Yesterday John and George joined a nature walk led by State Park Volunteer Jay Barnhart in Sebastian Inlet State Park near Vero Beach, enjoying a coastal hammock-dune-marsh with gnarly ancient Live Oaks and postcard views to the sea. You learn something every day. Yesterday we learned how the leaves of Cherrylaurel (Prunus caroliniana) snap audibly when creased, and then smell like almonds. And we learned pig farmers use the forked bases of Cabbage Palm petioles as reverse shoehorns for removing smelly boots (like a claw hammer pulling a nail).
Among the botanical attractions were Saltbushes, species of Baccharis. Within our botanical radius are three Baccharis species: B. halimifolia with flower heads in loose clusters, B. glomeruliflora with the heads in compact clusters, and B. angustifolia with distinctively narrow and non-toothed leaves. Baccharis species have a confusing array of English names. And to complicate classification, some of the species hybridize. It is not a goal at this moment to sort out the variations and names. We’ll be generic today.
Unless you see the parachute-fruits, it might be tough to recognize Salt Bushes as members of the Aster Family. After all, how many woody Asters do you see in Florida? (Answer: not many.) The little white unisexual flowers are clustered in un-showy flower heads. The female flowers transform into parachuted fruits resembling those of dandelions or thistles.
Salt Bushes are standard green companions in everyday Florida botanizing, although their vulgarity is a mixed blessing. Despite being native, the shrubs have weedy ways, to the point of being invasive exotics in continents where they don’t belong. And they can be replacement plants here in Florida as natural marshes are drained and altered. Like good weeds, Salt Bushes produce massive masses of wind-dispersed happy-to-germinate seeds. Oddly for weeds, the seedling growth can be shade tolerant. Depending on the species, they tolerate also awful soils, varied water regimes, salt, and abuse. The plants contain heart poisons, so livestock leave them alone, or else! After a fire in some habitats, hello Salt Bushes. Being easy to grow (!) and good looking, Baccharis species have a small market for cultivation.
Baccharis halimifolia is one of those hot-climate to north-woods species distributed from Nova Scotia to Alaska to Florida to Mexico. In Europe, New Zealand, and Australia it is an invader. And the invasion events present a head-scratcher Emily Dickinson would have understood, in her words:
To make a prairie it takes a clover
And one bee.
One clover, and a bee, and reverie.
Now let’s extend that to Salt Bush. They come as separate male and female plants, so to make a prairie on foreign continents it takes TWO Salt Bushes, not to mention lots of bees (of the right kinds). How does a species that needs a male plant to pollinate the female manage to arrive in Australia as a legally married couple to begin the invasion? How do female plants Salt Bushes in a Florida roadside ditch manage a huge fruit-set, and seeds with high germination rates? (I am not certain that occurs but informal observation seems to indicate it does.) Such saturation-pollination would require a lot of bees and even more reverie . Every one of those millions of parachute fruits on a single female Salt Bush would require its own pollination event. Inquiring minds want to know, how can it bee?
Splitting a species into separate males and females is one step in evolution, but another step is then possible to compensate for iffy pollination, a “plan B” to make seeds without benefit of those male plants and super-bees. Such seeds are clones of the mother plant, and are called apomictic seeds (ap-oh-MICK-tic). Is that true of Baccharis halimifolia? Probably, but if it has been shown experimentally I’m not aware of it. (Always a big possibility!) Apomixis has been demonstrated in different Baccharis species. It would be interesting to isolate a female Baccharis halimifolia from all possible outside pollination and see if the usual bazillion fertile fruits form.