‘Bulbs’ come in a true multitude of forms

I can never resist the opportunity to plant a few more bulbs in autumn with spring displays in mind.

Saturday, 6th April 2019, 5:13 pm
Alliums are good value. Picture by Tom Pattinson.

The thought of a succession of colour from January aconites to February snowdrops, and a cacophony of others in March, drives the planting. And what better way to greet spring than have swathes of golden daffodils (narcissi), with multi-coloured tulips to follow?

Much pleasure derives from these early displays because they appear just as the end of short, dark winter days and far from hospitable weather is in sight. But this is only part of the contribution that bulbs can make.

The second bulb-planting activity of a 12-month cycle is with us now, and the garden centres are overflowing with bulbous perennials which, planted in April, will bloom through summer into autumn.

The word ‘bulb’ covers a multitude of perennial plants with swollen storage organs. Corms, rhizomes, tubers, tuberous roots and pseudobulbs all come under that heading.

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True bulbs comprise layers of modified leaves in the form of scales, held together by a basal plate, with an embryo flower surrounded by the main shoot at the centre. Narcissus, muscari and tulip are examples of true spring bulbs; lilium, allium and nerine are summer flowering.

Pseudobulbs operate above the soil or compost and are found on orchids. They come in a variety of shapes and are the source of both leaves and flowering stalks.

Corms have no layers of scales. The main body is a swollen food storage organ with a central shoot. This lasts for a year, shrinking as the plant grows. By the end of a growing season at least one new corm has formed above the original, which has reduced to a thin base-plate. Acidanthera, crocus, freesia and gladiolus are examples.

Rhizomes are thickened food-storage stems that grow horizontally just below soil-level or on the surface. Growth buds appear along the top and sides, forming roots. Propagation is a matter of removing sections with a bud and roots. Agapanthus, canna and convallaria arise from rhizomes.

Tubers are swollen stems below ground and out of sight. Shoots can appear from any part, for example eyes on a potato. Some shrink, but most grow; reference the Cyclamen hederifolium I planted over a decade ago. This winter it had to be moved. The tuber completely covered a large spade blade.

Tuberous roots on dahlia, alstroemeria and clivia are roots, rather than swollen stems or modified leaves, and have terminal buds. Apart from taking stem cuttings, if the roots form a cluster, it’s possible to remove one with a bud to grow on.