Yellow mimosa against a clear blue sky
Mimosa is associated with clear blue skies, notably the Cote d'Azur in the south of France, where wealthy people from northern Europe used to enjoy the same benign winter climate that encouraged a great show of this most spectacular tree.
One quite popular kind of mimosa has been flowering since before Christmas. The plant in question is not the true florists' mimosa, which is Acacia dealbata, but a closely related species, Acacia baileyana with more silvery grey-green leaves.
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The latter is smaller, quicker to flower, and hardier, surviving and flowering much further inland, usually given the benefit of a warm, sunny wall, and is known as the Cootamundra wattle. Wattle is a common name used for many species of acacia in its native Australia.
The true mimosa is an unusual tree seen in coastal gardens. If you live near the east coast, you may have noticed the showy yellow flowers of the mimosa but more a few kilometres from the coast, you are unlikely to have seen this tree. In a mild garden, this fine tree can grow to 10 metres or so, its smaller relative about half that height.
The tree would be a beauty if it never flowered, but it does with very showy, delicate, fluffy light yellow sprays. The mimosa generally appears in florists' shops early in the new year. These cut flowers usually originate in southern France and Italy where the weather warms up earlier than here. In fact, this tree has become semi-wild in parts of warm countries owing to their suitable climate conditions.
Being native to Australia, acacia likes mild winters and hot sunny summers. There are a couple of other species that manage to survive and flower here in mild areas, such as Acacia pravissima, with spiky stems, and there are many others not hardy enough. This one is occasionally grown as a conservatory plant and pruned after flowering.
Mimosa is a member of the pea family and, like many members of that family, it likes free-draining soil. It also likes the soil to be reasonably fertile and it will grow at a very rapid rate in the right conditions - as much as a metre a year is possible. It needs good shelter and full sunshine to make that kind of growth and it will also come into flower at a younger age when the growing conditions are good.
If the shelter is not good, the lovely ferny evergreen foliage will be badly damaged by wind and its flowering spoiled. It is not such a charming flower when its vulnerable yellow flowers are seen against a threatening steel-grey sky. The tree is usually planted in the shelter of a wall, but it is often too big for the allotted wall space and, when it grows higher than the wall, it can be damaged by gales.
All of these species of acacia are inclined to be top-heavy and can be rocked by strong winds that catch the heavy foliage. Wind rocking can break roots and the tree goes into decline, one of the main reasons for the loss of these showy plants. Planting into well-drained soil is the best prevention.