New thug in town - Dittrichia graveolens. How to get rid of it. And how to tell it from native Madia
|Young Dittrichia graveolens, stinkwort, showing "Christmas tree" form|
The content below pulls together two articles from the upcoming newsletter, text reused with permission, photos used with permission too. (Nice thing about the blog -- more room for photos.) It's good to spread the word widely about this widely spreading weed.
Wanted Dead or ... ... DEAD!
DITTRICHIA GRAVEOLENS, a.k.a. stinkwort, is a new invasive non-native plant to watch out for, first recorded in the early 1980s in Santa Clara County. It is a late-summer to fall annual that germinates over a prolonged period from May to September, putting it out of sync with the seasonal development—and control methods—of other non-native warm season annuals in the Asteraceae family. It has a heavy camphor smell - unmistakeable, and touching the sticky leaves can cause dermatitis in some, similar to poison oak rash (but not, in my experience, in very many people).
|Last year's skeleton still shows the "Christmas tree" shape. Surrounded by seedlings.|
At maturity, the plant is often the shape of a perfect Christmas tree. The tiny dandelion-like flowers are yellow and have ray and disc petals.
OCTOBER UPDATE: with more experience I now know that the below picture is of other seeds sticking to the stinkwort plant - which is very sticky. In fact one way to find it after thistles have gone to seed, is to look for the plant covered in thistle down.
|Stinkwort seeds have seeds with hairs - but above is thistle down sticking to a stinkwort plant! |
Photo credit: Toni Corelli
|Stinkwort flowers gone to seed - maybe half an inch across or less|
|Buds, flowers, foliage of stinkwort. Once it flowers you can't leave the plant lying where you pull it.|
Photo credit: Toni Corelli
In small infestations the best method of control is hand pulling the young plants, preferably before they start flowering. If plants of Dittrichia are pulled when in flower they will continue to ripen seed even after they’re uprooted, so they should be bagged and disposed of and not left on the ground.
Uncontrolled, Dittrichia can convert large swaths of land to worthless monocultures.
OCTOBER UPDATE: To dispose of plants that have flowered, bag them, add a little water, seal the bags, and leave them rot. It is not clear how long you have to leave the bags. Up to a year perhaps. For large infestations the best you can do (after plants flower) is pile them up in a shady location out of the wind, where the spread is minimized, possibly covering with a tarp. The very best you can do is not let them go to seed next year. Seed life is probably three years though I recently heard it might be only two years - which is good news.
Click here to view the California Invasive Plant Council page on stinkwort, Dittrichia graveolens.
Click here to view a wonderful poster on this scourge, from the Cal-IPC site.
Click here to view my Sentinel article on stinkwort.
|Madia elegans with (closed flowers of) Clarkia rubicunda in my garden. Both are local wild natives where I live.|
|Woodland madia, Anisocarpus madioides. Photo credit: Pete Veilleux, East Bay Wilds|
Madias range in size from about six inches up to six feet tall. Their foliage is heavily glandular (sticky!) with a sweet fragrance. The flowers are yellow, with disc and ray flowers. Madia elegans flowers are showy and can have brown in the disc and base of the ray petals. Flowers range in size from small to large and showy.
|These tiny flowers sit atop a large plant! Madia sativa, coast tarweed.|
So - Weed early and weed often!
|Lovely blossom of Madia elegans -- to end on an upbeat!|