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Gardening information, hints and tips on how to get the best from your greenhouse and cold frame throughout the gardening year.

Greenhouses and Cold Frames Hints and Tips

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Jan

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Nov

Dec

May

If not done earlier in the year, pot on tuberous begonias and gloxinias into 5in. pots. Sow sweet corn, cucumbers and melons. Apply shading to your greenhouse to protect flowering plants such as pelargoniums and hydrangeas. Water staging and floor to increase humidity. Use ventilation but take care on windy days not to open the windows on the windward side. Water and feed vigorous plants. Pinch out the growing point of 5in. high fuchsias, to encourage a bushy growth. If you want standards, take out the lower side shoots until the stem is the height you require; pinching out the growing point will then allow the top shoots to develop. Tomatoes are beginning to make growth. Tie stems to canes and remove side shoots. Feed the plants weekly, at the very least, from the time the fruits start to swell. Melons should now be planted out into cold frames, in a mixture of good manure and compost. Pinch out the growing point once there are 5 or 6 leaves. Avoid over-wetting the main stem which can lead to rot.

Buy equipment from The Potting Shed at Thompson and Morgan.

June

Check pots daily and water as required. Keep the greenhouse moist and humid to keep red spider mites at bay. Cyclamen sown last August can now be potted on into 5in. pots and then stood in a cold frame, together with primulas and solanums. Cut back pelargoniums that have finished flowering and plunge them in their pots, up to their rims, in the border. Azaleas and hydrangeas that have finished flowering can also be treated in the same way. Remove the dead flowers from greenhouse plants to prolong the flowering period. Watch for aphids and remove from plants. Melons which you planted into cold frames last month should have all but four of the side shoots removed. When the plants have reached the edge of the cold frame, pinch the end of the shoots out. When female flowers are open (they have small fruits developing), transfer pollen to them from the male flowers, using a small brush or cotton bud. When cucumbers have seven leaves, pinch out the growing tips. Water with a rose fitted to the can. Once fruits start to appear on cucumbers and tomatoes, feed with a liquid fertiliser. If you don't already have one, fit an opening mechanism to the greenhouse window; this will save you remembering to open and close it each day.

July

It is very important to carry on paying close attention to watering and damping down during hot weather – indeed watering and damping down may need to be done twice a day in really hot weather. Tomatoes will be in full fruit now and some fruit will be ready for picking almost every day – apply liquid fertilizer every week at this stage. Likewise cucumbers will also be in full production – pick the fruits when they are 12 inches long and remove male flowers if you are not growing an all female variety. The continuous requirement for watering will expose some roots on the surface of beds or pots – a top dressing of well rotted manure will be ideal at this stage as the nutrients it provides will be quickly distributed down to the root system as watering continues. At this time of year there is a real danger of fungal diseases in the greenhouse and hygiene is particularly important – get rid of all plant debris and other rubbish immediately – empty old compost from pots and clean them thoroughly before storing them.

August

Maintenance can be started towards the end of the month – repair broken panes of glass and stop any roof leaks which can be a serious problem over the coming cold season. Wooden greenhouses can be repainted with a good wood preservative before autumn rain wets the wood thoroughly. It would also be wise to check out the heating system, whatever variety you have, so that it is ready when required later in the year.

Buy equipment from The Potting Shed at Thompson and Morgan.

September

If you are growing seeds and cuttings in your greenhouse you may need to add some artificial heat towards the end of the month. Keep an eye on the forecast and if frost is threatened, turn on your heater. Annuals can be sown and grown on in pots in the cool greenhouse. Sow in a good seed compost such as John Innes and prick out once they can be handled. Vigorous plants will need a pot of their own but nemesias can be planted 3-4 to a pot. Pot on again in February. Take cuttings of pelargoniums, fuchsias, abutilons and heliotropes, standing the pots on staging. If you applied shading to your greenhouse earlier in the year, this will now need to be removed. Move plants such as primulas, cyclamen, begonias and gloxinias into the greenhouse before the weather turns cold. Houseplants such as winter flowering cactus should now be moved indoors.

October

If your tomatoes have suffered from any fungal diseases it is a good idea to fumigate the greenhouse if all other plants can be removed first of course! Fumigating candles are the best way to achieve this - close the greenhouse down and light the candle before retiring for the night and leave it closed until next morning when the door can be opened and the air allowed to circulate for a couple of hours before entering. If you are intending to heat the greenhouse over winter now is the time to line the greenhouse with insulating material - large sheets of 'bubble wrap' insulation and clips are available for this purpose.

November

Wash your greenhouse glass inside and out using warm water with detergent. Keep the greenhouse ventilated but close early in the afternoon to retain any warmth. Finish potting on annuals sown in September and cuttings of pelargoniums, fuchsias and campanulas. Any other cuttings or seeds showing good signs of growth should be potted on into 3 inch pots. Fuchsias and begonias that have finished flowering can be stored in a cool greenhouse or frost-free shed. Place under staging but do not not allow them to completely dry out. Be on the lookout for whitefly and treat with a proprietary insecticide. Water annuals sparingly and keep the atmosphere in the greenhouse as dry as possible. Avoid high temperatures as this will make your seedlings leggy.

Buy equipment from The Potting Shed at Thompson and Morgan.

December

Keep the greenhouse clean and tidy and watch for pests, especially slugs. As you empty pots scrub them ready for use in Spring. If plants that you intend to take into the house for Christmas are slow to make progress, move them into a warm room in the house. If other plants are too far ahead, move to a cooler position. Water flowering plants but otherwise only water to stop plants drying out too much.

January

Check flowering plants and remove any dead or discoloured leaves and faded flowers. Water from the bottom to avoid crowns rotting. Take care not to overwater young plants or annuals. Check cuttings to see if they are in need of water and remove any that show signs of mildew or disease. If you have a propagator, sowing of begonia and gloxinia seed can take place now. Polyanthas for indoor flowering can be brought into the house this month.

February

The gardening year is really starting to get going this month in the greenhouse and cold frame. Plants which have overwintered in the greenhouse e.g. fuschias will be just coming out of their dormant stage and will need some attention. Move them to the greenhouse staging, spray with water on sunny days and add a littlee heat to the greenhouse on particularly cold nights to protect the new growth. Tomato seeds should be planted this month if you are going to grow tomatoes in a cold greenhouse from early April. Sow the seeds two to a 3 or 4 inch pot and keep at a temperature of 16C making sure the seedlings get as much light as possible as soon as they have germinated to prevent them becoming leggy. Greenhouse climbers such as passiflora will need to be pruned back to two buds from the start of last year's growth.

Buy equipment from The Potting Shed at Thompson and Morgan.

March

Over-wintered annuals should be potted on. Tidy up plants, removing old wood, overcrowded shoots and dead leaves. Sow tomatoes ready for the greenhouse in May. If planting directly into the greenhouse border, prepare it for next month. Cannas should begin to grow if placed in moist compost. Pelargoniums now require some liquid fertiliser every couple of weeks. Begonias and gloxinias should be potted on as should all seeds once large enough. Pots should be washed out and the greenhouse tidied up.

April

Young seedlings and potted up plants will need to be shaded from the sun and the greenhouse kept well ventilated. Newly potted plants will need more water and established plants should be fed. Hydrangeas will need lots of water and feeding every ten days; cuttings can also be taken now. Plant tomatoes, providing support with canes and string. As the tomatoes grow, remove the side shoots from leaf axils. Tomatoes to be planted outdoors should be sown now, straight into 3 in. pots. Begonias and gloxinias not potted on last month, should be done now. Half-hardy plants should be moved into a cold frame. Melons, cucumbers and sweet corn should all be sown. Plants in cold frames should be given ventilation and watered regularly. Put some slug pellets in the cold frames or a slug pub.