The Aster Family (part one)

From golden ragwort in April to goldentop in October, about one in five flowering plant species that I find in the Maryland Piedmont is in the aster family.

It’s unknown how many plant species there are altogether: discoveries still happen, and of course there’s taxonomic uncertainty. But experts believe that there are about 352,000 flowering plant species (angiosperms), and of the other major plant groups, there are an estimated 1,000 species of conifers and conifer allies (gymnosperms), 13,000 species of ferns and fern allies (pteridophytes), and 20,000 species of mosses and liverworts (bryophytes). [The Plant List]. So it’s probably safe to say that flowering plant species outnumber all other plant species combined by an order of magnitude.

Of the flowering plant families, the Asteraceae is probably the largest with about 23,600 species in 1,620 genera. [Encyclopedia of Life]  Whether or not it actually is the largest depends on the current state of taxonomic science; the other contender is the Orchidaceae.

There are 2,401 native Asteraceae species in North America. [BONAP] The Maryland Biodiversity Project lists 373 Asteraceae species (native and alien) in Maryland, and by my very rough estimate, about half of these can be found in the Piedmont.

So what are the characteristics of aster family flowers?  Have a look at this Jerusalem artichoke:


How many flowers do you see? If I zoom in I can see about 21, not counting the unopened buds.

Wondering how that can be? Here’s a clue: an older but still accepted name for this family is Compositae, or composites. Plants in this family bear heads that appear to be single flowers, but these heads comprise from several dozen to several hundred individual flowers.

next time: aster family floral morphology

This post is dedicated to my friends Cheryl and Barry, who independent of each other gave me the idea to write about plant families during the dormant season. 

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