The relationship between cold frames and gardens increases as the days become longer and the sun warmer. In fact, the chief purpose of the cold frame in spring is to prepare plants for outdoor conditions.
Once they recover from the initial transplanting within the frame, hardier plants, such as cabbage and broccoli, should be gradually given full exposure.
Providing Exposure
Remove the sash altogether on warm days. It can also be left off at night unless there is a danger of frost.
After a few such nights of exposure, these hardy plants are ready for the garden and will be unharmed by light frosts.
The more tender plants—tomatoes, peppers, and eggplants—cannot be given full exposure just yet.
Close their sash early in the afternoon while the air is still warm. However, it is not practical to remove the sash completely, even on warm days, as the wind may damage the plant tops.
Always water the plants in the forenoon so the foliage will dry by evening. Ventilation at this stage is very important.
Good Method of Raising The Sash
A good method is to raise the sash at the long side rather than at the ends. Remember to raise it at the side opposite to the wind so that there is no direct draft into the frame.
Space left by the hardier plants can now be devoted to more tender varieties or for sowing seeds of half-hardy or tender annuals, depending upon the region.
In the vicinity of New York, the half-hardy annuals can be sowed right in the garden.
They include:
- Phlox drummondii
- Scabiosa
- Spider-flower
- Basketflower
- Centaurea
- Rudbeckia
For the tender annuals, they are the following:
- Zinnias
- Cockscomb
- Verbenas
- Lobelias
- Everlasting
- Asters
- Dahlias
- Petunias
They must be thinned out as seedlings or transplanted within the frame to await warmer weather.
Tomato seeds can also be sown directly in the cold frame, but in northerly regions, the hotbed will be needed for them, at least at night.
Starting Vine Crops
Early crops of melons, cucumbers, and squash can be started in the frame 4 to 5 weeks before the usual time for outdoor seed planting.
Sow the seeds in the 3-inch plant bands mentioned last month, with several seeds in each band.
Later, all but one seedling should be removed if the seeds of these vines are started too far in advance of the normal time.
The plants may become cumbersome to handle, and growth checked in the move to the garden.
Outdoor Sowing And Planting Season
With the beginning of the normal outdoor sowing and planting season, the cold frame can be used for other operations.
Gladiolus corms planted in pots and kept in the frame for a couple of weeks will produce early flowers in the garden.
Tuberous Begonias
Tuberous begonias can be started by placing the tubers, concave side up, on moist peat.
When pink shoots appear, put the tubers in 4- or 5-inch pots or plant bands. They can be moved outside later.
If you have sufficient space, move chrysanthemum plants from the garden to the cold frame.
Root Cuttings
When young shoots, 2” to 3” inches long, appear on the plants, make cuttings of them. Dahlias can be handled in the same way, although they require more time.
Root cuttings in clean moist sand, preferably in a flat; keep sand moist until roots are formed, usually in about three weeks.
Rooted chrysanthemum cuttings can be planted directly in the garden. Dahlias are best set in small pots and kept in the frame until late May or June.
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