Baccharis glomeruliflora and related species

Asteraceae, Aster Family

Driving home yesterday from working with John on our soon-to-be-printed photo guidebooklet to trees and shrubs (hint hint), I spotted an old favorite tree coming into bud, again.  How did another year go around?  Saltbushes are odd and pretty.  Stopped the car and took a couple photos.

Not sure if the tops were burned, pruned, or neither.

The Aster Family is huge, with thousands of species, almost all of them herbaceous.   Among the exceptions is the genus Baccharis, the 400 species of saltbushes.  Funny how a family that is nearly herbaceous, when it makes a tree that tree remains partly herbaceous.   Our local Baccharis glomeruliflora has a thick woody base and meaty lower branches, and yet “annual” upper branches, perfect for replacement after fires, storms, droughts, and basic bad experiences.

Those throwaway branches perhaps play a part in the attractive spacing of some Baccharis stands.  The plants shower the ground with millions of seeds, yet the mature bushes practice polite social distancing.   Wonder how and why?

Turns out Baccharis  is a wicked poisoner of surrounding vegetation.   Studies by ecologist Francisco Ibanez, who made the graph below,  and others have shown massive reductions in the growth of test plants, sometimes over 90% reduction.  Baccharis clobbers them.  Hey, saltbush acts like biblical sowing of salt.  The saltbush deposits  persistent oil in the soil that functions as a natural preemergent herbicide. Some researchers even suspect Baccharis to “gas” its victims.  Betcha the parent plant suppresses crowding by its own babies, perhaps by dropping those disposable branches around its own feet, or their foliage, or their poison drippings.   After all, in the plant world, who are your worst competitors?  Answer: the apples not falling far from the tree.  It is not nice, but multiple species of plants practice “autotoxicity” —we would call it infanticide. 

Those rising lines show increasing death and destruction with increasing Baccharis exposure. By F. Ibanez