GARDEN GURU

Q A decade ago, my son removed a seedling from the trunk of a tree fern. It’s now a vigorous tree with two types of leaves. Do you recognise it? Caroline Fairweather A The tree in your photo is a type of acacia – it’s difficult to be more precise, as there are at least 1,000 species. Tree ferns are shipped from Australia and often carry seeds of other plants that were growing nearby.

Q We have a large cardoon with several stems. Can we split it to make more plants? Stewart Newton

A Related to globe artichoke, cardoon has huge, jagged silver leaves and thistle-like flowers on 8ft-tall stems. One way to propagate this beauty is to lift clumps, divide into several pieces and replant in the spring.

Q We have a smoke bush Q that’s been in the garden for more than 40 years. This year the display of flowers is poor and the plant has lost many of its lower branches. What can we do to save it?

Mary Newton

A Smoke bush, or cotinus, is a deciduous shrub grown for its foliage and clouds of wispy summer flowers. These shrubs can grow very tall but tend to put on the best display when kept at a more manageable size. It might sound scary, but I would suggest hard-pruning yours in early spring, cutting back all stems to within 2ft of the ground before leaves appear. It may sulk for a season, but the plant will eventually become bushier and more floriferous.