Fact sheet: Crocosmia
The genus Crocosmia belongs to the Iris family (Iridaceae) and contains eleven or so species of cormous perennials, most of them native to southern and tropical Africa. A corm is a swollen stem base that is modified into a mass of storage tissue. A corm is technically different from a true bulb because it does not have visible storage rings when cut in half. Gladioli, crocus and autumn crocus are other examples of plants that grow from corms.
The name crocosmia comes from the Greek words for saffron (krokos) and smell (osme), because dipping dry crocosmia flowers in water apparently releases a saffron-like aroma. Common names for crocosmia are coppertips and falling stars. Other names for hybrids and cultivars include montbretia, antholyza and curtonus. Crocosmia crocosmiiflora (montbretia) dates from the 1800s. The Lemoine nursery in France named this natural hybrid after the botanist Antoine François Ernest Conquebert de Montbret, who accompanied Napoleon on his 1778 Egyptian campaign.
Montbretia, along with Crocosmia masoniorum (Crocosmia ‘Marcotijn’), and some forms ofCrocosmia pottsii (including ‘Red King’ and ‘Red Star’) spread readily. There are approximately 400 crocosmia cultivars. Just because a few cultivars have shown invasive tendencies, gardeners should not shy away from growing any of them. That would be a sad and unnecessary deprivation, indeed; so do yourself (and the local hummingbirds) a favor and include crocosmias in your garden. The named cultivars are probably less invasive than the straight species.
Why grow crocosmias? Few diseases or pests (including slugs!) seem to trouble crocosmias. Humans and hummingbirds alike appreciate the red, orange and yellow crocosmia flowers. During crocosmia’s typical mid-summer to fall bloom period, other flowers have finished blooming or are looking tired. Crocosmia flowers last well in the garden and in the vase, especially if properly conditioned in the latter case. Cut stems when the first few flowers at the bottom of the spike are just opening. Strip the leaves from the stems. Recut the stems and stand the flowers up to their blooms in tepid (100-degree) water, in a cool dark place. Leave them there for 48 hours, letting the water cool off during the conditioning. Experts say that without this deep and lengthy water immersion, cut crocosmias will not last as long as they could.
Crocosmia leaves, two to three feet in length, are generally ribbed, but sometimes pleated, and always sword-shaped. Leaf color is usually mid-green, but some varieties sport pale green or even brownish-green leaves. Even when crocosmias are not in bloom, their leaves offer contrasting form and color among other perennials. In addition to being good border plants, many crocosmias work well in containers. If grown in pots with plenty of organic matter and fertilizer, montbretias bear much larger flowers than when they are grown in garden beds.
Crocosmias are easy to grow in USDA zones 6 through 10, where they are hardy. You might find them growing in pots in nurseries, but we recommend planting corms rather than plants. In early spring, seek out firms that have a good selection of summer-blooming bulbs. Look for corms at local garden centers, nurseries, farmers’ markets, and on the internet. Ask gardener friends who need to divide a clump to share some with you. Select a site in full sun (part shade in hot areas) with moist, well-drained, slightly acidic soil of average fertility. Crocosmias should be planted at the time when you plant dahlias or begonias, when the danger of spring frost has passed. Set corms 6 to 8 inches apart, at a depth of 3 to 5 inches. Group a dozen corms of the same type of crocosmia for the best effect. You may not get blooms the same year that you plant the corms, but you can count on blooms during the following summer. Try growing crocosmias behind short dahlias.
Plan to lift and divide congested clumps of crocosmias in spring, just before growth starts. If you find offsets at the base of the main corm, remove and plant them or share them with other gardeners. Don’t remove leaves after plants have bloomed – let them protect the bulbs and emerging shoots from frost.
Crocosmia hybrids are numerous, but not always easy to find. Crocosmia ‘Lucifer’ (Lucifer Montbretia) is worth seeking out. It was bred by Alan Bloom of Blooms of Bressingham, Norfolk, UK, around 1966 and is a Great Plants Pick. Flower stalks 4 to 5 feet in height bear brilliant scarlet upturned nectar-filled tubes. Consult www.greatplantpicks.org for more details about ‘Lucifer,’ which is perhaps the most well-known and most frequently sold crocosmia of all time. Here in southwestern Washington it is clearly a hummingbird magnet.
Crocosmiax crocosmiiflora ‘Carmine Brilliant,’ a late 19th-century hybrid, is characterized by a generous number of small, deep red blooms with yellow stamens. Flower stalks are 30 inches tall on this relatively hardy (zone 6) plant.
Crocosmia x crocosmiiflora ‘Emberglow,’ hardy to USDA zone 5, bears red flowers on 40-inch stems.
Crocosmia x crocosmiiflora ‘Emily McKenzie,’ bears orange, maroon-splotched blooms on 30-inch stems and is one of the hardiest (USDA zone 6) of the large-flowered crocosmias.
Crocosmia x crocosmiiflora ‘George Davison,’ an heirloom dating from 1902, has small lemon-colored flowers on 2-foot stems.
Crocosmia x crocosmiiflora ‘Mistral’, a chance seedling of C. masonorum, has geranium-red flowers on 3- to 4-foot stems in July and August and is hardy to USDA zones 5 or 6.
Crocosmia x crocosmiiflora ‘Solfatare,’ one of the oldest surviving French varieties, has unusual bronze leaves perfectly set off by apricot-yellow flowers that open in August. Choose blue-flowered companions such as agapanthus or Salvia guaranitica for this crocosmia, which grows to a height of 2 to 3 feet.
Photos of many of the cultivars mentioned may be accessed by visiting www.crocosmia.nl/regularvarieties.html, the website of Kwekerij Davelaar, crocosmia specialists.
Selected from: Article by WSU Clark County Extension
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