Stefan Buczacki solves your plot problems
Judi Whi aker, Saltfleetby, Lincolnshire
Stefan says: Your mimosa is in a pot and you bought it last year when it was about 90cm (3ft) tall and in flower, wrapped it in bubble wrap and fleece last winter and put it under an overhanging roof in the garden, where it flowered beautifully this season. You then planted it in the garden where it has thrived and is about 1.5m (5ft) tall and full of flower buds.
Your garden is a mile inland from the east coast of north Lincolnshire and exposed to the north wind in winter. You need to know if it will need protection over winter because friends have said they’ve seen mimosas in snow and frost outside in France.
The mimosa your friends have seen may not necessarily be the same species or variety as yours, which I expect is Acacia dealbata, also called the blue wattle. It originates in Tasmania, which has a climate between ours and that of the Mediterranean.
Most Tasmanian shrubs, including Acacia dealbata, are given the British hardiness rating H3, which means they’ll tolerate temperatures down to -5C (23F) and are reliable in mild areas of Britain and in coastal gardens.
So where does that leave you, on the Lincolnshire coast? My feeling is that your tree will be fine provided it is in a sheltered part of the garden. If it was mine, I would leave it in its sheltered spot but be prepared to cover it with fleece if hard frosts or very cold winds are forecast.
Your tree is similar in some respects to my tree fern Dicksonia antarctica, also 1.5m (5ft) tall, also from Tasmania, also with hardiness level H3 and likes a sheltered spot. I expect my garden is colder than yours, however, so I do cover the crown with fleece every winter.