Friday, 5 August 2011

Rue the day

There are a quite a few plants called something-rue or something-bane in English.  I’m thinking of fleabane, wolf’s bane, goat’s rue, and rue.  They all suggest plants that are toxic or at least repellant, plants you'd rue, or regret, eating or touching.  I’ve seen rue (Ruta graveolens) a couple of times in the Mediterranean, usually near the coast, like this plant on the Cinque Terre trail in Liguria, Italy.
So, it was a nice surprise to see a row of rue on a roadside berm in Northland (suburb), Wellington last week.  It was planted to surround a patch of angelica (Angelica pachycarpa, not the culinary A. archangelica), maybe to keep cats and dogs away.  It’s pretty stinky stuff and the smell takes a while to wash off the hands.
Ruta graveolens, Northland, Wellington 2011.

The genus Ruta gives its name to the family Rutaceae, which includes citrus and many other plants.  Rue has traditional  medicinal uses, and can cause dermatitis.
Phebalium squameum (satinwood) is another member of the Rutaceae. The best examples I know are specimen trees in the Wellington Botanic Gardens, but usually in Wellington it's a hedge plant. It has a peppery smell and little starry white flowers. The wood is especially interesting. First, it's pale or yellowish, although often affected by boring insects and rotting of the heart wood. Secondly, it burns well because of the volatile oils that are common in the family Rutaceae (squeeze oil out of a lemon or orange peel next to a lighted match to see what I mean; video here). Thirdly, it can cause a pretty severe contact dermatitis in susceptible people. I first got this as an 8 year old when we planted a Phebalium hedge all round our section in Tawa, and it came back a few years ago when I cut up some logs for firewood. 
Satinwood trees in the Wellington Botanic Gardens.

Satinwood is an Australian tree; they have a lot of Rutaceae there, but we have only three native species.  A colleague reported getting a rash from the native mairehau, Leionema nudum.   She described blisters on her nose, fingers, and arms that lasted for weeks after she crushed and sniffed some mairehau leaves in Northland (district), where it grows.
Satinwood leaves.

It seems sunshine and moisture (sweat or water) make the dermatis worse; it’s a photosensitive dermatitis.  Grasses, parsnip tops, and especially Heracleum can also cause photosensitive dermatitis. I remember my Mum got photosensitive dermatitis on her face from using an all natural organic herbal soap. And here are my legs after tramping through long grass in flower on a sunny day in the Takitimu Range (Southland) a few years ago.  

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