Over the last 10 years I've noticed Acacia Mearnsii, or black acacia trees coming up all over the east bay and in my back yard. This tree grows extremely fast and is very hard to eliminate once it's roots are established. The roots on this tree grow laterally, and sprout aggressively especially when the tree feels threatened.
There are 800 different cultivars of Acacia. They have a short life span of 15-30 years which explains their fast growth habit and are messy buggers. Two extremely large and well established black acacias have fallen over in my back yard, perhaps it was their old age I really don't know why. Within 2 weeks of falling, 10's of small sprouts pop up all down the length of the roots. If left alone, these small sprouts will be small trees in a matter of months and a grove in a couple of years.
Another issue with this tree, is growing anything under their canopy, really within the whole back yard is not easy. Even the most tolerant of plants simply don't thrive. The tree takes up water with it's tremendous web of shallow lateral roots, so other plants can't access it. It also binds the nitrogen in the soil making it unavailable to plants. Plants always struggle to live.
The soil also has a distinctive smell. A smell I only notice when black Acacia trees are present. The soil is arid, lacking in organic matter and cannot uptake water easily no matter how much I amend it.
The small leaves and seed pods are a mess and a fire hazard. If a black acacia catches on fire, the wood is so dense, the fire would be an extremely hot and dangerous one.
I'm not normally so anti-tree of any type. So here are a couple of positives;
~The wood of the black acacia is desirable for furniture, flooring, musical instruments, etc.
~In the savannah of Africa, they're a lovely shade tree for animals.
~Some consider the flowers beautiful. If you have allergies, that's debatable.
I find this tree to be a nuisance, and at the moment, its my own personal quest to demolish. People don't realize the problems it can cause until the tree is enormous and by this time, it's a huge expense to deal with. I believe the tree is native to Australia, not here.
I'm thankful that the city of Berkeley has labeled the black acacia a problem and is working to remove it from the hills over time. Its not surprising how the citizens of Berkeley are putting up a fight, I mean it is a tree and it's growing well, but come on, it's not even a pretty tree! Protecting the black acacia is a disappointing opinion considering all the above mentioned issues, plus the acacia is also highly flammable.
The organization cal-IPC, California Invasive Plant Council have this cultivar on their list of invasive plants. A. mearnsii is regarded as an environmental weed in many parts of the world. It has been nominated as among 100 of the "World's Worst" invaders by the IUCN Invasive Species Specialist Group and it has been listed as a noxious weed in Hawaii and as a Category 2 invader in South Africa (invaders with certain qualities, e.g. commercial use or for woodlots, animal fodder, soil stabilization, etc. These plants are allowed in certain areas under controlled conditions).
The organization cal-IPC, California Invasive Plant Council have this cultivar on their list of invasive plants. A. mearnsii is regarded as an environmental weed in many parts of the world. It has been nominated as among 100 of the "World's Worst" invaders by the IUCN Invasive Species Specialist Group and it has been listed as a noxious weed in Hawaii and as a Category 2 invader in South Africa (invaders with certain qualities, e.g. commercial use or for woodlots, animal fodder, soil stabilization, etc. These plants are allowed in certain areas under controlled conditions).
If you have a black acacia sprouts on your property, please pull it asap. The next time you turn around to check up on it, it will already be a problem.
