Why Locust Trees?

What is it?

Robinia pseudoacacia, commonly known as Black Locust, is a medium-sized deciduous tree native to the southeastern United States. 

Why were they chosen?
Black Locust is a fast growing, low-water tree with pretty blooms in early summer. The trees have historical significance in Mill Valley - Locust Avenue was named for the tree and has a few remaining very old trees – a part of Mill Valley’s history.

Are they invasive?

California has multiple climates and subclimates. There are lots of species that are invasive in southern California or the Sierra Mountains that are not invasive here. 

Black Locust trees are included on a list of California invasive plants put out by the California Invasive Plant Council (Cal IPC), however, it is said to be a stable species and not spreading. The ecological impacts of these trees are minor on a statewide level due to their reproductive biology and other attributes which result in low to moderate rates of invasiveness. 

How will the City control them?
Black Locusts spread primarily by means of root suckers, not seeds. The Black Locusts will be planted in a median, so their growth will be confined. Work crews will control root suckers by pruning, and herbicide is not necessary.