Cold Frame Gardening

Cold frame gardening and a hotbed is big in the month of March. This is the time when seeds and cuttings are started for the garden’s plant supplies and extend your gardening season.

Utilizing Space Efficiently

In order to utilize cold frame space efficiently, sowing and transplanting operations must be planned to fit your particular climate and the kind and quantity of plants or crops you need for an early spring.

For example, sowing of hardier, fast-growing vegetables and flowers in the coldframe should be timed so the plants may be transplanted into the vegetable garden or flower garden to make space in the cold-frame for the more tender things sown previously in the hotbed or house. These must be kept growing in the cold frames for another four to six weeks.

The timing factor is not as critical when there is ample cold frame or hot bed space available. Then many plants can be set in pots and grown on without crowding. It’s the minimum space that needs care in planning. Plants must be transplanted when they reach the proper stage or they will become stunted from being crowded in seed rows.

Cold Frame & Hotbed Plan

The plan on this page is offered as a guide for the use of a three-sash frame of 3 x 6 foot standard glass window sash. This covers an area 6 x 9 feet. One section, a single 3 x 6 foot frame, is used as a hotbed. Or, you can dispense with the hotbed and raise the more tender material in the house. Operations are based on conditions prevailing around New York City; farther north. allowances must be made for different sowing and planting dates.

Cold Frame Gardening And Hot Bed Diagram

drawing of a cold frame and hotbed garden
The above set of frames, covering an area 6 by 9 feet, uses three standard 3×6 foot sash to help extend your gardening season. It can be a raised bed or dug into the ground. The frame at left is electrically heated with a heating cable, the other two are unheated coldframes relying on solar energy.

The planting plan is based on sowing half rows of each variety. Where more than one variety is planted, the different kinds are indicated by 1, 2 and 3. Varieties themselves are a local problem; for the names of those best suited to your locality, consult your state agricultural experiment station or other local authority.

Planting dates are for the vicinity of New York City. To prevent crowding, seedlings are thinned or transplanted. Those from the coldframe can generally go directly in the garden; those from the hotbed to the transplanting frame or spaces in the coldframe.

Cool-Weather Crops

Cool-weather crops like cabbage, broccoli, lettuce, leeks and onions, suggested for February sowing in the hot bed, can be sown in the cold frame during the beginning of March – the only heat coming from solar energy.

In addition to these, you can also sow sweet peas, centauria (cornflower) and annual larkspur The vegetables will be ready for transplanting in three to four weeks In about six weeks from date of sowing, about mid-April, they should be ready for the garden, provided they have not been coddled in a heated frame with a heating cable.

Since larkspur is not easily transplanted. it is best sown in small pots or 2-1/2-inch plant bands. Plant bands are made of light wood or other material, are square and open top and bottom. They may be fitted closely together in flats or a coldframe and filled with soil, making separate compartments for seeds end seedling transplants. Roots will eventually fill the whole band. At transplanting time, the plants are lifted out completely with roots intact – peat pots are also an excellent way to go.

Larkspur and other annuals can be transplanted directly into the garden. If the weather is too unfavorable and the growing season is not really underway, wait another week or plant them out with a little protective covering.

Tomatoes and celery are transplanted from the hot beds to spaces left by the hardier material in the coldframe. Leave a few tomato plants in the hotbed for larger plants. Eggplants and peppers are transplanted within the hotbed – these need more warmth at night for a longer period.

Hardening Off

Hardier plants, kept in a coldframe by themselves, can be “hardened-off” – that is, gradually exposed to full outdoor conditions prior to setting out. This is accomplished by keeping the sash off during the day and gradually continuing this into the later evening until it is removed altogether as cold weather moves out. How fast the plants are hardened off will depend upon the weather.

As an alternative plan, sow more seeds of fewer kinds of plants and, instead of transplanting, thin out the plants to 3 inches the rows and allow them to grow large enough for outdoor planting. This eliminates one transplanting operation but uses more space, especially in the hotbed.

Soil Mix and Planting

The soil mixture for sowing seeds, leveled off and tamped fairly firm can be a bagged soil mix or make your own mixture of 3 parts garden loam and 1 part peat moss. If the soil is “heavy” add some sand to improve drainage. The rows can be 3 or 4 inches apart. When seedlings are transplanted early, the 3-inch spacing is suitable. A 3- or 4-inch board is handy for keeping the rows straight and the edge makes a good guide for marking seed rows when a pointed stick is drawn against the board. Just barely cover the seed and water with a fine spray. The soil should be moist but not soaked.

The glass of the hotbed sash can be covered with burlap, newspaper or other material until the seeds sprout. Or, you can save electric current by covering the soil during the day before the seeds germinate and allowing the solar energy of the sun to heat the frame interior. With the latter plan, however, the protective, insulating cover should be put on at night over the glass. The coldframe, having no bottom heat, depends on sunlight to heat the soil sufficiently to start germination. Newspapers are laid over the seeds and the sash kept on. As soon as sprouting begins, remove the paper for light is then needed.

Essential Ventilation

After seeds have sprouted, ventilation is essential. Watch the thermometer inside the frame and keep the temperature as close to 70 degrees as possible. The temperature will rise rapidly on sunny days. Ventilate by lifting the sash on the side opposite the direction from which the wind is blowing. This avoids drafts on the little plants. The young seedlings will require shade during the bright part of the day for a time but they should be given all the light possible in the morning and afternoon.

When evening covering is needed, it should be put on while the sun is still heating the interior in order to trap and hold the heat throughout the night. Water, too, will be needed; sometimes not over the entire area but in spots where the soil has dried out. All watering must be done in the morning when the temperature is rising so that the foliage of the seedlings will be dry when the covering is replaced in the evening. This is important in preventing diseases.

When the seedlings are well through the soil, a little shallow cultivation between the rows is beneficial and also tends to ward off diseases.

Tips To Improve Your Plant Care
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