Why is my mophead hydrangea not flowering?
Julia Macleur, by email
AMATT SAYS This is often down to pruning or growing conditions. Mophead hydrangeas need dappled shade or sun, in moist but not waterlogged soil, and protection from scorching sun and cold wind. Leave the old flowerheads in place over winter, then cut back to the strongest pair of buds just below, after all danger of frost has passed. At the same time, cut out two or three of the oldest stems at the base to encourage new flowering wood to grow. Don’t cut the whole plant to ground level or it won’t flower until the following year.
Avoid nitrogen-rich fertilisers, which encourage lush growth at the expense of flowers. Instead, apply a high potassium feed in spring to encourage blooms. Mulch in spring too, as this helps to retain moisture in the soil, which is needed for flowering. Use a 7cm layer of well-rotted organic matter, such as home-made compost.