Golden mimosa - a pretty vision in the garden

Not as commonly seen in recent years, the fluffy yellow sprays of mimosa appear in florists’ shops early in the new year. These are cut flowers transported from the south of France and Italy where the weather warms up a little earlier than here, and harsh weather to damage the flowers is not as likely.

Though often associated with the Mediterranean region, mimosa is actually native to Australia and its botanical name is Acacia dealbata, one of several acacia species from that country grown here.

In full flower, it is a sight to see – often more than 10m tall and almost as wide, and covered with yellow puffy flowers. It also has the value of being evergreen – its light ferny foliage is very decorative in winter, even before the show of flowers. The foliage has a light coating of white wax which gives a pale green appearance and its other common name is silver wattle – wattle being a general name for acacias in their native land.

Because of its mature size, it is only a tree for relatively large gardens and it is usually seen in old gardens and estates, and only near the coast. It is unlikely to be seen further inland than about 2-3km because it is borderline hardy. It is very easily killed by frost as a young plant, though more resilient if it gets some mild winters to start with. Once it gets going, it grows very rapidly, easily putting on 60cm and more.

Significantly hardier, though some books say otherwise, the other acacia commonly grown outdoors is the Cootamundra wattle, Acacia baileyana.

A smaller tree to about six metres, this species has blue-green feather-like leaves, not as large as the ferny leaves of mimosa. Its flowers are more egg-yolk yellow than the lemon yellow of mimosa, but earlier to flower, the first sprays appearing before Christmas most years.

In frosty inland areas, this species can be grown in a pot and taken into a greenhouse for protection, or even grown in a green house or large tunnel with pruning. There is a very pretty form that has purple-tinged young shoots called ‘Purpurea’ and is more available than the ordinary green sort.

There are other acacias too, such as Acacia pravissima and Acacia armata, which are large shrubs suitable for greenhouse growing. These need pruning after flowering and are easier to accommodate on a warm wall than the trees. They are about as hardy as the mimosa and usually need a very favoured position in an inland area or under cover.

With willowy shoots and narrow leaves, Acacia retinodes is another species sometimes seen. The magnificent Acacia melanoxylon, or blackwood acacia, is a large tree (15 metres tall) very similar in appearance when mature to the evergreen holm oak. It has dark-green leaves of similar size, although the young shoots have the ferny foliage of its relatives. It carries lovely pale yellow flowers in late winter, high up on the tree.

This species is usually only seen in large gardens open to the public and is only for sale from specialist rare tree outlets. Century-old trees were killed by frost in 2010, but if you have a large garden near the coast, it is worth trying.

Mimosa and other acacias are members of the pea family and, like many members of that family, they like free-draining, even sandy, soil. The soil should be reasonably fertile but not rich, or the plants will grow too soft and be prone to frost.

They need good shelter and full sunshine to grow well and flower at a younger age. If the shelter is not good, the lovely ferny foliage of mimosa will be badly damaged by wind and its flowers too.

If plants cannot be found, most acacia species can be grown easily from seeds sourced from the internet, and the Cootamundra wattle occasionally self-sows in gardens. CL

Start off your

potatoes now

Early potato varieties can be encouraged to give an earlier crop by chitting or sprouting them a few weeks before planting. The seed potatoes can be placed in a single layer on a shallow tray or in egg boxes, the end with the eye-sprouts upwards. Ideally a window sill indoors or a greenhouse or shed can be used – a little warmth being good along with good, bright light. By forming sprouts early, the seed potatoes will get off to a quicker start and should give an earlier date for first lifting, at least a week and possibly three weeks have been claimed for the relatively minor intervention. It is only worth doing for early varieties as earliness of the new potatoes is not an issue for the later-storing varieties.

>> This week

Fruit, vegetables and herbs

Rhubarb stools can be lifted for forcing in a dark, warm place, or in a black bag. Sow the seeds of early varieties of cabbage, cauliflower, carrots, lettuce and onions now. These will have to be started off in warm conditions indoors or in a propagator and grown on in a greenhouse or tunnel. Prune apple and pear trees.

Trees, shrubs and roses

Roses can be pruned at any time in good conditions. Make sure that trees given a stake at planting are still solidly supported. Conditions for planting trees and shrubs, hedges and shelter belts have been generally good – but delay if the weather is wet and the ground is sticky. Control grass and weeds before planting.

Flowers

If the ground is not too wet, border flowers can be lifted and divided, if necessary. Many of these are beginning to show signs of early growth. Bedding flowers can be started off from seeds sown in a heated propagator now, but it is still too early for most of the easy kinds, such as dahlias and marigolds.

Lawns

If the ground is firm enough for mowing, this should be carried out at the first opportunity. If the soil is wet and squelchy, do not walk on it or mow it as considerable damage can be done by compaction. The lawnmower should be serviced and the blades sharpened before the new mowing season.

Greenhouse and house plants

Many Christmas houseplants, such as poinsettia, azalea and cyclamen, can be made to last longer with good care. They will need watering but only just enough to keep them moist – certainly do not leave them standing in water. Give no feeding until April. Give them good sunlight but do not leave them behind curtains.