An Excerpt from Jim Conrad's
Naturalist Newsletter

from the December 26, 2010 Newsletter issued from Hacienda Chichen Resort beside Chichén Itzá Ruins, central Yucatán, MÉXICO

Several times we've noted species that begin growing as woody shrubs or trees, then when they get larger start leaning on or scrambling over other vegetation, and end up twining more or less as vines, sometimes herbaceously so. I suspect that this is an adaptation to the region's hurricanes. In our dry, scrubby woods nowadays such a semi-woody bush/vine is bearing white flowers that look familiar to any Northern wildflower fancier who knows the thoroughworts and bonesets -- members of the genus Eupatorium, of the Composite or Sunflower Family. You can see our bush/vine below:


A close-up of several flower heads, each flower with two white, thread-like style-branches emerging, is shown below:

Jack-in-the-Bush, CHROMOLAENA ODORATA, flower heads

A split-open flower head showing slender, white corollas packed side-by-side, each corolla topped with five tiny teeth representing five petals, with the corollas atop their future one-seeded, indehiscent fruits, or "achenes," and very slender, white, hair-like bristles (the "pappus") atop the maturing fruits is below:

Jack-in-the-Bush, CHROMOLAENA ODORATA, flowers

This plant is known by several English names, though none seems commonly used. Jack-in-the-Bush, Fragrant Boneset, Fragrant Mistflower, Siam Weed, Bitter bush, Devilweed... Even the plant's technical binomial is a little tricky because traditionally our plant was placed in the huge genus Eupatorium (over 1200 species), but in the 1970s when King and Robinson split up the genus it became known by the less memorable name CHROMOLAENA ODORATA.

One reason Chromolaena odorata, which is native from Mexico and the Caribbean south to Paraguay and Argentina, bears so many English names is because it's spread as a weed into much of the world's tropics. The accepted view is that the species turned up in Singapore and Malaya in the 1920s via ballast in ships from the West Indies, then spread into much of the rest of Asia. It first appeared in Africa, in Nigeria, in the 1940s, probably via contaminated seeds of a forest tree being introduced from Ceylon, and now inhabits several African countries. In many countries it's become a serious weed.

Here the plant is typical of woods edges and along trails cut through the scrub. It's a native wild plant with a slight tendency toward weediness, but certainly in no place does it "take over" or exclude the rest of the community. It doesn't appear in long-established forest, nor in very recently abandoned fields. It fits into the community of plants and animals typical of a young, semi-weedy forest, maybe one that was a cornfield 20 years ago. As such, you could say that it's well adapted for the slash-and-burn shifting agriculture that for centuries has been practiced here by the Maya.