HOW DO I CARE FOR ACACIA GAULOIS ASTIER

This plant can be cut back by two thirds of its height after flowering, so not now. It is also a little tender - if the temperature falls below freezing, you will need to provide protection at the roots and over the topgrowth with fleece, or similar - regular temperatures below freezing really mean the plant should be put in a cool greenhouse for the winter.

From BBC.co uk
Mimosa
Common Name: Mimosa
Genus: Acacia
Species: dealbata
Cultivar: 'Gaulois Astier'
Skill Level: Experienced
Exposure: Full sun
Hardiness: Half Hardy
Soil type: Well-drained/light, Sandy
Height: 2500cm
Spread: 700cm
Flowering period: February to April
Mimosa makes a beautiful evergreen shrub for the conservatory or greenhouse. It also makes an attractive small tree or shrub for sheltered gardens. The architectural silvery leaves are complemented by long, bobbly, fragrant yellow flower heads in late winter and early spring. The unusual feathery foliage makes it particularly useful for creating exotic effects in sub-tropical plantings and jungle borders.