Considering Weeds

I like plants. I have a yard and garden. This week, weeding, I contemplated weeds. What exactly are they?

"Weed" is a wonderful concept. It is totally human; a weed is a plant that interferes with human activity, which can be reduced to "a plant in the wrong place." I checked the American Weed Science Society's website--they dedicate their careers to controlling weeds, so need a good working definition--and that website defines a weed as "a plant that causes economic losses or ecological damage, creates health problems for humans or animals, or is undesirable where it is growing." 

Tree Cholla, Extrafloral Nectaries, and Ants

Visiting New Mexico, you can't miss the big cacti. Prickly pears stand two to three feet tall, not hugging the ground like the ones in Colorado. Chollas can be more than eight feet tall.

In July, the tree cholla (Cylindropuntia imbricata) was flower.  With deep rose-purple flowers, it was doubly noticeable. 

tree cholla, Cylindopuntia imbricata, in flower

Camouflage in Plain Sight

I taught ecology for years. The text books feature dramatic examples of ecological principles--camouflage illustrated with a big green katydids shaped like a leaf, mimicry illustrated by a nonvenomous snake banded like a coral snake, or an example of mutualism with an orchid and exotic bee--almost always tropical. Which tended to make you think that to see biology you should go to the tropics. In fact, though, those basic principles--camouflage, mimicry, mutualism--and all the other pillars of ecology--predation, parasitism, competition--are everywhere. 

Plant Story--Glorious Goldenrod

As the summer winds down, splashes of gold appear on the roadsides and in the prairies and meadows: goldenrod! Depending on where you are, you see a different group of goldenrod species, but they are found all across North America. In fact, goldenrods are a predominantly North American group; there are about 100 species, of which 77 are native to North America, 8 to Mexico, 4 to South America, and 6 to 10 to Eurasia.