Against the odds: Mimosa
Gardening is often about taking risks and gambling on what will grow. Personally I dislike gambling. But I am always willing to try a plant that is a bit risky, if I like it. So it was with expectations that I might fail that I planted a mimosa (Acacia dealbata) in the garden early on. It was planted in the ‘lemon meringue’ garden, on the south side, which was a bit daft really. Most of the plants here will be in flower in summer and a froth of powdery scented, fluffy yellow bobbles in March was not really going to add much. LOL. Did I say a froth of flowers?
I knew it was a risk because this is not a very hardy tree. But despite this, all garden ccntres here sell young plants. They tend to be small, hard-pruned plants, often in bud, or lanky, single stems tied to 2m canes. It was four years ago that I planted my small plant, when the beds were barely cut out and the soil was not very improved. But despite my expectations, it grew like crazy. It is the tallest tree in the garden with a single trunk about 1.5m high and then branching, in a rather ungainly way.
For the past two years it has set flower buds in autumn, which is tantalising. But it is windy here and can be cold in winter and every year the leaves get blown off (it is evergreen) and the flower buds all drop off by spring. I was convinced that the same had happened this year. And then, braving the garden yesterday, I noticed a few, primrose yellow spots in the otherwise bare branches. And lo, there were flowers.
Now it is not exactly a ‘display’ but it does give me hope. Not directly related, I have noticed a young plant coming up in the rose bed, to the south. This mystifies me because I was not expecting it to sucker and there is no way it can be a seedling, since I have never even had flowers before. Strange.
Anyway, for now I will marvel at my little patches of yellow and be thankful that March was mild and wet and not frosty. That must be the reason I managed a few flowers. And it just shows that it pays to take a gamble sometimes.
The Biking Gardener 
I love mimosa, it’s so pretty…
it is – even if you only get a straggly bit!
It’s a start…
OH MY! This might be one of the two most aggressively invasive naturalized exotic species here. Broom might be comparable, although not as voluminous. Even young seedlings are very difficult to kill. They can regrow from small bits of roots. . . . However, I do happen to enjoy the bloom. It reminds me of other species of Acacia that were more popular where I went to school in San Luis Obispo. The sucker might be a response to the harsher climate there. Young and vigorous trees should not sucker, but deteriorating older trees do. Strangely, suckers do not respond well to transplant. If it is in a situation from which it must be removed, it will likely recover slowly from the process, and regenerate a new stem from its roots as the original dies back. However, it will forget all about the trauma by the following season! As the tree matures, I would recommend collecting some of the seed, or perhaps retaining a few seedlings that grow in the garden, to replace it. Such trees grow fast, but may not last for long. Some of the oldest trees here might be about twenty or thirty years old, but perform best before they get to be about half as old. They get to be about forty or fifty years old where they grow a bit slower in warmer and drier climates, such as the Santa Clara Valley. I can not predict how it will perform in your climate. It could perform very well for only about ten to fifteen years, as it does here, before succumbing to the climate, or it could perform well for much longer by growing slower within the particular climate. Healthy trees are typically lanky while young. They are awkward to prune also. Limbs sag as they get heavy, but are likely to die completely back to the main trunk if only partially pruned back. Trees tend to lean from their own weight. The healthiest specimens commonly fall over from the weight of their new growth and bloom. Even if your particular specimen does not exhibit weedy growth like it does here, it might get somewhat heavy between spring and summer. It is gratifying to know that this locally undesirable but otherwise spectacular species is appreciated in some gardens.
Thanks for your comments. I know that acacias can be a weed in many warmer climates. This one is often grown as a wall shrub here but does well in urban gardens and by the coast. I was surprised that it has done so (comparatively) well here. It is lanky and, as you say, can be tricky to prune and does die back if not done carefully. If it lives to 50 years then I won’t complain, or see it! It is usually fully recovered from wind by late summer and looks in great health but cold and wind strips it over winter so that it looks its worst at this time.
Wall shrub?! Is that like a shorn hedge? I would not expect it to respond favorably to shearing or pruning from such form.
a wall shrub is a shrub grown in two dimensions against a wall rather like a climber, to protect it from cold or to gain the reflected heat of the wall – we grow ceanothus like that here!
So, it is like a hedge against a wall, or a free standing espalier. Bougainvillea perform quite nicely here, but actually perform even better on a warm wall with a southern to western exposure. The do not need protection from frost, but enjoy extra warmth.
We ever had only one in the garden, suckered everywhere before being killed by that hard winter, 2010 or so, but the suckers continued for another few years until we finally got rid of them.