The definition of serotinous is
“late blooming,” as in Prunus Serotina,
the wild cherry tree which flowers later
than its relatives. In the column on
self-immolation of plants, Cecil
thinks the word has something to do with fire.

Welcome to the SDMB, **jjaandi **. You’ll have fun here. By the way you don’t need to hit return in the reply box - the lines wrap themselves. A link to column being discussed is useful: Is there a bush that spontaneously bursts into flame to reproduce? agrees with you, but the OED says (and I’m confident that specialist botanist dictionaries would too) that the word can be used in the sense that Cecil does:

So germination by fire is a special case of serotiny, and perhaps the use of the words “that is” in the column is a trifle misleading.

Which brings me to a more burning question. Is all serotiny a response to heat, or do some plants postpone devlopment due to hours of sunlight or some other factors? (I’m not a botanist.) The “late pear,” Pyrus serotina, actually flowers in March (early) and bears ripe fruit in November (late).

Merriam-Webster’s considers the late-opening definition to be the primary (in fact the only) one:

The basic sense is simply “late opening,” and thus can apply both to flowers that open late in the season, as well as cones that open long after their fertilization. However, the most frequent use botanically is probably in reference to cones.

To answer jjaandi, timing of blooming and fruit maturation is often determined by changing day length, but also can be due to temperature or rainfall.

Serotinous cones of course are a different situation, since they are usually an adaptation to fire.

A search for the string “serotin” at the USDA site (great site) yields some 25 species or subspecies which are named for a “late” characteristic. Among them are certain cherries, pears, elms, poplars, grasses, sedges, and daisies. And one coniferous plant, “Pinus serotina.”

The Banksia trees of Australia will only drop their seed after the seed pods have been seared by fire. They are serotinous. .
If you pry open the seed pods and plant the seeds, the only way you can make them germinate is to water them with water that has had smoke bubbled through it (maybe bong-water is good for this - dunno, I haven’t tried it).

Speaking with reference to the use of the term as an English adjective, and not as part of a scientific name, I’ve studied quite a bit of botany, and the only sense I have ever seen “serotinous” used is with reference to pine cones, specifically ones that only open in response to fire. While the term may sometimes be used (as an English adjective) for late-blooming species, by far the most common usage is the sense in which Cecil used it.