Old man cactus (Cephalocereus senilis) from eastern Mexico is possibly the most famously hirsute plant. In the hot desert, the sometimes 30cm-long bristles provide shade and insulation, perhaps even capturing moisture from fog and dew. In cultivation, the silvery mop provides a conversation piece, particularly when sporting sunglasses.
The bristles of old man cactus are modified spines rather than true hairs, and they supplement a set of the more usual cactus armoury – in this case, clusters of sharp yellow spines. While cacti are also candidates for the Costa award, they sometimes make do with a cloak-like covering of sharp spines.
Teddy-bear cholla (Cylindropuntia bigelovii syn. Opuntia bigelovii) is such a plant. The ‘fur’ of this deceivingly cute cactus from Mexico and southern US is a mesh of spines. Like all cacti, the spines are modified leaves, and the fat green blades are stems.
I’ve had one close encounter with this species, in Joshua Tree National Park in Southern California. There were ‘touch at your own peril’ signs and the alternative common name, jumping cholla, to consider. Of course, I picked up a fragment, just to check, before inelegantly flicking it
between hand and foot. I was extracting the embedded spines for days.
In this case, the plant’s adornment has the additional role of helping it to get around. Detached segments of the cactus ‘stick’ to passing animals, such as me, which allows them to be carried to new homes, where they can take root.
Here in Australia, our flora isn’t quite as aggressive, although there are plenty of seeds with barbed or sticky (glandular) hairs waiting to be transported to new places. There are some aggressive-looking bush tomatoes, such as the poisonous Solanum quadriloculatum, which has purple pubescent stems punctured by 5mm-long prickles. This plant’s leaves, however, are carpeted only in beautiful soft, star-shaped (stellate) hairs.
We do have plants with hairs that sting, such as common nettle (Urtica spp.), or Gympie-Gympie stinging tree (Dendrocnide moroides) from Queensland. Both have fragile silicon tips that become embedded in our flesh, injecting toxins with effects that range from irritating to excruciating.
Mostly, indumentum (hairiness found on the outside of plants) is harmless to us, and quite attractive. Indeed, hairy and ornamented plants can add distinctive textures to your garden. You could use cacti and succulents for an architectural statement, or perhaps plant a ‘grey garden’ using woolly-leafed and felted plants such as verbascum, lamb’s ears (Stachys byzantina) or some of the sages. And if you want to plant Australian natives, consider Pomaderris spp. or blanket leaf (Bedfordia arborescens).
Alternatively, create a ‘sensory garden’, playing on the many textures available with these plants, as well as their perfumes and colours. My only additional advice is to avoid cholla and stinging trees, at least near the front of the garden bed.