Greenhouse Monthly Planner

The aim of this website section is a guide on what to do in the greenhouse or polythene tunnel on a monthly basis, if you own a greenhouse or polythene tunnel or even a simple coldframe you have the opportunity to extend the growing season, and maybe grow plants that are not suitable for your climate outside, you are able to start your seed sowing earlier, The heart of a gardening year is a work plan, twelve months of gardening and why not take advantage when you have a greenhouse

January

Water houseplants sparingly.

Indoor forced bulbs that were in the house for Christmas displays, but which have now finished flowering, can be left outside in a sheltered spot in the garden, to finish dying down.

Support bulb flower spikes with canes (if necessary).

Cut back leggy Hypoestes (polka dot plant), Pilea (aluminium plant), Coleus and Tradescantia to encourage new growth.

Encourage bushy growth on Christmas cacti (Schlumbergera truncata and S. x buckleyi) by twisting off outer segments from the most vigorous shoots after flowering. These can be used as cuttings if dried and kept warm for a week before potting up.

Maintain a minimum of 5°C to prevent Fuchsia, Pelargonium and other tender plants being killed by the cold. Higher temperatures will be needed for tropical plants.

Fuchsias can be started into active growth by re-potting, increasing watering, feeding (with a slow-release fertiliser such as fish blood and bone), and putting them in a sunny place.

Don't leave houseplants on windowsills behind the curtains on frosty nights, especially if your windows are not double glazed.

Remember that cacti need very little water, and no feeding, over the winter. Keep them barely moist until the spring, when they will be coming up to flowering and will therefore appreciate extra water and feed.

Clivia benefit similarly from a dormant period over winter, with less watering, feeding, and lower light levels.

Pot up Hippeastrum (amaryllis) bulbs, and bring them into active growth with regular watering and feeding. They should give you beautiful flowers for the late winter/early spring.

If your Christmas cactus (Schlumbergera truncata and S. x buckleyi) failed to set flower buds, it may be that the temperature is too high (above 18°C/65°F, or that the plant is receiving light from an artificial light source after dark. Try moving the cactus into cooler conditions or away from night lighting.

Cyclamen persicum (often given as a winter pot plant) appreciates a cool room with good light. It is best watered from below (i.e. into the saucer, not the pot), as wetting the leaves can easily result in fungal infections and rotting off.

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 over the winter, and can easily be forgotten in a back or spare room that receives little natural light, or with the curtains left drawn. They are best moved to sunny windowsill until March.

Avoid buying poinsettias that have been accidentally chilled, particularly those sold from street stalls on cold days. Once home, place poinsettias in a warm, light place, away from draughts, to ensure they last for as long as possible.

Place hyacinths in a cool, bright place in the home. If it's too warm, the leaves will elongate and the flowers will fade quickly.

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 to make sure it is still secure.

Remove snow from glasshouse and conservatory roofs, to prevent damage and to allow good light penetration.

Clear leaves and twigs from guttering on greenhouses and sheds.

Pest & disease watch

If leaves on pot Cyclamen start to turn yellow, this may be a sign of over-watering. Keep them in a cool, well-lit place. Water from below (into the saucer), and allow the plant to drink for up to half an hour before pouring away the excess water left in the saucer.

Look out for Cyclamen grey mould.

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

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 mealybugs and scale insect nymphs.

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

This is a good time to clean all your old pots and seed trays, so that they are ready for next spring’s flurry of activity. Thorough cleaning will reduce pest and disease problems, and will reduce your propagation and sowing problems. A Citrox solution will clean well, without unpleasant odour or toxicity to plants

February

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 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.

Stand houseplants on trays of damp gravel to counteract drop in humidity in centrally-heated homes.

Water houseplants sparingly until they come into active growth with the advancing spring.

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 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.

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.

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.

Soft tip cuttings can be taken from fuchsias this month.

Don't leave houseplants on windowsills behind the curtains on frosty nights, especially if your windows are not double-glazed.

On sunny days, ventilate the glasshouse or conservatory, to reduce the risk of fungal infections.

Prune conservatory climbers towards the end of the month:

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 repotted 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 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.

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, and can easily be forgotten in a back or spare room that receives little natural light, or with the curtains left drawn. They are best moved to sunny positions until March.

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.

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 never turned on and there is not too much natural light) - this will improve flowering in the following season.

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

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.

Keep alpine houses well ventilated.

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.

Pest & disease watch

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

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

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 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.

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

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.

March

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, andplace 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).

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.

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

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.

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.

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.

April

Increase the watering of indoor and conservatory plants as days lengthen. Check if plants need watering at least every few days. Seedlings will need daily attention.

Liquid feed once plants show signs of growth.

If the weather is warm and sunny, you may need to start damping down the floor of the greenhouse, splashing water over it to increase humidity levels in the whole glasshouse.

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

Keep alpine houses well ventilated.

Apply a light covering of shade paint on greenhouse panes, to prevent plants becoming scorched by bright sunshine. Alternatively, a sheet of newspaper or some shade netting from the garden centre work fine as temporary shading for seedlings and young plants.

Pot up houseplants showing signs of being root-bound or top dress large containers with fresh compost.

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

Brush up fallen compost and debris, and pick off dead leaves from plants. This will help prevent pests and disease spreading.

Maintain a minimum of 5°C 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.

Begin feeding citrus plants with a proprietary citrus feed, or using a high-nitrogen feed with added trace elements.

Pot up any Begonia, Gloxinia and Achimenes plants that you started off earlier in the spring and are now large enough to re-pot.

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.

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. Alternatively, feed only for a few weeks (to build up the bulb) and then reduce the watering, let the leaves die back, and allow the plants to dry out completely. The bulbs can be ‘rested’ like this under the greenhouse bench or in a cupboard if they are houseplants), to be brought out in late summer or autumn, for flowering the following winter.

Rest pot cyclamen that flowered over the winter, reducing watering until the foliage starts to die down. The pots can be placed under the greenhouse bench (or in cupboard if they are houseplants), to be started back into growth in late summer.

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.

Take leaf cuttings of Streptocarpus plants.

Hydrangeas and fuchsias can be propagated from softwood stem tip cuttings.

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.

Don’t forget to give glasshouse plants more space as they put on new growth. This will help to prevent disease, and to contain early pest infestations.

In warmer areas, you can probably 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 object to wide temperature fluctuations. A heated propagator could be a cost effective answer if your glasshouse is otherwise full of hardy mature plants.

In reliably mild areas you can start to harden off half-hardy bedding plants that were started off early under cover. By placing them outside for a short period only, at the warmest time of day, and then gradually increasing the length of time until they are outside permanently, you can avoid the shock that they otherwise experience when moved outside suddenly.

Clear leaves and twigs from guttering on greenhouses and sheds.

You could use spare space in the glasshouse to warm up grow-bags ready for planting.

Pest & disease watch

Brush up fallen compost and debris, and pick off dead leaves from plants. This will help prevent pests and disease spreading.

Damping off of seedlings can be a problem with sowings under glass. Clean equipment and, where necessary, use of fungicides such as Bio Cheshunt Compound can help to control this problem.

Insects start to emerge as temperatures increase. A mild spring can see pest problems developing earlier than usual.

May

Move conservatory plants, such as Cymbidium, Ficus and Citrus outdoors during warm days but bring back inside if cold nights are expected.

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

Pot up houseplants showing signs of being rootbound or top dress large containers with fresh compost.

Check plants at least every few days, to see if they need watering. Seedlings will need daily attention. Use rain, grey or recycled water wherever possible.

Continue to prick out and pot on new seedlings and cuttings.

Harden off your half-hardy bedding plants that were started off early under cover. By placing them outside for a short period only, at the warmest time of day, and then gradually increasing the length of time they are outside, you can avoid the ‘shock’ that they otherwise experience when moved outside suddenly and permanently.

Hydrangeas and fuchsias can be propagated from softwood stem tip cuttings.

Pot on any Begonia, Gloxinia and Achimenes plants that you started off earlier in smaller pots, but which are now large enough to re-pot in the next size up.

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.

Don’t forget to give glasshouse plants more space as they put on new growth. This will help to prevent disease, and to contain early pest infestations.

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.

Train the new stems of passionflowers over frames or on horizontal wires.

Apply shade paint to the outside of the glass or use blinds on sunny days to prevent temperatures from soaring.

Open doors and vent on greenhouses to increase ventilation on warm, sunny days.

Damp down the floor of the glasshouse regularly on hot days, to increase humidity levels. This benefits plant growth and also reduces the risk of pest problems such as glasshouse red spider mite.

Pest & disease watch

Regularly inspect plants, and also the structures of the greenhouse and conservatory, for glasshouse red spider mite, whitefly, thrips and other pests. Careful attention to the undersides of the leaves, and to each plant in turn, can spot early infestations that would otherwise be missed. Control with approved treatments, and hang yellow sticky traps to help monitor numbers of flying pests.

Damp down the floor of the glasshouse regularly on hot days, to reduce the risk of problem.glasshouse red spider mite.

Brush up fallen compost and debris, and pick off dead leaves from plants. This will help prevent pests and disease spreading.

Damping off of seedlings can be a problem with sowings under glass. Clean equipment and, where necessary, use of fungicides such as Bio Cheshunt Compound can help to control this problem.

June

Move conservatory plants, such as Cymbidium, Yucca, Ficus and Citrus outdoors during warm days but bring in if cold nights are expected.

Pot up houseplants showing signs of being rootbound or topdress large containers with fresh compost.

Check plants at least every few days, to see if they need watering. Seedlings will need daily attention. Use rain, grey or recycled water wherever possible.

Continue to prick out and pot on new seedlings and cuttings.

Harden off half-hardy bedding plants that were started off under cover.

Pot on any Begonia, Gloxinia and Achimenes plants that you started off earlier in smaller pots, but which are now large enough to re-pot in the next size up.

Try growing on plug plants in your glasshouse. They are a relatively cheap source of large numbers of plants, and can be ordered and grown on quickly if you didn’t get round to sowing seed in good time earlier this season.

Don’t forget to give glasshouse plants more space as they put on new growth. This will help to prevent disease, and to contain early pest infestations.

Train the new stems of passion flowers and other climbers over frames or on horizontal wires.

Apply shade paint to the outside of the glass or use blinds on sunny days to prevent temperatures from soaring.

Open doors and vent on greenhouses to increase ventilation on warm, sunny days.

Damp down the floor of the glasshouse regularly on hot days, to increase humidity levels. This benefits plant growth and also reduces the risk of pest problems such as glasshouse red spider mite.

Pest & disease watch

Vine weevil larvae can be a serious pest of containerised plants, and become active this month. Tip out the rootball of suspect plants, and inspect for the creamy, orange-headed maggots, which tend to curl up into a ‘C’ shape. There are various chemical and biological controls available.

Regularly inspect plants, and also the structures of the greenhouse and conservatory, for glasshouse red spider mite, whitefly, thrips and other pests. Careful attention to the undersides of the leaves, and to each plant in turn, can spot early infestations that would otherwise be missed. Control with approved insecticides and biological controls, and hang yellow sticky traps to help monitor numbers of flying pests.

Brush up fallen compost and debris, and pick off dead leaves from plants. This will help prevent pests and disease spreading.

Foot and root rots can affect young plants grown from seed and cuttings, especially those grown under glass. Clean equipment and, where necessary, use of fungicides such as Bio Cheshunt Compound can help to control this.

July

Many indoor plants benefit from being placed outside on the patio for the summer. Moving many plants out of the conservatory will save them from baking under glass, and lessen some pest and disease problems, such as red spider mite.

Ventilate and shade sunrooms and conservatories to prevent scorch damage to remaining plants.

Water houseplants freely when in growth, and feed as necessary (often weekly or fortnightly). Water plants in early morning or late evening to avoid the risk of leaf scorch on hot days.

Damp down greenhouses on hot days.

Cuttings can be taken and grown on in the glasshouse. Fuschias and pelargoniums are good candidates.

Carry on pricking out any seedlings sown earlier in the season, when they are large enough to handle. Other young plants, already pricked out, may be ready for transplanting to larger pots.

Pest & disease watch

Tidy up fallen leaves, flowers and compost - this will prevent potential pest and disease problems.

Many conservatory and greenhouse pests will be active during the summer months. Check plants regularly for signs of glasshouse whitefly, leafhopper, glasshouse red spider mite, mealybugs and scale insects.

Yellow card sticky traps are a valuable, low-cost tool for monitoring numbers and types of flying pests in the greenhouse. If large numbers of a particular pest are found, treatment can be instigated.

Ensuring that greenhouse plants are kept in appropriate cultural conditions will help them resist attacks by pests and diseases.

August

Ventilate conservatories to their maximum to prevent soaring temperatures. Use shading if necessary.

Water houseplants freely when they are in growth.

Feed plants when necessary, usually once every one to two weeks with a liquid feed.

Damp down greenhouses on hot days to maintain humidity levels.

Cyclamen that have been resting over the summer can be started back into growth for winter blooms. Watering and careful replacement of the top layer of compost should be sufficient to ‘wake’ them.

Hyacinths, ‘Paperwhite’ daffodils, freesias, and Lachenalia corms can be planted in bowls now to achieve flowers for Christmas. Once they have put on 2.5cm (1in) growth, they can be taken into a cool room, only to be brought into a warm room in time to flower for the festive period. Bulbs sold as ‘prepared’ can be forced by plunging the planted bowls in a cold, dark place for a few months, then bringing them straight inside to flower.

Pest & disease watch

Many conservatory and greenhouse pests will be active during the summer months. Check plants regularly for signs of glasshouse whitefly, leafhopper, red spider mite, mealybugs and scale insects.

Clean up fallen leaves and spilt compost from benches and floors to prevent pests and diseases spreading.

September

Plant up containers with Hippeastrum (amaryllis) bulbs and prepared hyacinths for a Christmas display.

Ventilate conservatories during the remaining warmer days to prevent soaring temperatures, but reduce ventilation once the cooler and gusty autumn weather sets in. Use shading paint or blinds to help keep them cool, but be ready to reduce shading towards the end of the month as light levels fall.

Damping down usually becomes unnecessary as the month progresses. It is best to do any watering or damping down earlier in the day, so that the greenhouse is dry by evening. Dampness during the cool nights could be a recipe for fluffy grey mould (Botrytis) and damping off of seedlings.

Start to reduce watering of houseplants as light levels drop.

Pest & disease watch

September is an ideal time of the year to apply biological controls for use on vine weevil. Grubs will be starting to hatch, and soil and compost temperatures are now suitable for the nematodes to be effective. Target vulnerable plants, such as fuchsias, succulents and containerised plants.

When bringing plants indoors, check carefully for any pests and diseases they may have picked up outside, in particular red spider mite, mealybug and scale insect. Inspect rootballs and compost for vine weevil larvae and treat where necessary.

October

Reduce watering of houseplants as the days shorten and growth slows.

Stand tropical houseplants on trays of wet gravel to counteract the drop in humidity when the central-heating comes on. Grouping them together can also help to create a more humid microclimate.

Pot up prepared hyacinth bulbs if not done last month. This way you will have them flowering for Christmas or New Year.

Plant up containers with Hippeastrum (amaryllis) bulbs for a New Year display.

Sweet peas can be sown early, in the glasshouse, for next spring.

Remove any shading paint applied earlier in the season, in order to maximise reducing light levels late in the season.

Greenhouses can be insulated using plastic bubble wrap. This will cut down the heating bills for the winter, but do make sure to attach the polythene in such a way as to minimise the amount of light blocked out by strips of tape etc, as the wrap itself will reduce light levels somewhat.

Check that the greenhouse heater is still working. Replace any spent wicks or broken parts on paraffin heaters, and get electric or gas heaters serviced if necessary.

Ventilate greenhouses and conservatories during the remaining warmer days, but reduce ventilation once cooler, gusty autumn weather sets in.

Damping down becomes unnecessary as the month progresses. It is best to water or damp down the floor earlier in the day, so that the greenhouse is dry by evening. Dampness during the cool nights could be a recipe for fluffy grey mould (Botrytis) and damping off of seedlings.

Pest & disease watch

Clean the glasshouse if not done last month, to prevent pests and diseases from overwintering in nooks and crannies.

Take care when watering indoor plants, not to wet the leaves (although this is not a problem with foliage houseplants where you are trying to increase humidity around the leaves). They will take longer to dry out in the cooler weather, and dampness could promote development of fungal disease. It is also best to water in the morning, so that the plants have time to dry off before the cold nights.

Check and pick over plants regularly, removing pests, yellowing or dead leaves and faded flowers before rots develop. Slugs are often found lurking underneath pots.

When bringing plants inside, check carefully for pests and diseases they may have picked up in the garden, particularly red spider mite, mealybug and scale insect.

Unhappy looking plants can always be tipped out of the pot to examine the rootball for signs of over- or underwatering, or for soil-based pests like vine weevil.

November

Pot up Hippeastrum (amaryllis) bulbs, and bring them back into active growth with regular watering and feeding. They should give you beautiful flowers for the festive season.

Reduce watering and feeding of houseplants as the days shorten.

Check any bulbs (e.g. hyacinths and ‘Paper White’ daffodils), being forced in darkness into early growth. When they have made about 2.5cm (1in) growth, bring them into a light, cool room or frost-free greenhouse to grow on. When flower buds appear, they can be brought into warmer rooms to provide a seasonal display.

Cacti and succulents need a period of relative dormancy over the winter: keep them barely moist, and do not feed. Resume normal care next spring to bring them back into active growth and flowering.

Christmas cacti can be managed in the same way as other cacti, or in reverse, for flowering at Easter or Christmas respectively.

Clivia benefit similarly from a rest period over winter.

Pelargoniums can be cut back, de-leaved, watered less, not fed, and kept relatively dormant and just moist, over the winter. Re-potting, watering and feeding in the spring will bring them back into active growth. They must be kept at around 10°C (50°F) while dormant.

Cyclamen can be sown now, with a bottom heat of 12-15°C (54-60°F). They will need about 14 months to produce flowers. See The RHS Propagating Plants by Alan Toogood, ISBN 0-7513-0365-8 for further information.

Lily-of-the-valley (Convallaria) can be dug up, potted and forced in the greenhouse at this time of year. Rhizomes that are kept in a frost-free greenhouse over winter will stay in active growth, but given a little heat, they will be ready to flower shortly after replanting in the garden next spring.

Stand tropical houseplants on trays of wet gravel to counteract the drop in humidity when the central heating comes on. Grouping them together also helps to create a humid microclimate around your houseplants.

Heat &/or insulation will be needed to keep the greenhouse frost free. A fan or paraffin heater should do the trick in small glasshouses. Maintaining higher temperatures will need more careful planning, and a better greenhouse heating system. Greenhouse insulation can help keep out the frost from the whole, or from a section, of the greenhouse.

Complete cleaning out spent crops from the greenhouse, if not yet done. Clean and disinfect the greenhouse structures with Jeyes Fluid or Citrox.

Make sure you have removed all shading paint from the greenhouse panes, in order to maximise light levels in the darker months of the year. If applying glasshouse insulation, to attach it only to the sides and north facing roofs to let in as much light as possible.

If you enjoy working in your glasshouse over the winter, then consider installing greenhouse lighting to make this possible even on dull days and during the evening or early morning.

Pest & disease watch

Cyclamen are prone to grey mould at this time of year.

Keep an eye out for pests, as they may become more active in mild spells during the autumn.

Slugs are often found lurking underneath pots and other protected areas.

Many pests can overwinter in nooks and crannies in the glasshouse structure (especially in wooden houses), and in the bark of woody houseplants and vines. Mealybugs and scale insect nymphs are commonly found and should be picked off. Grape vines often have their old bark stripped off before winter, to reduce the number of hiding places for pests like these.

Regularly pick off and sweep up yellowing or dead leaves, and faded flowers, before disease problems develop and spread.

This is a good time to clean all your old pots and seed trays, so that they are ready for next spring’s flurry of activity. Thorough cleaning will reduce pest and disease problems, and will make your propagation and sowing yields much greater.

Maintaining some air movement in the glasshouse or conservatory, even when the weather is cold, will help to reduce problems with fungal diseases such as Botrytis (fluffy grey mould). Opening vents slightly (but not enough to create damaging draughts) in the morning, and then closing them in the early afternoon to conserve heat, will provide enough ventilation to help keep fungal problems at bay.

Check that the greenhouse heater is still working, if you have not done so already. Replace any spent wicks or broken parts on paraffin heaters, and get electric or gas heaters serviced if necessary.

Take care when watering house- and greenhouse plants - you shouldn’t wet the leaves, as they take a long time to dry in the cool November weather, and dampness can encourage fungal diseases. It is best to water in the morning, giving leaves time to dry off before the night

When bringing plants into the house or greenhouse, check them carefully for any pests and diseases they may have picked up in the garden. Unhappy looking plants can always be tipped out of the pot to examine their rootballs for signs of over or under watering, or for soil pests like vine weevil larvae.

December

Reduce watering and feeding of houseplants as the days shorten. Ensure that there is adequate ventilation in the greenhouse or conservatory, perhaps opening vents for an hour or two on milder days to encourage air circulation.

Clivia benefit similarly from a dormant period over winter, with less watering, feeding, and lower light levels.

Pot up Hippeastrum (amaryllis), and bring them back into active growth with regular watering and feeding. They should give you beautiful flowers for the new year.

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.

Avoid buying poinsettias that have been accidentally chilled, particularly those sold from street stalls on cold days. Once home, place them in a warm, light place, away from drafts, to ensure they last for as long as possible.

Place hyacinths in a cool, bright place in the home. If it's too warm, the leaves will elongate and the flowers will fade quickly.

Put up insulating material such as bubble wrap on the inside of the greenhouse, if not already done.

Check that greenhouse heaters are functioning properly. Invest in a maximum-minimum thermometer to enable accurate monitoring of the temperature in your greenhouse.

Clear leaves and twigs from greenhouse and shed gutters.

Pest & disease watch

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 mealybugs and scale insect nymphs, for example.

Occasionally ventilating the greenhouse or conservatory for an hour or two on mild days will help reduce fungal infections.

Regularly deadhead winter-flowering plants in the home and greenhouse, to prevent problems with grey mould (Botrytis). Cyclamen are particularly prone to this problem.

Regularly pick and sweep up fallen debris to prevent disease appearing and spreading.