Cacti and Clivia houseplants should still be kept dormant until March. Very little water (barely moist) and no feeding is advised until then. Clivia will additionally benefit from lower light levels (e.g. a back room where the lights are rarely turned on and there is not too much natural light) - this will improve flowering for the following season.
Deadhead Hippeastrum (amaryllis) leaving the flower stalk to die down naturally. Keep feeding and watering and you may be treated to further flowers in August as well as the normal blooms next winter.
Keep Cyclamen in a cool, well-lit place and water them from below (into the saucer). Allow the plant to drink for half an hour, before pouring away the remaining water left in the saucer. If the level in the saucer does not go down, then the plant did not need a drink. You can always tip out the rootball and feel it before watering, to see if the compost is dry, or if it is still moist from previous watering. If the leaves on pot Cyclamen start to turn yellow this may be a sign of overwatering.
Citrus trees in pots should be top-dressed with fresh compost, and/or repotted if necessary.
Cool conditions and regular watering will help keep potted indoor azaleas looking good for longer. Remember to water azaleas with rainwater collected in a rain butt, not with tap water.
Indoor forced bulbs that were in the house for winter displays, but which have now finished flowering, can be left outside in a sheltered spot in the garden to finish dying down.
General houseplant care
Pruning and training
Plumbago, passion flower and jasmine can be thinned out, so that they have a neat framework of branches. The previous year’s growth can also be cut back to two or three buds from the main framework, to keep the size under control.
Bougainvillea pruning is sometimes left until early spring the year after flowering, because of the risk of frost damage when pruning in the autumn, just after flowering. Last year’s growth should be spur-pruned back to 2.5cm (1in) of the main woody framework. Do not prune unless the glasshouse or conservatory is reliably above 10°C (50°F).
Schlumbergera truncata and S. x buckleyi (Christmas cactus) - twist off some of the stem segment, with a view to keeping a balanced shape to the plant. This will encourage bushy growth. The detached segments can be used as cuttings, if dried and kept warm for a week, before potting up in gritty compost.
Cut back leggy Hypoestes (polka dot plant), Pilea (aluminium plant), Coleus (now called Solenostenum), Tradescantia, Pelargonium, Salvia, Argyranthemum and Lantana to encourage new growth and keep the plants well shaped. Prunings can always be used as softwood cuttings.
In the greenhouse
Fuchsias can be started into active growth (if not done last month) by repotting, increasing watering, feeding (with a slow-release fertiliser such as blood, fish and bone), and putting them in a sunny place. Those that were started up in January can now be sprayed with water occasionally to raise humidity, encourage growth, and help bud break.
Greenhouse bulbs that have finished flowering (e.g. freesias and Lachenalia) can now be fed weekly with high potassium feed (such as tomato fertiliser), to build up the bulbs before resting them over the summer. Reduce feeding and watering as the foliage starts to die back, and then lay the pots on their sides under the greenhouse bench until next autumn.
Begonia, Gloxinia and Achimenes tubers ca n all be planted this month. Begonias and gloxinias need to be planted hollow side upwards; Achimenes can be planted on their sides, in trays if necessary, before potting them on as necessary once growth appears.
Lily-of-the-valley ( Convallaria ) that was lifted from the garden to use as winter-flowering pot plants in the greenhouse, should now be planted back outside.
General greenhouse tasks
Maintain a minimum of 5°C (42°F) to prevent Fuchsia , Pelargonium and other tender plants being killed by the cold. Higher temperatures (at least 12°C/54°F) will be needed for tropical plants.
- Check that glasshouse heaters are functioning properly, by investing in a maximum-minimum thermometer to enable accurate monitoring of your greenhouse temperature.
- Check your glasshouse insulation is still secure for the remainder of the cold weather.
- Clear leaves and twigs from guttering on greenhouses and sheds.
- On sunny days, ventilate the glasshouse or conservatory, to reduce the risk of fungal infections.
- Keep alpine houses well ventilated.
Take fuchsia cuttings from the soft tips this month.
If you do have any seedlings and/or cuttings in the greenhouse, make sure they are getting the maximum light available, or else they will become weak and leggy. If necessary, turn them once a day so that they get light on both sides. This will stop them leaning over towards the light, and keep them upright and compact.
Don’t forget to prick out seedlings before they get too crowded, and then to pot them on as individual transplants as soon as they are large enough.
Plug plants are now available for sale. They can be grown on in your glasshouse, being a relatively cheap source of large numbers of plants, while avoiding the need for propagation facilities and labour.
Pest and disease watch
Ventilating the glasshouse or conservatory on mild sunny days will help to reduce fungal infections.
Regularly pick over plants and sweep up fallen debris, to prevent disease spreading.
Pick up dead fallen leaves to deter Botrytis (grey mould).
Cyclamen persicum (often given as a winter pot plant) is best watered from below (i.e. into the saucer, not the pot), as wetting the leaves can easily result in fungal infections such as cyclamen grey mould and rotting off.
Look out for damping off disease on any seedlings, and treat appropriately.
Unhealthy looking cyclamen may also be suffering from vine weevil attack, so gently knock the plant out of the pot to check the roots for signs of larvae and treat accordingly.
Keep an eye out for overwintering pests such as whitefly or red spider mite and treat accordingly. Nooks and crannies, and the bark of woody houseplants and vines, can harbour nymphs of mealybugs and scale insects.