Gardening in a Cool Greenhouse A Month-by- Month Beginner s Guide Enjoy the year-round gardening experience by starting seedlings, taking cuttings, wintering over plants and growing vegetables in a cool greenhouse. As a greenhouse gardener the main aim will be controlling the greenhouse environment. Each season brings adjustments in heating and cooling requirements. Greenhouse gardening is a continuous learning process. Trying new plant cuttings, seeds and frost sensitive plants brings a challenge and often the pleasure of success. This e-booklet is at your fingertips and will guide you through your greenhouse gardening activities and controlling the greenhouse environment 2008 by Greta Heinen Flowering Plants: Hyacinth, daffodil and tulip bulbs, which were planted last October and now show a fragrant and colorful display in the greenhouse. Bedding Plants: JANUARY Hyacinth Slow growing seedlings like the fibrous begonias and geraniums can now be started on a heated propagating bed. In the greenhouse environment, success or failure depends on the soil. A sterilized potting soil mix is available at garden centers. If you are planning to make hanging baskets in April, planting annual seeds for the baskets is done this month. Annual bedding plants that are started this early will require bottom heat and grow lights. Birch Publishing P.O. 32092 Langley, B.C. V1M 2M3 Canada Telephone: (604)882-0068 Fax: (604)882-8760 Email: inquiries@birchpublishing.com www.birchpublishing.com ISBN:978-0-9698030-3-4 2 Then in April these bedding plants will be ready to transplant into hanging baskets. The bedding plants for hanging baskets are listed in April (Page 8). The maturity date of the plants will determine when to plant the seeds. Tip: I use a dark HB pencil when writing on a plant label because felt pen markings tend to disappear over time.
Cuttings: JANUARY Greenhouse Notes JANUARY Cuttings that were taken in August are now well-rooted and potted into 4 pots. When the cuttings have roots growing through the bottom of the pot, repot to larger pots or containers. Cuttings tend to become spindly, so pinch back by nipping off the growing tip and early buds. New branches will develop and the plant will become fuller. Heating: Keeping a record of the daily minimum temperatures will show if the heater thermostat needs to be adjusted. A cool greenhouse maintains a night temperature of 40-45 F (5-7 C). Max-Min Thermometer Geranium Fuchsia Datura Abutilon Vegetables: Variegated leaf geranium It is still recommended to insulate a glass greenhouse if you haven t done so, since there are still a few months of winter left. Greenhouses built with multi-wall insulated polycarbonate panels will reduce heating costs. Early potatoes, radishes, lettuce and baby carrots can now be started on a heated propagating bed. These vegetables take 120 days to become mature plants. Watering, Fertilizing and Lighting: Cuttings, seedlings and wintered over plants all have different watering requirements. By using a watering can, one tends not to over water. For continued root development 10-52-10, a water-soluble fertilizer, is added to the repotted cuttings. Grow lights provide the additional light for a few hours a day and give the seedlings a boost. A quick test to check if soil cables are working properly is to go into the cool greenhouse in the evening and feel if the soil bed is warm. Greenhouse ventilation is important on the sunny days, even during the winter season. Automatic vent openers will open and manual vent openers must be slightly open as well. The Greenhouse Environment: A circulating fan, on a low setting, is kept on at all times. This will help to move the air and create an optimum greenhouse environment. 3
JANUARY FEBRUARY To prevent diseases, remove any fallen and yellowing leaves. Whitefly can be kept in check by hanging yellow horticultural glue strips and using Safer Insecticide soap. Greenhouse Accessories: Seeds are now available in garden center and nurseries. Consider purchasing a grow light fixture, which adds supplementary light for seedlings and mature plants. A Greenhouse Journal is recommended to keep track of the daily maximum and minimum temperatures in the greenhouse. Writing notes about the plants in the journal will become your best reference book in greenhouse gardening. Flowering Plants: The clivia thrives in the cool greenhouse and will offer a beautiful display of orange flowers this month. Jasmine Polyanthum Bulbs: Clivia Jasmine polyanthum is a very fragrant plant that will only flower if it has a cool period to form flower buds. This is the perfect plant to spend the winter season in a cool greenhouse. In warmer climates you can purchase tuberous begonias this month. The variety of begonia tuber will vary in size. Select a pot that is a size bigger than the tuber. A starter mix of peat is used, but they require bottom heat. Bedding Plants: The listed seeds are the recommended varieties to be sown in February. Seedlings are started on a heated bed or propagator. Two-year Greenhouse Journal Ageratum Calendula Heliotrope Primula Black-eyed Susan Carnations Lobelia Snapdragons 4
FEBRUARY Seed package instructions will state if full light is required. Otherwise they can be covered with plastic to keep in the moisture. Daily checks are made, but as soon as the seeds germinate the plastic covering is removed. Cuttings: Transplanting is done on a continuous basis as cuttings show more active root growth. Abutilon cuttings grow fast and require repotting several times into larger containers. Some abutilon can grow to a 5 height and do not like to be pot bound. Vegetables: Abutilon Cabbage Leek Brussels Sprouts Early Peas FEBRUARY Celery Spinach Early Lettuce Watering, Fertilizing and Lighting: Over wintered plants need very little water and are kept quite dry. Seedlings and cuttings are checked daily and watered only if necessary. Only repotted plants are given a 10-52-10 soluble fertilizer to encourage their root system. The daylight hours are getting longer, but the seedlings still can use a few hours a day of supplementary light from the grow lights. Greenhouse Notes Heating: If you find that only one area of the greenhouse needs to be heated, then drape some plastic to partition off that section. This will save on the heating costs. Lettuce and Herb Seedlings Lettuce, radishes and green onions seeds started now will provide a fresh salad from the greenhouse in a few months. These are some of the early vegetable crops started in the greenhouse for garden planting in covered cloches. On sunny days the vents should be slightly open. Heat rises and the circulating fan will move the air throughout the greenhouse. Circulating Fan 5
Bulbs: MARCH When the tuberous begonias have 3 to 4 of leaf growth, then it is time to repot them into a hanging basket. Canna and gloxinia are summer bulbs that can have a head start and will now be potted in the greenhouse. Bedding Plants: Seedlings started in January and February will now have two sets of leaves and are ready to transplant into trays or seedling inserts. Nasturtium Alyssum Browallia Dahlia Godetia Marigold Nemesia Petunia Portulaca Schizanthus Viscaria Cuttings: The listed seeds can now be started, on the propagating bed for late May planting in the garden. Aster Coleus Dianthus Impatiens Nasturtium Nicotiana Phlox Salvia Verbena Zinnia Some overwintered plants may have new growth and cuttings can be taken again. 6 MARCH The jasmine has finished flowering and this is the time to take new cuttings. Vegetables: French beans can be sown and will remain in the greenhouse during the summer. Beets, broccoli, cauliflower and peppers can also be started and will be ready for garden planting. Watering, Lighting and Fertilizing: Seedlings are watered or misted more frequently. To thoroughly water the seedling trays, set them in a couple of inches in water in the sink. This lets the seedlings absorb the water they require and they will be fine for the next few days. Capillary matting in the trays is very efficient since plants will only draw the water they require. Capillary matting is placed in the bottom of the tray and inserts are set on top of the matting. Then only the matting is wetted down. Capillary matting is a reuseable fiber product. Potted cuttings will benefit from a watersoluble 20-20-20 fertilizer added to their watering requirements. The days are getting longer, but a few hours of supplementary light will still help the seedlings.
Greenhouse Notes Heating: MARCH This is the month when temperatures will start to fluctuate and heating is still required at night. At the end of March, there is a concern that the greenhouse will overheat. Automatic vent openers will take care of the ventilation needs during the day. If you have manual vents, (during the mid day) they will have to be opened. The Greenhouse Environment: Shading is recommended for a glass greenhouse. Seedlings love the light but also require shade. The warmth of the greenhouse will create the perfect environment for pests and diseases. Horticulture yellow sticky strips will help to control whitefly. Greenhouse Accessories: Shelving attached to the sidebars will add the much-needed growing space inside the spring greenhouse. Bulbs: APRIL This month you may still be transplanting the tuberous begonias, canna and gloxinia. Substantial leaf or shoot growth will determine when to transplant these bulbs. Begonia Leaf Growth Bedding Plants: Annuals seedlings are often small and come up in a dense mass. Thinning out will give them more room to become stronger seedlings. When the second set of leaves has developed, they can be transplanted. Keep the transplants on the propagating bed for a day or two and then move them to the benches. They will no longer require bottom heat. Zinnia, Nemesia and marigold seeds can still be sown this month. Cuttings: Some cuttings are ready to be transplanted to permanent containers and hanging baskets. Plants will be reaching for light and can become spindly. Pinching back these plants encourages, fuller leaf growth. Hanging Baskets: Geraniums, fuchsias, heliotrope, impatiens, nemesia and petunias are proven plants to use in hanging baskets. 7
Geraniums APRIL These are easy to make and offer a beautiful display of color. APRIL If you did not start the annual bedding plants in January for hanging baskets, you can purchase basket stuffers, or small bedding plants. Planting them in baskets this month will guarantee a full-grown hanging basket display by the end of May. Large moss hanging baskets use a wide selection of annual plants, with many inserted along the sides of the basket. Moss Hanging Basket The following are some plant varieties for mixed hanging baskets. Creeping zinnias Lobelia Bacopa Swan River Daisy Heliotrope Trailing geraniums Marigolds Trailing Petunias Calceolaria Fuchsias Verbena Vines and ivy add fullness and length to the basket. Nepeta Variegated Ivy Lamium Silver nettle vine Variegated Periwinkle Lotus Vine These vines and ivy can be wintered over in the greenhouse. It is important to select a location for the hanging basket and choose the plants according to shade or sun. Vegetables: April 1 st is always the date I sow the long English greenhouse cucumber and tomato seeds. These plants will remain in the greenhouse for the summer months. The first crops of lettuce and carrots are now ready for harvesting Garden Vegetables: First Crop of Lettuce The garden vegetable plants need to become acclimatized or hardened off. They can be set outside in their pots, but on cold nights place them in a protected area. Watering and Fertilizing: Due to more sunny days, frequent watering become necessary. A balanced soluble fertilizer 20-20-20 is added to the water and given to the plants once a week. Cacti have been dormant all winter and this month slowly start watering these plants to force flowering. 8
Greenhouse Notes Heating: APRIL Day temperatures are warmer but in some areas night temperatures can still drop drastically. Still keep the heater set for a night temperature of 40-45 F (5-7 C). It is recommended that hanging baskets have a night temperature of 50 F (10 C). Based on experience the greenhouse can have a lower night temperature, but the plants will grow a bit slower. When they go outdoors, they quickly catch up in growth. Roof and side vents are open longer especially on warm days. If the greenhouse door has a glass panel that rises, it will remain open during warm days. Automatic exhaust fans will be in use more starting this month. Exhaust fans require an intake of air, which can be by opening doors and louvers, but it is better to use an intake shutter. APRIL The diffused sunlight transmission through polycarbonate panels prevents plant damage and burning. This is the busiest month in the greenhouse and daily attention is given to the many varieties of plants. The circulating fan is now set at a higher speed, which makes quite a difference in air movement. This helps to control the fluctuation of daytime temperatures within the greenhouse. Greenhouse Accessories: An exhaust fan and intake louver, during the spring and summer months, will help stabilize the greenhouse daytime temperatures. Eyebolts are fastened to the roof bars to carry the hanging baskets. Exhaust Fan The Greenhouse Environment: In glass greenhouses the insulating material is removed and the shade cloth is installed to protect the plants from burning. Intake Shutter 9
Flowering Plants: MAY This is the month when you will see, enjoy and sometimes be in awe of the success of greenhouse gardening. There are colorful displays of the annual bedding plants and the fragrance and fullness of the hanging baskets. Bedding Plants: Most annual bedding plants will be planted in the garden after May 20 th. In the cooler climate; this takes place in early June. Plants need a period of acclimatizing or hardening off before they are planted in the garden. Three weeks before garden planting, the greenhouse heating and venting requirement will change. (See heating and ventilation on page 11). One week before the garden planting takes place the bedding plants and hanging baskets are moved outdoors and placed in protected areas. If there are still a few cold nights, an openended clear plastic canopy will protect the plants. Cold frames are ideal for plants to get acclimatized before being planted into the garden. 10 If the spring is cold and wet, it is recommended to wait an extra week before garden planting. MAY Plants getting acclimatized Looking ahead? This is the month to sow pansy and viola seeds, for the fall garden. Cuttings: There are no cuttings this time of year, unless you come across a usual plant that you want to add to your greenhouse collection. Vegetables: Tomato and cucumbers that will remain for the summer in the greenhouse are now potted in their permanent pots or grow beds. It is important to hang up the support strings or twine for the plants to climb up. All the garden vegetable seedlings are moved outdoors to harden off and then to be planted in the garden. Watering and Fertilizing: All plants will need a daily watering. Fertilizing the plants will now increase to twice a week but only after they have had a thorough watering. Tip: After the plants are watered, an additional light watering is given, with a watering can containing 20-20-20 fertilizer.
Greenhouse Notes Heating: MAY Night heat will no longer be necessary, but in case of a cold spell in early May, it is best to keep the heater at 45 F (7 C). MAY May is the start of hot sunny weather and the greenhouse air will become dry. To increase the humidity wet the benches and floor. In greenhouse gardening terms this is called damping down. With the warmer temperatures the roof vents and side vents will remain open all day. The circulating fan will assure the constant movement of air in the greenhouse. Leaving the greenhouse door open during the day will help cool the greenhouse. The daytime temperature reading on the maximum-minimum thermometer will show if more ventilation is required. The Greenhouse Environment: At the end of the month most plants have left the greenhouse, and this is the perfect time to clean the inside of the greenhouse. For glass greenhouses a good cleaning solution is hot water with a disinfectant of Lysol, Pinesol or household bleach. Benches, shelving, plastic trays and pots are also cleaned. The Spring Greenhouse To clean polycarbonate greenhouses and protect the panels rinse the greenhouse with lukewarm water. Using a mild soap and soft cloth wipe down but do not scrub the panels. Rinse the greenhouse again and wipe dry with a soft cloth. 11
Flowering Plants: Watering has increased for cacti and they are now starting to bloom. JUNE The Christmas cactus will now go dormant and are taken out of the greenhouse and placed in a shaded garden area for the summer months. Bedding Plants: Pansy and viola seedlings planted last month are ready for transplanting. Greenhouse Vegetables: Tomatoes: Small shoots, known as suckers, grow just above the leaf joints and must be removed. To pollinate the tomatoes and cucumbers, daily tap the wire or string supports. Cucumbers: Cucumbers produce on the female flower. It is important to remove the male flowers and non-flowering side shoots. The cucumber plant is staked and the vines are trained to climb along wire or twine hanging down from the roof bars. Watering and Fertilizing: The greenhouse tomatoes require daily watering, which is regulated according to the weather and greenhouse temperature. JUNE The amount can vary from one cup on dull days to a half gallon on sunny days. Feeding or fertilizing tomato plants takes place after flowering and the fruit begins to form. A liquid tomato fertilizer will provide the nutrients to encourage fruit development. Greenhouse cucumbers prefer smaller doses of frequent watering. However, one must be cautious not to overwater these plants. Once the fruit has formed, the cucumbers are also fertilized with a liquid tomato fertilizer. Greenhouse Notes Vents, louvers and the door will be open during the day. The Greenhouse Environment: Damping down the inside of the greenhouse will not only increase the humidity but also bring down the temperatures. Whiteflies are attracted to the yellow horticulture sticky strips. The strips are hung close to the plants. 12
House Plants: JULY Potatoes: JULY Houseplants can be placed in a shaded area of the greenhouse and will get refreshed from the high humidity. Greenhouse Vegetables: Tomatoes: This month the harvesting begins for the tomato crops. Tomatoes will need to be controlled or they will take over the greenhouse. When the plant has seven trusses that have set, the growing tip is pinched out at two leaves above the top truss. Cucumbers: The best time to harvest cucumbers is when they have reached a good length. They should never reach full maturity and start to yellow. The cucumbers also need to be controlled so that when the plant reaches the roof of the greenhouse the growing tip is pinched out. To harvest new potatoes at Christmas, now is the time to set out some potatoes for sprouting. Watering and Fertilizing: Depending on the weather, watering may increase to twice a day. Even though tomatoes and cucumbers are ready to harvest a regular feeding with liquid tomato fertilizer is still required for next month s crops. Greenhouse Notes During an extreme hot spell an electric house fan will help force more air movement and bring the inside greenhouse temperatures down. The Greenhouse Environment: Damping down the greenhouse twice a day is necessary, especially in the hot summer weather. Pests love the summer in the greenhouse. Using safer soap and yellow horticulture strips will help prevent an outbreak. If an outbreak occurs, determine what pest or disease is present and the garden centers will provide the correct spray. 13
Cuttings: AUGUST Since all flowers are at their peak, this is the best time to take cuttings from all your favorite garden varieties. Tip: To take cuttings make a sharp cut just below the node of the branch. AUGUST Extra support may be required to carry the weight of the plants. Cucumbers: The cucumbers are now at their peak and require daily attention. Potatoes have sprouted and are planted into large pots for winter crops in the greenhouse. Datura Cutting Next Years Datura Watering and Fertilizing: The following plant cuttings do well in the cool greenhouse environment. Geraniums Fuchsias Abutilon Heliotrope Lantana Datura August is also the month to collect seeds from the annual bedding plants. These seeds are placed in a paper bag to dry. Once they have dried, the seeds are stored in glass jars in the fridge. Verbena Vegetables: Tomatoes: Irregular watering is the cause of cracks in the ripening tomato. Tomatoes and cucumbers are watered daily and fed with tomato fertilizer on a regular basis. Greenhouse Notes Heating: In the colder climates, check your heater and get it ready for the winter season, since an early frost is possible at the end of the month. In the cooler climates if the night temperatures are starting to drop, the roof vents will need to be closed at night. The Greenhouse Environment: There is more humidity in the greenhouse due to damping down and this can create mould. A preventative measure is to keep the ground area clean from leaves, fallen fruit and flowers. 14
Bulbs: SEPTEMBER September is the month to plant bulbs in pots for the December and January greenhouse display. These pots of hyacinth, narcissus and small tulips are kept in a cool storage area for eight to ten weeks. When the first frost hits the tuberous begonias leaves, the tuber is removed from the pot or basket. These tubers are cleaned and stored in a cool area until February. Cuttings: Begonia Basket August cuttings have developed roots and are ready to be transplanted into pots. More cuttings can be taken from frost sensitive plants, but they will require bottom heat. A good cutting mix is two parts perlite and one part peat. I have had great success using peat pellets for cuttings. Vegetables: Tomato and cucumber plants have finished cropping and are removed from the greenhouse. Winter lettuce can be started and is an easy plant to grow in the cool greenhouse. SEPTEMBER Wintering Over Stock or Parent Plants: Depending on your climate the frost sensitive plants are pruned or cut back and brought into the greenhouse. In the coastal warmer climate this can be done in October Frost sensitive plants are brought in when the night temperature is lower than 40 F (5 C). Ivy and vine plants are taken out of the hanging baskets, cut back and repotted into 4 pots. These will winter over and next April will be planted into hanging baskets. Cuttings can be taken from the osteospermum, and the parent plant is cut back and wintered over in the cool greenhouse. Osteospermum Tip: Stock plants are pruned back just above the node on the branch. This is where the new growth will start. Watering: Plants are now moving into their dormant stage so the watering requirement is reduced. Greenhouse Notes Heating: The heater is now set at 40-45 F (5-7 C). 15
SEPTEMBER Bulbs: OCTOBER The roof vents will still need to be opened on sunny days. Movement of air inside the greenhouse is always necessary. This time of year the circulating fan is set on a lower speed. The Greenhouse Environment: Now is another opportunity to clean the greenhouse thoroughly before the frost sensitive plants are brought in. As a preventative measure spray with Safer Soap all plants that come from the outside garden into the greenhouse. For glass greenhouses the shade cloth is removed and a plastic liner for insulation is attached inside the greenhouse. Special Note: Hibiscus Like last month, bulbs are placed into pots or containers and stored in cool area. In February you will enjoy the color and fragrance that these bulbs have to offer. Cuttings: The roots of the previously taken cuttings are now developed. These cuttings are planted into 4 pots for the winter season. Late cuttings can still be taken from the frost-sensitive plants. Lantana Pruning Stock or Parent Plants: In the warmer climate plants remain outside longer, but this month the frost sensitive plants are ready to be cut back and brought in. Watering: Tip: The morning is the best time to water plants in the greenhouse. Bougainvillea Passion Flower The bougainvillea, hibiscus and passion flower are frost sensitive plants, but do not winter over in a cool greenhouse. These plants require a different greenhouse environment with a warmer night temperature. The cuttings on the heated propagating bed will require watering. Once the cuttings are repotted they will go dormant and develop their root system. Dormant plants will not be actively growing and will therefore require less water. 16
OCTOBER NOVEMBER/DECEMBER The Christmas cacti are brought in and slowly start watering to encourage the formation of buds for a Christmas display. All watering is stopped for all the other cacti plants and they will remain dry during the winter months. A light misting is done if the cacti leaves start to shrivel and dry up. Flowering Plants: In December the Christmas cactus and bromeliads are in bloom. Bulbs: Bulbs that have been in cool storage will now show some growth. They are brought into the greenhouse and will provide a colorful display during the Christmas season. Bromeliad Cactus in the Winter Greenhouse Greenhouse Notes Heating: Minimum temperatures are checked daily, since heating thermostat settings will often require adjustment. On sunny days there can be a heat build up inside the greenhouse. To eliminate this the constant air circulation with a small fan will force the heat to rise and open the automatic roof vents. Cuttings: Cuttings will continue to be potted when the roots develop. Rooted cuttings are placed on the bench. Keeping them on the heated bed will force active leaf growth instead of root development. Vegetables: Lettuce and potato will be ready for harvesting later in December. Watering: Watering the dormant plants may only need to done once a week or every ten days. 17
NOVEMBER/DECEMBER In the rainy climates the greenhouse humidity is high. Caution is taken not to splash water on the benches or floor. GREENHOUSE LIGHTING INFORMATION The tulip, narcissus and hyacinth bulbs in cool storage will be brought into the greenhouse for the January display and they will require some watering at this time. Greenhouse Notes: Heating: To help control heating costs, daily check the minimum temperature reading to make sure that the heater does not go higher than 45 (7 C). One area of concern can be condensation inside the greenhouse. The main cause is a lack of air circulation. The greenhouse requires very little ventilation; the roof vents will be slightly open only on sunny days. Greenhouse Accessories: Seed catalogs start arriving this month. Some catalogs offer seeds for growing under glass or in a greenhouse. There are many greenhouse grow lights available in the marketplace. Over the years I have tested several of them, but in the end my preference is the florescent grow light fixture. An efficient grow light fixture is 1.2 meters (4 ) long and draws 40 watts of electricity. Reflectors on the fixture will direct the light to the plants. One florescent tube warm white and one cool white give a balanced distribution of light for the plants. The height of the fixture is 30 cm (12 ) above the mature plants, 20 cm (8 ) above cuttings and 14 cm (6 ) above seedlings. 18
HOW TO BUILD A HEATED PROPAGATING BED A Note From The Author I hope you enjoy year-round gardening in a cool greenhouse as much as I do. Size: (56 cm) 22 x 22 1-3 m (10 ) soil cable Soil cable is spaced (11 cm) 4 ½ apart A soil cable propagating box can easily be constructed by building a wooden box six inches high around two flats. On the solid bottom put two inches of sand, and lay the soil cable on this sand in looped form. Cover this soil cable with two more inches of sand and place the flats or inserts on top. The heat travels through the sand and provides an even heat to the flats or inserts and pots. As you can see my greenhouse has a wide selection of companion plants and they all do well in the same environment. This e-booklet is based on my many years of expertise in the field of greenhouses and greenhouse gardening. Greta Heinen Automatic soil cables have a preset thermostat of 21 C (71 F). These are available in 3 m (10 ), 5 m (17 ), 8 m (26 ) and 10 m (33 ). Heated propagating boxes can be made in any size and soil cable length is determined by the square footage of the growing area multiplied by three. 19