Growing Roses in the Greenhouse and Recommended Varieties
Roses grown in pots in a cold greenhouse reveal a pristine beauty that is rarely, if ever, seen outside. Both blooms and foliage attain a perfection that is virtually impossible in the open, where theare always at the mercy of the elements. In a cold greenhouse the first usually appear about a month earlier than those outside.
The greenhouse should have a winter temperature of about 45° F. (7° C.) at night, and at no time should the temperature rise above about 60° F. (16° C).
In October, prepare 10-in. pots by placing crocks in the bottom to facilitate, and charcoal to sweeten the planting mixture. Follow this with a compost of three parts moderately heavy loam and one part well-rotted manure, and add two handfuls of bone meal. Then dig up trees of the chosen variety, or buy them from a nursery. Trim the roots so that they can spread comfortably in the pot, and plant the roses so that the level when pressed down firmly is not less than 2 in. below the top of the pot.
Stand the pots in a sheltered corner out-of-doors; shorten any extra long stems to prevent the bushes from blowing about and loosening in their pots before the roots are firmly established.
Bring the pots into the greenhouse in December, and keep them bone dry until the foliage has dropped off, usually in two to three weeks. Then prune really drastically to only two buds from the base of each main stem. Failure to do this will result in thin growth and mediocre flowers.
WATERING AND FEEDING
Water thoroughly after, but give no more water until fresh growth appears. Then water once a week, and when the roses are growing well, more frequently still; never let the pots dry out. If in doubt, rap the side of the pot with a wooden hammer or with the knuckles; a dull sound means that the soil is still damp, and a hollow ring indicates that watering is essential. Remember that a cracked pot always produces a dull sound.
Feed with a proprietary fertilizer from the end of March, following the manufacturer’s directions. The frequency of feeding will depend on the progress of each plant, but every seven to ten days is usually sufficient. After the first flowering has ended, transfer the pots outside and water occasionally during dry spells. Re-house the trees in December, after first removing the top inch or so of potting mixture and replacing it with fresh similar material. The first year’s treatment can then be repeated.
PESTS AND DISEASES
For the treatment of, aphids, thrips and caterpillars see Roses.
Another potential pest for the greenhouse rose is red spider. Leaves attacked by red spider mite assume a mottled, yellowish appearance on the underside, and fall prematurely. Liquid derris gives some control, but current literature from leading insecticide manufacturers should be consulted for the most up-to-date treatment.
The following varieties are reliable for large, specimen blooms under glass:
Christian Dior, crimson.
Eden Rose, deep pink.
Ethel Sanday, yellow and apricot.
Gail Borden, light pink and pale yellow.
Margaret, light pink.
My Choice, salmon-pink and buff-yellow.
Paris Match, deep pink.
Peace, yellow and cream.
Pink Favourite, deep pink.
Prima Ballerina, deep pink.
Silver Lining, light pink.
Medium-sized, decorative blooms are:
Baccara, deep vermilion, grows far better in the greenhouse than in the garden.
Lady Sylvia, flesh-pink.
Mrs. Sam McGredy, scarlet and orange.
Spek’s Yellow, deep yellow.
Super Star, vermilion.
Wendy Cussons, deep pink.
Anna Wheatcroft, rosy-salmon.
Celebration, light salmon.
Dickson’s Flame, scarlet.
Flamenco, deep pink.