Images: Tim Sandall
Elegant plants from the family Iridaceae can not only be divided to increase stock: removal of excess corms and detaching underground shoots will also bulk up numbers effectively.
Crocosmia and Dierama (right) can be propagated by division in spring. Dig to a depth of 30cm (12in) to avoid damaging the corms and use two garden forks, back to back, to prise the clump apart (left). The roots of both these perennials form ‘chains’ of corms, which can be replanted intact or individually separated off. There is evidence that the younger corms derive some vigour from the older corms so maintaining the ‘chains’ intact may be the better option.
Discard wizened or diseased corms and trim off old leaves to a stump. Replant sections at the same depth in rich, moisture retentive and well-drained soil. Some crocosmias, such as Crocosmia ‘Lucifer’ and C. x crocosmiiflora ‘Jackanapes’, produce underground stems (stolons). These new shoots can be detached, along with fibrous roots, to produce new plants. Dieramas resent disturbance and will take time to flower again after division. Crocosmias flower profusely when crowded so do not divide clumps too often; every two or three years should be enough. A few cultivars of C. x crocosmiifloracan be invasive, so reduction is essential to maintain control.
Fiona Dennis