More Weeds That Deer Don’t Eat

4 September 2024

Last weekend I noticed this group of tall plants in Schenley Park with a distinctly Christmas tree shape, shown above. They are not beautiful, they are certainly weeds, and they are thriving in a place where deer have eaten all the non-poisonous native plants. These are either poisonous or unpalatable.

I took a closeup of the leaves and asked Picture This to identify it: Sweet wormwood (Artemisia annua), native to temperate Asia.

Plants in the Artemisia genus taste bitter and their crushed foliage and stems have a strong smell. Deer find it extremely unpalatable and can tell from far away that it smells too ugly to approach.

Plants in the Artemisia genus often have medicinal properties. Sweet wormwood (A. annua) contains artemisinin which was discovered in 1972 and is used to treat malaria. Unfortunately the malarial parasite in Southeast Asia has developed artemisinin resistance so the drug can no longer be used alone to cure the disease.

Sweet wormwood’s close relative common mugwort (Artemisia vulgaris) also has a wide range of supposed pharmacological uses. These uses probably account for the plant’s presence in North America. The Pittsburgh area has plenty of it!

Another reason why sweet wormwood, in particular, may be thriving this year is that mature plants are fairly drought resistant — and we are in a drought.

Drought and deer this summer have combined to leave Pittsburgh with so many weeds.