Tansy (tanacetum vulgare) is a perennial herb that has a number of uses in desert gardens.
Tansy foliage is feathery and a beautiful bright green. The flowers of tansy are yellow, clustered and button like. The stem is leafy and stands erect and it may grow up to three feet high. It has an interesting aroma, which seems to be a cross between rosemary and camphor. The plant is very aggressive and, if left unguarded, will invade beds.
I find that the most attractive element of the plant, besides the attractive foliage is that it seems to repel insects, particularly flies and mosquitoes. I know that it may be odd to think of mosquitoes in the desert, but they do exist, and can breed in rain barrels, cisterns, or other places where water is still.
I have tansy planted near outside garbage cans, and near some home entryways, and it seems to work. Many herbalists swear that a tea made from tansy and sprayed onto pets will repel fleas and ticks.
Tansy is sometimes difficult to find in nurseries, perhaps because it is sometimes confused with two noxious weeds that have tansy as part of their common name and have invaded the arid southwestern U.S.: tansy ragwort (Seneca Jacobean) and tansy mustard (Desaurainia pinnata).
Cultivation
Tansy will not only survive, but it will thrive in just about any soil, even poor soils, and does extremely well in sandy desert soil. It will survive cold down to USDA Zone 4, so it can be planted in a wide range of desert areas, from hot lowland deserts to arid high plains.
Tansy likes sun, but it will also do well in partial shade. I have some growing under a maple tree, and it is extremely vigorous. It is semi-drought-tolerant, so you might want to water them once a week during really dry periods.
Fall is actually one of the times to plant (and/or divide) tansy. It you are lucky enough to find tansy, you can divide it by slips or by dividing the roots. Whichever way you decide, plant them at least a foot apart. You should probably add a general-use fertilizer when planting.
You can plant tansy in the spring from either division or from seed.
Origins of the Name
Some plant historians believe that the name is derived from the Greek word athanaton, which means immortal. It is said to be the herb given to Ganymede to guarantee him immortality.
In the Middle Ages, tansy cakes were eaten by Christians on Easter Day, in remembrance of the bitter herbs eaten by the Jews at Passover.
Regardless of the practice, it has been reported that eating of tansy (and tansy extracts) has caused internal poisoning, severe gastritis, violent spasms and, in some cases, ingested tansy tea has been reported to have been fatal. I would strongly discourage ingesting it.
There also may an allergic reaction to the plant, which is displayed by allergic dermatitis.
