In the seasonal rush to plant spring-flowering bulbs, ” takes a certain amount of courage and a steady gaze. If all this isn’t enough to keep you from seeking them out, the whole family has been reclassified. They’ve been ostracized by the Liliaceae family (lilies et al.) and now band together as Colchicaceae. There’s more: they’re not really bulbs, but corms (technically a swollen underground stem), and they produce big, strappy leaves in spring that are hard to camouflage.
Now that you know the worst, let’s get on with why these autumn gems deserve a place in our gardens. Quite simply, it’s because they’re so beautiful. The goblet-shaped flowers bloom in shades of lilac, pink or white, and stand five to eight inches (13 to 18 cm) tall and two to three inches (5 to 8 cm) wide. Planted singly or in generous drifts, they make an impact in the garden at a time when many plants are past their prime. Tucked under green-leaved spring-flowering shrubs, such as forsythias and rhododendrons, they offer a splash of fall colour to the drab branches. Colchicums also make ideal container plants — pop them into a pot of fading summer annuals and they’ll bloom a few weeks later, providing a fresh fall look. When they’ve finished blooming, plant them in the garden, where they’ll flower for years.
Because colchicums bloom “naked” — without their leaves — it’s best to combine them with leafy groundcovers, such as earlier-flowering cranesbills (Geranium spp. and cvs.), so the fall flowers rise up through the foliage, making the perennials appear to rebloom. Other effective partners include dark-leaved plants that show off colchicums’ pastel flowers, such as ‘Obsidian’ heuchera and black mondo grass.
Planting the corms among groundcovers also helps disguise the tall, fairly wide, hosta-like leaves that appear in the springtime. As frustrating as it may be, resist the impulse to cut down the foliage; it collects the energy needed to produce those lovely fall flowers.
How to grow colchicums
When to plant: late summer to early fall for blooms the same year. Corms must be fresh and not dried out.
How deep: about four inches (10 cm); a little deeper in sandy soil and shallower in rich organic soil.
Soil: well drained
Exposure: part shade, but plants will tolerate full sun if well watered.
Moisture: they prefer dry summers, so don’t irrigate during this dormant period.
Division: divide only if overcrowded; separate corms in early summer after foliage has ripened and plants are dormant.
Hardiness: Zone 4; in areas with scant snow cover, protect with evergreen boughs over winter.
Colchicum ‘Autumn Queen’ lilac petals with silvery, checkered pattern
C. ‘Lilac Wonder’ amethyst blooms
C. ‘The Giant’ white-throated violet flowers
C. ‘Waterlily’ double, lavender-pink flowers
C. autumnale ‘Album’ single white flowers
Crocus or colchicum?
Colchicums are erroneously referred to as autumn crocuses, but they differ in many ways. True crocuses have three stamens, while colchicums have six. Crocus leaves are narrow with a central white stripe, but colchicums have wide, solid green leaves. The shoots of crocus emerge from the top of the corms; those of colchicums sprout off-centre. Beware that all parts of colchicums are toxic if ingested and may cause skin irritation. (That makes them pest-resistant, too.) Like colchicums, autumn crocuses are readily available and can be planted in late summer or early fall for blooms the same season. Although their flowers are more diminutive than those of colchicums, they make an impact when planted in groups or drifts.