Once you have chosen the right greenhouse for your garden space and needs, whether it is a large free-standing model or a smaller lean-to variety you will need to carefully plan your gardening year to maximize the greenhouses’ use.
Below Garden World has compiled a month-by-month calendar of Greenhouse Monthly Jobs Checklist and tasks specifically for the greenhouse gardener based on the most popular uses for users of Greenhouse Gardeners.
so there are many Greenhouse Monthly Jobs Checklist that you must do all the year because of that you will learn in this exhaustive article all jobs and tasks in your greenhouse
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January – Greenhouse Job Checklist
Checking insulation and heating
Insulation benefits both greenhouses and frames and can be done simply with plastic bubble wrap. If not already done, make time to do it now. Check the heaters.
Water the plants only when the soil in the pots shows signs of drying out. Avoid overwatering annuals in pots and any other young plants in the greenhouse or the roots may be damaged. Take care not to splash the flowers or leave water lodging in the crowns of the plants. Try to water as early in the day as possible, especially in a cold or cool greenhouse, so that surfaces dry before nightfall.
Controlling Pests and Diseases
Remove any leaves showing signs of grey mold (botrytis), and discard any cuttings which have diseased stems. Check for pests such as vine weevil and take action if necessary. Where possible use dusts rather than sprays in winter to avoid increasing the humidity in the greenhouse.
If you have a heated propagator available that can maintain a temperature of 16-18°C (61-65°F) during germination, you can start sowing seeds towards the end of the month. Without the extra boost of a heated propagator, delay sowing for another month. Sow greenhouse plants, such as begonias, gloxinias, and streptocarpus, and also plants for the garden, including pelargoniums, half-hardy annuals, lilies, perennials, and sweet peas.
Lilies for forcing
If you want to force lilies to produce early flowers pot up the bulbs now.
Complete the pruning of vines in the greenhouse while they are completely dormant. Peel or rub loose bark from the stems of mature vines as this can harbor pests over the winter, but do not pull off so much bark that green shows underneath.
February – Greenhouse Job Checklist
Move dormant fuchsias, heliotropes, hydrangeas, and other pot plants on to the greenhouse staging. The ideal is a warm spot where a temperature of 10°C (50°F) can be maintained. Spray the plants with water on sunny days, and give them increasing amounts of water as growth becomes active. Remove dead and discolored foliage.
Start dahlia tubers into growth and pot-up lilies.
Check young plants and rooted cuttings regularly and pot them on into larger pots as soon as their roots fill the pot they are in.
Sow seeds of greenhouse plants such as coleus, gloxinias, tuberous and fibrous begonias, abutilon, and streptocarpus in seed trays in a heated propagator. When the seedlings are large enough to handle, prick them out into pots or trays filled with soilless potting compost and grow them on in warmth.
Also sow early vegetables, shrubs, perpetual carnations, annual climbers, parsley, and further half-hardy annuals.
To raise tomatoes in a cool greenhouse, sow the seeds this month at a temperature of 1 5-20°C (60-70°F).
It is essential that vines are properly chilled in winter, so keep the greenhouse well ventilated until growth starts. Once growing, a vine needs as much light and heat as possible, so reduce the ventilation and apply a coat of white paint on the wall of a lean-to greenhouse to increase the intensity of the light.
March – Greenhouse Job Checklist
As the weather in March becomes warmer, more use can be made of the greenhouse; seeds can be sown, bulbs planted and cuttings taken. Unless the spring is cold, you can now remove the winter insulation from the glass.
Controlling pests and diseases
Higher temperatures bring an increase in insect activity, so watch out for aphids, red spider mites, and whitefly.
Watering and feeding
Increase watering; do not let pots or seed trays dry out. Apply liquid feed to plants in pots on a regular basis as they start into growth.
The seeds of many plants can be sown this month. Sow everything listed in February. Also, sow dahlias, lilies, annual carnations, herbs, hardy annuals and any flowering plants that you plan to grow in pots. Prick out seedlings as soon as they are large enough to handle.
Annuals such as schizanthus and nemesias that have been overwintered in 8 cm (3 in) pots grow rapidly at this time of year. Pot them on into 15 cm (6 in) pots containing John Innes No.2 potting compost. Insert supporting stakes for the taller plants and tie them in as it becomes necessary. Move these plants into the house or conservatory when they start flowering.
At the end of the month, pot on gloxinias and begonias into 9 cm (3 1/2 in) pots containing John Innes potting compost No.2 with peat added at the rate of one part peat to nine parts compost.
Pot on fuschias and chrysanthemums as required.
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Take cuttings of dahlias, fuschias, pelargoniums, chrysanthemums, some shrubs, and indoor plants, such as abutilons, inserting them in a free-draining compost, preferably in a heated propagator.
Peppers and aubergines
Sow peppers two seeds to a pot at a temperature of 18-20°C (65-70°F) and remove the weaker of the two seedlings when they germinate. Sow aubergines at the same temperature, 5 mm (1/4 in) deep in pots.
Indoor tomato plants sown in February will now need extra space to prevent them from becoming drawn and spindly. Where practicable, stand the pots on the greenhouse border where they will be planted. Otherwise, space them out on the staging.
If you wish to plant tomatoes in an unheated greenhouse in May, or outdoors, and have a heated propagator or a warm windowsill, sow the seeds this month at a temperature of 15-20°C (60-70°F), covering them with a thin layer of sifted compost. Pot the seedlings individually into 8 cm (3 in) pots of John Innes No. 2 potting compost as soon as the seed leaves are fully developed.
If you have a cool greenhouse, prepare the border for planting tomatoes next month. Dig in plenty of well-rotted manure or compost and apply a balanced fertilizer. Alternatively, you can buy growing bags or use the ring culture method. To prepare the border for ring culture dig out a trench at least 20 cm (8 in) deep and line it with plastic sheeting. Fill the trench with a layer of pea gravel 15 cm (6 in) deep. Tomato plants are then grown in purpose-designed bottomless pots which can be sunk into the gravel. The plants are watered via the gravel but fed via the pot.
Once growth begins to ensure the vines get as much light and heat as possible.
April – Greenhouse Job Checklist
Shading and ventilating
The changeable weather in April can cause violent temperature fluctuations in the greenhouse. Remove winter insulation if you have not done this already. Shade young seedlings and newly ported plants from the sun with horticultural fleece or sheets of newspaper. Keep the greenhouse well ventilated, but only open those lights facing away from the wind if there is any risk from hailstones.
Watering and feeding plants
Give increasing amounts of water to all plants in pots or containers, which should now be established and growing rapidly. Continue to feed established plants such as zonal and regal pelargoniums, annuals in pots, fuschias, and other summer-flowering plants. Apply liquid fertilizer at ten-day intervals.
Hardening off half-hardy plants
Move any half-hardy plants into a cold frame for hardening off. This will also provide space for sowing melons and cucumbers at the end of the month or in early May. Plants in frames require regular watering and the lights propped open on sunny days to give them extra ventilation. Move tall plants to the back of the frame so that they do not touch the glass. Protect plants from slugs and snails.
Controlling pests and diseases
Introduce Phytoseiulus persimilis as a biological control if red spider mite is a problem – chemical controls are often less effective.
Make further sowings of dahlias, dianthus, annuals, lilies, shrubs, and vegetables. Sow winter cherry at about 15°C (60°F). Prick out the seedlings when they are large enough to handle.
Pot up rooted cuttings, and pot on cuttings and young plants which have made good growth and produced a mass of roots.
Cucumbers and melons
Cucumbers are a worthwhile greenhouse crop, and a single plant will be sufficient for most households. ‘Butcher’s Disease Resisting’ is an excellent variety. Melons of the cantaloupe type are usually grown in a cold frame or under cloches.
Sow melons and cucumbers in a temperature of 15-18°C (60-65°F). In each case sow the seeds individually about 3 (1 1/2 in) deep in 8 cm (3 in) pots of John Innes No. 1 potting compost.
Climbing cucumbers should be grown up canes, and the lateral shoots which carry most of the fruit should be trained along horizontal wires 30 cm (12 in) apart. Pinch out the growing tip and side shoots two leaves beyond a female flower.
Where a single cucumber plant is being grown, plant it on a mound. Add John Innes base fertilizer or a slow-release fertilizer at the rate recommended by the manufacturer. Female types will not require lateral training as they only fruit on the main stem.
Peppers and aubergines
Prick out into individual pots when the seed leaves are fully expanded.
In a cool greenhouse plant tomatoes in the bed prepared last month, allowing 35 cm (14 in) between plants, alternatively use grow bags. Water the tomato plant before planting.
If you are growing plants by the ring culture system, use john Innes No. 3 potting compost and bottomless containers which are 20 cm (8 in) deep and 20-25 (8-10 in) in diameter. Keep the gravel base moist after planting watering the plants in the pots just sufficiently to keep them growing. Once the roots have penetrated into the gravel, no further watering via the containers will be needed, except when the plants are fed.
Train tomato plants up tall canes or up strings. You can hang these from wires on glazing bars down to hooks of thick wire pushed into the soil alongside the plants. If you are growing tomatoes in a growing bag, take care not to push the canes through the bottom.
From the time the first tomato flowers open, spray the plants lightly at about midday during sunny weather. During dull weather, dust the flowers with a feather duster or a paintbrush. Remove all side shoots of cordon tomatoes from the axils of the leaves when they are 2.5 cm (1 in) long. Leave the side shoots on bush varieties.
Ensure vines get as much light and heat as possible once growth begins but try to maintain adequate ventilation to assist pollination.
Mai – Greenhouse Job Checklist
Shading, humidity, and ventilation
On warm, sunny days provide shade for plants, seedlings, and cuttings. Increase the humidity by damping down the staging and floor. Provide adequate ventilation, but do not open side or top ventilators on the windward side of the greenhouse on windy days.
Watering and feeding
Give the plants plenty of water, and feed vigorous plants weekly with the liquid plant food.
Controlling pests and diseases
As weather conditions improve, introduce the predator Encarsia formosa to control whitefly. You may need to make two introductions to build up its numbers sufficiently to keep the whitefly population under control.
Towards the end of the month sow cineraria seeds. This will produce plants that will flower indoors from December onwards. Sow the seeds thinly in pans of John Innes seed compost, cover lightly with compost, and germinate at a temperature of 10-13°C (50-55°F). Prick out the seedlings into a seed tray as soon as they are large enough to handle and keep them watered and shaded.
In mild areas plant out any vegetables raised in the greenhouse once they have been hardened off. Half-hardy bedding plants can also be planted out; many will be suitable for hanging baskets and containers. Move outside roses that have been forced in containers when they have finished flowering.
Taking softwood cuttings
Take softwood cuttings of suitable herbs, shrubs, and perennials; take semi-ripe cuttings of clematis.
Sow seeds soon as possible if this has not been done. Stop laterals growing from the main stems of cucumbers at two leaves beyond the first or second fruit unless they are much preferred all-female flowered type which do not make laterals and which fruit on the main stem. Cucumbers with male and female flowers will also need subsequent sub-laterals pinched out as soon as they have made two leaves beyond their first fruit. Remove all male flowers and tendrils. Pinch out the male flowers on those cucumbers that produce male and female flowers. Females have an embryo fruit behind the bloom. Pollination adversely affects the flavor.
Cucumbers with male and female flowers should also have the growing tips of sub-laterals pinched out two leaves beyond their first fruit.
Sow seed as soon as possible if this has not already been done. Plant out any melons raised from seed sown in April into cold frames, one plant to each frame light. Set out each plant on a mound of soil mixed with well-rotted compost. Pinch out the growing point when the plant has developed four or five leaves. Avoid splashing or damaging the main stem at soil level, or damping-off may occur.
Peppers and aubergines
Transplant young plants into their final positions when they are 10 cm (4 in) tall; a greenhouse border, growing bags, or 20 cm (8 in) pots are all suitable sites. Pinch out the growing tips to encourage a bushy habit. Stake tall varieties. water in and damp down the greenhouse floor to keep the humidity high.
Twist the stems of cordon tomato plants round the supporting strings, or tie them to canes, and remove side shoots regularly. Feed the plants every week or ten days from the time the fruits on the first trusses begin to swell, using a high-potash fertilizer. In a cold greenhouse, plant tomatoes in the border, in growing bags, or in bottomless containers on a gravel base using the ring culture method.
Continue to guard against powdery mildew throughout the growing season. Thin and train.
June – Greenhouse Job Checklist
Watering, shade, and ventilation
This month, pay particular attention to watering. Plants in clay or terracotta pots may need two or more applications daily during hot weather. Maintain a humid atmosphere by frequently damping down, otherwise, red spider mite may prove troublesome. Place pots on a gravel base kept as moist as possible. Apply extra shading in hot weather and, if the weather is very warm towards the end of the month, leave the top ventilators on the leeward side of the greenhouse open a little way at night.
Transfer as many plants as possible either too cold frames or to a sheltered position outdoors.
Towards the middle of the month, artificial heat will not be required in a cool greenhouse. Clean the heater and store away until autumn. However, an electric fan heater with the heat turned off can be used in the summer to circulate air and help to keep the greenhouse cool.
Controlling pests and diseases
Pests will be particularly troublesome now, with the increased warmth and plenty of soft, lush growth. Be vigilant and consider biological controls for pests such as whitefly and aphids.
In cold areas, plant out hardened-off plants after all risk of frost has passed.
Sow seeds of plants to provide indoor color next winter and spring. Suitable plants for sowing now are cinerarias, calceolarias, primulas, primroses, and streptocarpus.
Take softwood or semi-ripe cuttings of chrysanthemums, carnations, fuchsias, herbs and many perennials and shrubs, to root in the warmth of the greenhouse. A number of house and conservatory plants, including African violets and Bergonia res, can be propagated by leaf cuttings taken during the summer.
Potting up and potting on
Pot up any seedlings and cuttings taken last month that have now rooted. Check on any larger plants which may need moving into bigger pots. Streptocarpus sown at the beginning of the year should now be ready for potting on into 13-15 cm (5-6 in) pots. Handle the plants very carefully when you do this as the leaves are brittle and can be damaged surprisingly easily.
Spray regularly to maintain a humid atmosphere for cucumber plants. Pick the fruits when they are about 30 cm (12 in) long.
Pinch out all but four side shoots of melons planted last month in cold frames, stopping those shots when they have reached the corners of the frame.
Wait until there is a female flower open on each shoot, then transfer pollen to them from the male flowers. Female flowers are distinguishable by the embryo fruit behind the flower head.
Peppers and aubergines
Water regularly and give a liquid feed every fortnight. Watch out for red spider mite and whitefly. Aubergines may also succumb to powdery and downy mildew.
Water and feed regularly. Examine the mina stems of tomato plants and if they are starting to become thin, change to a liquid fertilizer which contains extra nitrogen. this will promote stronger growth.
Tie in shoots as soon as they become long enough. Water regularly and generously and feed every two to three weeks with a liquid tomato feed. Tap the branches or wipe a feather over the flower trusses in the middle of the day to assist pollination.
There can be a conflict of interest between a vine and other plants. The moist atmosphere required by many greenhouse plants can encourage fungi and mildew on a vine, while the ideal temperature for a vine, at between 26-30°C (80-86°F), can be too high for other plants. So unless you have a greenhouse devoted to the vine, you have to maintain a balance between sufficient ventilation and heat to suit the vine without overstepping the tolerances of the other plants.
July – Greenhouse Job Checklist
Damp down the borders, paths, and staging at least once a day during warm weather, but do not spray overhead as water droplets may mark the flowers of plants such as carnations and pelargoniums.
Unless the plants are standing on a capillary bench that provides water automatically, most will require watering daily and possibly two or three times a day during hot weather. To determine whether a plant needs water, press the compost lightly with your fingers. Most compost is soft and resilient, but dry compost feels hard and gritty. With a little experience, the water content of a pot can be gauged by lifting it to determine its weight. It is important not to withhold water until plants are actually flagging, but to attend to watering each day.
Shading and ventilation
Shade plants during warm, sunny weather and gives them ample ventilation, especially in the early morning when a delay in opening the side ventilators may cause excessively high temperatures in the greenhouse.
Except during unusually cold or windy weather, leave the roof ventilators slightly open throughout the night. Open them on the side away from the wind to avoid damaging droughts.
Continue to introduce biological controls if insect pest populations begin to increase. Yellow sticky traps hung inside the greenhouse will give a good indication of the current level of infestation and help you to decide whether the biological control is effective.
Sowing and potting
Continue to sow late-flowering pot plants. Prick out the seedlings when they are large enough to be handled and pot on young plants when necessary.
Take semi-ripe cuttings of hydrangeas for use as pot plants. Choose well-ripened, greenish-brown, non-flowering shoots of medium thickness; unripe shoots are light green. Insert the cuttings individually into 8 cm (3 in) pots. These later hydrangea cuttings are grown on without pinching out to produce a single head.
Similarly, take semi-ripe cuttings of carnations, chrysanthemums, herbs, pelargoniums, rock plants and shrubs. Details for these plants are given in the individual sections in June and July.
Cucumbers should be in full production by now; continue to pick the fruits when they are about 30 cm (12 in) long, and remove all the male flowers as soon as they appear. When a mass of white roots appears on the surface of the bed, apply a 5 cm (2 in) top dressing of well-rotted manure, fibrous loam or a mixture of the two.
Peppers and aubergines
Water regularly and give a feed every fortnight. Watch for red spider mite and whitefly.
Pick tomatoes daily as they ripen. Twist the stems round the supporting strings, or tie them to the canes, and remove side shoots regularly from all cordon varieties. feed tomatoes with an appropriate liquid fertilizer every week to ten days.
Thin bunches by removing any small, diseased, or otherwise imperfect fruitlets, together with any grapes that are obviously causing overcrowding. Continue to water generously, and try to maintain a balance between temperature and atmosphere.
If you want a large bunch of well-shaped and plump grapes, cut out the smallest fruits from the branches as the grapes start to swell. Use long, pointed scissors. It is usually worth doing this with outdoor grapes.
August – Greenhouse Job Checklist
Repairing, cleaning and disinfecting
Prepare the greenhouse for autumn and winter use by making any necessary repairs, such as replacing broken glass and renewing rotten wood. then set aside time to give the greenhouse a thorough clean and fumigation. This will help to prevent problems from pests and diseases over the winter.
Before cleaning the inside, remove all the plants, turn off the electricity and protect any sockets with clear plastic. Clean out all the pots, boxes and trays, and scrub containers before storage or re-use. Remove plant debris and other rubbish.
Thoroughly clean the inside of the glass with a hosepipe and brush. To remove dirt trapped between overlapping panes, first dislodge the particles with a plastic plant label or a similar flat, flexible implement, then thoroughly rinse it off with water.
Use a greenhouse disinfectant to clean the glazing bars, staging, and floor; wear protective clothing while doing this. If your greenhouse has removable staging it is usually easier to dismantle it and clean it outside the garden.
When cleaning is completed, put the plants back in the greenhouse, close all the vents, and fumigate everything with a smoke cone.
All the usual greenhouse pests will remain active and breed rapidly in the warm weather. Biological controls are very effective in a greenhouse, but be careful not to destroy them with insecticides.
Take cuttings of perennial plants, herbs, carnations, pelargoniums, shrubs, and rock plants that you want to propagate. Pinch out fuchsias to encourage shoots for cuttings.
Sow herbs in large pots for winter. Sow seeds of lilies and propagate by planting bulbils.
Greenhouse Garden maintenance
Greenhouse and frame maintenance should be carried out at least a couple of times a year if possible, and August is a good time to tackle the job as it is still warm enough to move the plants outside if you require full access.
Make sure the glass fits snugly to the frame and replace any broken panes. In an aluminum greenhouse, the glass is held in by glazing strips which can be unhooked, but in a wooden greenhouse, they may be fixed with beading, glazing bars or putty. Wet gloves when handling glass.
Cure any stubborn leaks around the edge of panes, by covering glazing bars with mastic tape.
Clean out debris from guttering and check that the brackets are sound and firmly attached. Check for leaks – a leaking gutter is a common cause of rotting frames in a wooden greenhouse. Small leaks can be repaired with mastic, but for larger leaks fit new gutters and downpipes.
Check the wood on frames and staging. Cut back any rotten wood to where the wood is sound and replace it with naturally durable wood, such as western red cedar or pressure-impregnated timber.
Rub down new bare wood with steel wool. Seal knots of shellac knotting, then paint with an exterior wood stain or primer and gloss paint. Strip off the old paint if necessary (remove nearby glass if using a blow torch), then rub down.
Clean glass thoroughly, but be prepared to reapply to shade if the summer is hot and sunny.
Replace broken or cracked panes – this will look better and reduce the risk of further damage in high winds. Cold draughts will also be reduced.
Pay particular attention to gaps between the panes, where dirt and algae can accumulate. Clean these out by pushing a thin label between the panes, then use a jet of water from a hose or compression sprayer to remove the loosened dirt.
Take the opportunity to disinfect staging and fumigate as appropriate.
Pot up seedlings sown last month and move cuttings into individual pots when rooted.
Peppers and aubergines
Harvest the first fruits. Continue to water, but reduce the amount towards the end of the month.
Remove the growing tips of tomato plants by the middle of the month to encourage the rapid development of the fruits on the top trusses. At the end of the month discontinue feeding and reduce watering. This helps to prevent fruit splitting. If the nights turn chilly, close the ventilators early in the evening.
Continue to water and feed regularly, reducing the watering as the fruit starts to ripen. Splitting fruit, a common problem, is usually caused by allowing the soil to become bone dry between drenchings. Remove any fruit and leaves affected by mildew to stop it from spreading.
September – Greenhouse Job Checklist
In this transitional period o the year, as summer changes into autumn, a little artificial heat regulated by a greenhouse thermostat may be beneficial to your plants.
Towards the end of the month remove the shading wash from the glass if you have not done this before. If the weather becomes hot and sunny you can always provide local shading for young and tender seedlings and cuttings, using paper, butter muslin or horticultural fleece.
Clean and disinfect the greenhouse now if this was not carried out last month.
Pests and diseases
By the end of the month the atmosphere in the greenhouse is likely to be damper and cooler, so be alert to signs of grey mold.
Bringing in tender plants
Before the nights turn too cold bring into the greenhouse any young or tender plants that have been outside in frames or in the garden during the summer. Discard any plants of indifferent quality and check carefully for signs of pests and diseases.
Annuals, such as cornflowers, calendulas, nemesias, and godetias, sown in early September and grown as pot plants in a cool greenhouse, will make a colorful display during spring and early summer next year. Schizanthus is another excellent plant to grow in this way. Plant the seeds in trays of seed compost, and keep at a temperature of 13-15°C (55-60°F), and prick out the seedlings onto 8 cm (3 in) pots of potting compost as soon as they are large enough to handle. Plant one seedling per pot. Keep the plants over the winter on a shelf near the glass.
If you have not already done so, it is still possible to take cuttings of a number of plants that can be overwintered undercover. These include tender perennials, herbs, shrubs, fuchsias, pelargoniums, and house plants.
Reduce ventilation and watering as the grapes ripen and stop feeding as soon as the grapes start to color. Remove leaves which are covering the grapes. This will assist ripening. Pick bunches as they ripen and remove any mildewed fruit and leaves at the same time. This helps to reduce the spread of the fungus.
Tomatoes, peppers, cucumbers
Harvest before the first frost of the greenhouse is not heated. It is not normally economical to heat a greenhouse sufficiently to continue growing tomatoes. Once quality deteriorates, strip most of the leaves from the tomatoes and peppers to encourage the ripening of any remaining fruit.
October – Greenhouse Job Checklist
Watering and feeding
As the days get shorter and the nights become colder, progressively reduce damping down and watering in the greenhouse. If it is still necessary, try to do it before midday. Stop feeding plants.
Check the greenhouse heating and make sure it is working properly and that thermostats are operating correctly. To save heat during the winter, line the greenhouse with plastic sheeting or bubble plastic. There are special clips you can buy to hold them in place. If you are using an oil or gas heater leave the ventilators on the sheltered side of the roof open 5 mm (1/4 in) the whole time to allow fumes and moisture vapor, created by the heater, to escape.
Clean the glass before fastening plastic lining or bubble plastic inside the greenhouse – dirty glass excludes valuable light. Cover the ventilators separately. If using single plastic sheeting ensure that a gap of about 2 cm (3/4 in) is left between the glass and the insolation to maximize the double glazing effect.
Make sure that the frames are closed each night to protect any overwintering plants in case of a sudden, unexpected frost. Cover with matting as an added precaution. Take any tender plants out of the frames and into the greenhouse without delay.
Keep a sharp lookout for damage caused by slugs or other pests.
Sow sweet peas without heat and continue to sow hardy annuals. Sow lettuces to overwinter.
Continue to take cuttings of tender perennials and to pot up cuttings that have rooted.
Bulbs, corms, and tubers
Prepare bulbs, corms, and tubers for storage and pot-up lilies for early flowering.
Continue to pick bunches as they ripen. Treat the vines if red spider mite and mildew
November – Greenhouse Job Checklist
Ventilation and watering plants
On sunny days ventilate the greenhouse freely; avoid cold draughts, and close the ventilators fairly early in the afternoon to retain some of the daytime warmth. Dirty glass excludes valuable light, so use warm water containing detergent to wash it.
Keep the greenhouse closed during foggy weather, and cover the plants with newspaper or horticultural fleece if the fog persists. Water all plants sparingly and keep the atmosphere as dry as possible.
Pests and diseases
Whitefly are often troublesome in the greenhouse at this time of year. Treat at the first signs of an attack. It will be too late for natural predators to multiply in sufficient numbers to act as a control. If using a spray, beware of increasing the humidity of the greenhouse too much; fumigation may be more appropriate.
Complete any outstanding potting up early in the month. Annuals raised from seed in September will probably be ready for moving into 13 or 15 cm (5 or 6 in) pots. Pot up sweet pea seedlings. Cuttings of pelargoniums, fuchsias and other plants inserted in September should now be rooted and also ready for potting individually into 8 cm (3 in) pots.
Allow pots of begonias, achimenes, heliotropes, and hydrangeas, which have flowered during the summer and autumn, to dry off. Store the pots under the staging in a cool greenhouse or in a frost-proof shed, but do not allow the compost to become dust dry. Some fuchsias may also be treated in this way. Check dahlias in storage and any bulbs being forced for winter flowering.
Forcing hardy plants
Many hardy plants will flower early indoors if lifted now from the garden and potted into 15-18 cm (6-7 in) pots, depending on the size of the roots. Examples are aquilegia, bleeding heart, polyanthus and Christmas rose which flowers at Christmas if grown under glass. move pots into the conservatory or house when they come into flower.
Begin pruning vines once the leaves have fallen. Plant new vines between now and the end of the year. Although the ideal place is in the greenhouse border, the roots will soon take up the growing space needed for other plants.
An alternative is to plant vines outside and then lead the main shoot through to grow in the greenhouse. Vines succeed with this method, despite the disparity in temperature between the roots and top growth. Dig a hole large enough to spread the roots out well, but do not add manure or fertilizer – vines, figs, grow on poor soil in their native habitat. Cut back the shoot by two-thirds after planting.
December – Greenhouse Job Checklist
Temperature and ventilation
Plant growth is at its lowest ebb this month, owing to the brief hours of daylight. It is a mistake to try to make plants grow more rapidly by raising the temperature, as the resulting growth will be too soft and sappy. Within reasonable limits temperature must be related to light conditions, a minimum night temperature of 7°C (45°F) is adequate for most plants in the average greenhouse.
Open ventilators a little on sunny days but close them again quite early in the afternoon, before the temperature begins to drop, to retain as much of the heat of the day as possible.
Most plants, except those actually in flower, must be kept fairly dry, but do not allow them to dry out to the extent that the soil begins to shrink from the sides of the pot.
In warm greenhouses, if floors and paths need damping down to increase humidity, do this during the early part of the day. This is unlikely to be required where oil or gas heaters are used. Discontinue overhead misting of plants for the time being.
Take cuttings from border perennials, perpetual carnations and late-flowering varieties of chrysanthemums.
Check bulbs and tubers in store for signs of fungal diseases and check on resting chrysanthemums and fuchsias to ensure they have hot dried out.
Pot up lily bulbs and prune any roses you are forcing in containers for early flowers.
Box up rhubarb and chicory for forcing. Check on bowls of bulbs being forced for winter flowering.
Vines should be pruned once the leaves have fallen and the plants are dormant for the winter; if you prune during the growing season, they will ‘bleed’ (lose sap) copiously when cut.
One of the most convenient and space-saving forms of training for a vine in a small greenhouse is the rod and spur system. Once the main stem or the permanent laterals have reached the length you require, cut back all the shoots each winter to just one plump bud.
Now the vine is dormant this is also a good time to propagate from eye cuttings. Make the cuttings about 3 cm (1 1/2 in) long, each with a single ‘eye’ or bud. Making sure the bud is facing upwards, remove a strip of bark on the side opposite the bud, making a shallow cut from halfway down the stem to the base. Dip the cut surface in a rooting hormone, then insert it vertically in a pot of compost. The bud should be level with, or just above, the surface. Keep in a propagator in a moist atmosphere at a temperature of about 24°C (75°F) until it has rooted, then gradually harden off and plant outdoors or in the greenhouse in late spring.