Now that the outdoor garden requires a more significant part of your time don’t neglect your greenhouse.
Greenhouse gardening can be more than a winter proposition, mainly since the initial investment is considerable. It would be a shame not to use the greenhouse the year around and get the total return of summer fun and flowers without additional cost.
Many plants cannot be brought into good bloom without the protection from wind, rain, and direct sunlight which a greenhouse provides. They include some of the most beautiful flowering plants and shrubs which grow.
Other plants must be grown under glass and carried on through the summer if they are to flower next fall and winter.
Among the summer flowering plants which you will enjoy are:
- Columnea gloriosa, with tubular scarlet and yellow flowers;
- Mexican orange (Choisya ternata), with white orange-blossom flowers;
- Black-centered, daisy-flowered Dimorphotheca ecklonis or cape marigold;
- Shamrock pea (Parochetus communis), with blue and pink pea-shaped blooms;
- Tuberous rooted begonias; flameflower (Talinum calycinum), with vivid pink flowers;
- Star jasmine (Trachelospermum jasminoides), with fragrant white blooms;
- and many, many more which will fill your greenhouse with color, beauty and fragrance during the summer.
I particularly enjoy growing one plant and its glory bower (Clerodendron thomsonae). A reader who spent much time in the Philippines tells me it is also called Secreto de Amor. This clerodendron is a climber who makes a grand show from late spring until fall.
The flowers appear in large clusters of rich crimson, set off by white calyxes. While the plant will grow to 10’ feet, it is suitable for the small greenhouse and can be brought into flower when only 18″ inches high in a 6″ or 7″ inch pot. I have had no trouble controlling an excellent specimen within 3′ or 4′ feet.
Young clerodendron plants are available from several suppliers. It is also possible to root cuttings of half-ripened wood any time of the year. I have also grown Clerodendron speciosissimum which is a shrub with orange-red flowers.
This variety, however, spreads too much to be worthwhile in small quarters. It would be better in a medium or larger-sized greenhouse.
Clerodendron Prefers Coarse Soil
Clerodendron does well in coarse, composted soil. It should be fed every ten days during the early spring growing season with a complete liquid fertilizer. This feeding will produce vigorous growth and large blooms because the blossoms come on new development. Hardening off is not necessary for flowering.
Never let these plants go for want of water, however. After bloom, clerodendrons are best kept on the dry side until January with just enough soil moisture to prevent wilting of the leaves. A temperature of about 55° is suitable during the winter when they can be given a rather severe pruning.
Few insects attack the plant, but mealybug may appear in the leaf axils of old-growth. Aphids sometimes attack young plants.
The shading on your greenhouse may again need attention. If you use whitewash, an additional coat may be needed to increase the density. Slat shading may need supplementing with cheesecloth for more tender plants which show signs of burning from the hot summer sun.
Cuttings of midseason and late chrysanthemum varieties should be started this month. Select slips from clean, insect, and disease-free plants. After a 21-day rooting period, set the cuttings directly in greenhouse benches or pots sunk to the rim in the garden until fall.
The giant anemones and ranunculus, which you see at flower shows, are grown from selected seeds. Blooms from corms or tubers never reach such heights of perfection. I have been told that this is because the tubers we buy have not been properly hardened off after flowering, as with most other fleshy-rooted plants.
Naturally, the very best blooms come from new plants started from seed each year.
Snapdragons On June
June is also the month to sow snapdragons for flowers from next November on. I like to grow snapdragons unpinched on a single stem, setting the plants as close as 6″ inches. The second crop of flowers is produced on the side shoots after the first blooms are cut.
Cyclamen is started from seed in June but takes 18 months to reach the flowering stage. So don’t attempt it unless you are prepared to care for the plants over a long period. Cyclamen seed should be germinated at a cool temperature; 50° degrees is optimum.
I find that the roots do best in the cellar, but you must bring them into the light after the first shoots appear. The young plants require plenty of water and dense shading from the hot summer sun.
In the fall, you may prefer to buy young cyclamen plants in 3″ or 4″ inch pots from a nursery, transferring them to 6″ and 7″ inch pots as necessary. Such plants will bloom all winter long, giving you good flowers for cutting.
Tubers of calla lilies that have flowered should be dried off now. A suitable method is to place the pots on their sides under the plant benches if there won’t be too much water dripping from the benches. Syringe lightly to keep the tubers from shrinking.
44659 by Ernest Chabot