Tony Dickerson answers your gardening questions
Q Why does my clivia fail to bloom?
Mrs D Wilson, Leominster, Herefordshire
A Clivias are houseplants grown partly for their bold, strap-shaped, dark green leaves but mainly for the large, trumpet-shaped flowers. They’re typically orange in colour but in some forms are red, yellow or cream. Plants do best in bright, filtered or indirect light. Avoid direct sun in summer, which can scorch leaves, and never place plants near radiators.
The main reason for non-flowering is where plants are kept too warm over winter. A period of winter cooling of three to four months is necessary to initiate the flower bud and this is most easily achieved by moving plants to a cool room at 10C (50F) from November to February, before bringing them back into a temperature of 16C (60F).
Other reasons for non-flowering include planting too deep, over-potting in large containers or under-watering when in active growth, which may lead to flower buds failing to develop.
This is a good time of year to repot if you haven’t done it in recent years. If the bulbs are very congested wash the old potting compost off in water, taking care not to damage the fleshy roots, then pull the bulbs apart. Use a well-drained John Innes No 3 with added multi-purpose and sharp sand or grit.
A pot about 20cm (8in) in diameter should be fine for a large bulb, or two or three smaller ones. It needs to just accommodate the roots and the neck of the bulb should be above soil level. After this, water sparingly, applying a tomato fertiliser every 10 days or so until the end of summer.
After flowering, cut the stem at the base, unless seed is required. Reduce watering over the winter, but never allow plants to dry out completely.
Clivias are expensive to buy, so if your plant sets seed it’s worth growing it on. Harvest when berries turn red and sow immediately without allowing the seed to dry out. Use small pots of John Innes No 1, covering seed with grit. Germination takes six to eight weeks at 21C (70F). Grow seedlings on at 16C (60F), feeding with tomato fertiliser and potting on as necessary. Flowering is likely to take three to four years.