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On warm days, open vents and doors of greenhouses to reduce humidity and help prevent disease.

Many conservatory shrubs can be pruned in early spring. Shorten the stems of Cestrum, Brugmansia, Argyranthemum, Abutilon and Acalypha, making the cuts just above a shoot. Although this task is not essential, it ensures that plants remain compact.

At the beginning of the month prune back stems on pot-grown overwintered fuchsias, and place them in a well-lit, warm spot to re-shoot. Re-pot them in fresh compost if necessary, and start feeding six to eight weeks later (or immediately if in old compost).

Deadhead Hippeastrum (amaryllis), leaving the flower stalk(s) 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.

Schlumbergera truncata and S. x buckleyi (Christmas cacti): twist off some of the stem segments, 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.

Stand houseplants on trays of damp gravel to counteract the drop in humidity while central heating is still on.

Water houseplants sparingly until they come into active growth with the advancing spring (this depends on your local weather patterns).

Clean shiny-leaved plants with a damp cloth and spiky plants with a soft brush.

Check houseplants to see if they are potbound. Pot up if necessary.

If the leaves on pot Cyclamen start to turn yellow, this may be a sign of overwatering. 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 did not go down at all, 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.

Maintain a minimum of 5°C (43°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.

Soft tip cuttings can be taken from fuchsias this month.

Don't leave houseplants overnight on windowsills behind the curtains, if there is a risk of frost, especially if your windows are not double-glazed.

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).

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.

Citrus trees in pots should be top-dressed with fresh compost, and/or re-potted if necessary.

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.

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. 

Begonia, Gloxinia and Achimenes tubers can still 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.

Start cannas into growth by potting up the dormant rhizomes at 16°C (61°F) in a light position. Water them sparingly at first, increasing irrigation as growth develops, and potting on when 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.

Check that light levels are sufficient for houseplants. They will need light to carry on until the spring. Check that greenhouse panes are clean, and take care not to leave houseplants in a back room that receives little natural light, or has the curtains drawn. They are best moved to sunny positions until late March, or whenever light levels increase to such a level that houseplants need re-positioning out of direct sunlight.

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.

Try growing on plug plants in your glasshouse. They are a relatively cheap source of large numbers of plants, and avoid the need for propagation facilities and time-consuming pricking out.

Cacti and Clivia houseplants should still be kept dormant until spring weather is definitely under way (early or late March, depending on your local weather). Very little water and no feeding is advised during dormancy. Clivia additionally benefits from lower light levels (e.g. a back room where the lights are never turned on and there is not too much natural light) - to improve flowering the following season. Once spring has definitely arrived, watering, feeding and added light will combine to bring the plants back into active growth.

Regularly pick over plants and sweep up fallen debris, to prevent disease spreading.

In colder areas, check that your glasshouse insulation remains secure.

In warmer areas, you may be able to put away the glasshouse heater. But remember that temperatures can still drop at night. Last year we had frosts until late May in southern England. Seedlings in particular can object to wide temperature fluctuations. A heated propagator could be a more cost effective answer than continuing to heat the whole glasshouse, if it is full of otherwise hardier plants in a very mild area (such as south west England).

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.

You could use spare space in the glasshouse to warm up growing-bags for use in the vegetable garden.

Keep alpine houses well ventilated.

Pest & disease watch

Check regularly for signs of pests, particularly as temperatures increases. Use organic or chemical controls as necessary.

Pick up dead or fallen leaves and flowers to deter Botrytis (grey mould).

Ventilating the glasshouse or conservatory on mild sunny days will help to reduce fungal infections.

As the weather gets warmer, insect and pest populations rise. It is wise to control early infestations before they become unmanageable - removal by hand is often enough in the early stages.

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.

Unhealthy looking Cyclamen could also be suffering from vine weevil attack, so gently knock the plant out of the pot to check the roots for signs of larvae, treating accordingly.

Look out for damping off disease on seedlings, and treat appropriately.

 

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This site was last updated 24-01-2008