Cheiranthus - Wallflower
(Cheiran'thus)
DESCRIPTION: These are evergreen, semiwoody plants from the Canary Isles, Madeira, and the Mediterranean region. They belong to the Mustard family, Cruciferae. Cheiranthus (Wallflowers) have vertical, branching stems, 1/2 to 3 feet high. In the spring they bear spikes of beautiful and often fragrant flowers. Though they are perennials, they are often treated as biennials and are raised from seed every year. The named varieties of the English Wallflower (C. kewensis) may be primrose, dark red, yellow, orange or purplish. The hybrid, C. kewensis, has brownish-orange flowers that turn purplish. Although the English Wallflowers are a common sight in the spring flowerbeds of Europe, they aren't as recognized in America. The Siberian Wallflower, C. Allionii, may be orange or yellow and are produced abundantly in April and May. Even though the Siberian Wallflower is usually known in gardens as C. Allionii, botanists have the opinion that it's actually an Erysimum. They consider it a product of E. asperum, a native American species. The Siberian Wallflower is hardier than the English kind. The Alpine Wallflowers may be yellow, orange-yellow, or purplish. These are great for growing in well-drained, light soil in the rock garden. Another Alpine variety, C. linifolius, bears tiny, lilac-mauve flowers and is also great for use in the rock garden. This plant is correctly named E. linifolium.
POTTING: After Cheiranthus, which have been started according to the methods described in propagation, are 2-3 inches high and have been planted in nursery beds, they can be transplanted. Where mild winters are the norm, they may be replanted in the fall; where they are severe, they should be replanted in the spring. Protect them in the winter by a light covering of salt hay or evergreen branches. English Wallflowers are not usually hardy in climates more severe than that of Baltimore, Maryland. In colder places, such as New York City, they may successfully be grown by transferring the young plants to cold frames instead of outdoor nursery beds. In the spring, they may be placed in the spots where they are to flower. Throughout the winter, make sure to provide adequate ventilation on every possible occasion. The purpose is to protect them from severe frost without forcing them into premature growth. They will survive 20-degree temperatures and they'll even make it through lower temperatures for a short time. English Wallflowers are great for growing in a sunny, cool greenhouse having a night temperature of 45-50 degrees. Plants that are raised from seeds sown from July to September will bloom in late winter or early spring. C. kewensis is a lovely hybrid for the greenhouse.
PROPAGATION: Seeds can be sown outside, in June or July, in fine soil that has had lime added, if necessary. Sow them thinly and evenly, 1/4 of an inch deep, and cover lightly. The ground between the rows must be hoed often to keep them free of weeds. When the seedlings are 2-3 inches high, transplant them 9 inches apart in rows 15 inches from each other in a nursery bed or 9 inches apart each way in a cold frame. It's important that the soil in the nursery bed or cold frame isn't overly rich with nitrogen and it should be fairly firm rather than loose; firm soil will produce compact well-branched plants instead of loose, straggly ones. It's wise to have compost or other decayed organic material a few inches beneath the surface, the roots will penetrate this instead of spreading widely; a compact root system makes it easier to lift and transplant them successfully. During the summer, keep the beds free of weeds and water them in dry weather. Avoid over watering. C. kewensis is increased by cuttings of young shoots. Seeds of C. Allionii (the Siberian Wallflower) shouldn't be sown before the end of June. If they're sown earlier, they'll start to bloom in the fall and will not provide as good of a display in the spring.
VARIETIES: C. kewensis (English Wallflower), C. Allionii (Siberian Wallflower) and its varieties Golden Bedder and Lemon Queen. C. alpinus, C. Marshallii, C. mutabilis, C. linifolius (also known as Erysimum linifolium). (The latter four varieties are the Alpine Wallflowers.)
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