Plant profile: colchicum
Author and bulb enthusiast Rod Leeds selects the best autumn-flowering colchicums
Large-flowered colchicums flower without their leaves throughout autumn, offering an injection of colour. The flowers vary in colour from white to pale pink and dark purple and can be narrow and slim to large and sturdy goblets on sturdy stems. There are multi-petalled selections in white and purple. In the late 19th century, plant collectors introduced the largef lowered species – Colchicum speciosum, Colchicum giganteum, Colchicum bivonae and the variety Colchicum speciosum var. bornmuelleri – into European gardens. One bulb grower in particular, JJ Kerbert of Zocher & Co based in the Dutch city of Haarlem, deliberately crossed these species, producing cultivars that are still grown today. Kerbert often used Colchicum bivonae, which can be tender as a garden plant, to introduce tessellation into the coloured part of the petal. The cultivar Colchicum ‘Autumn Queen’, a fine early f lowering, well-marked cultivar, is now well over 100 years old.
Today there are about 70 named cultivars and 35 autumn-flowering species. Many of the species are difficult to grows. There are also spring-flowering, mostly species colchicums. There have been some extraordinary surprises in the way some colchicums have been introduced into cultivation. One of the first of these was in 1588 when the Flemish botanist Carolus Clusius received corms of Colchicum byzantinum while living in Vienna. The corms had been sent from Constantinople, modern-day Istanbul, to two Viennese ladies who passed on offsets to Clusius. Since no one has since found the source of Colchicum byzantinum in Turkey, all modern stock is a result of those few original corms. The plant is still very vigorous but has now become infertile.
The origins of the must-grow Colchicum speciosum ‘Album’, are equally fascinating. This appeared just over 100 years ago, as a chance seedling in one of the seed beds of the famous Backhouse Nursery of York. From that one corm all current stock has been produced, and all by natural division. Amazingly no other albino selection of Colchicum speciosum has been found. The Backhouse nursery also selected Colchicum speciosum ‘Atrorubens’, which like Colchicum speciosum ‘Album’, holds an Award of Garden Merit from the Royal Horticultural Society.
During the 20th century the great gardener and author EA Bowles championed the genus in his book A Handbook of Crocus and Colchicum for Gardeners published in 1924 with a revised edition in 1952. Bowles was a stickler for correct nomenclature and often bemoaned the fact that colchicums were so inaccurately named. The underlying challenge for botanists is the seasonal difference of f lowers in autumn and leaves in spring. The leaf is often just as important as the flower in defining a particular species or cultivar. A thread of historic cultivars was continued after Bowles’s death by the late nurserywoman Elizabeth Parker-Jervis. Her father had been a great friend of Bowles and as a young woman Elizabeth had visited Bowles at his Enfield home, Myddelton House. In the latter years of the 20th century, she and her husband Johnny ran P-J Nursery near Oxford, specialising in colchicums and it is through Elizabeth that much material perpetuated.
Between 2014 and 2017, the RHS undertook a trial of autumn-flowering colchicums at RHS Garden Hyde Hall in Essex. The trial included many Dutch selections plus additions from private and botanical gardens, where a few growers had preserved stocks from 20th-century collections.
The interest in colchicums has been taken up by a number of European growers with new plants now coming on the market. Many come from the Netherlands but many more, such as Colchicum ‘Faberge’s Silver’ and Colchicum ‘World Champion’s Cup’, are from Lithuania.
• Author Rod Leeds is a writer and expert in autumn-flowering bulbs. His recommendations of the best colchicums for autumn interest can be found over the next five pages.
Cultivation
Colchicums are best planted from June until August when they are dormant. When planting, the top of the dry, brown tunic should be just above soil level. Colchicums thrive in heavy soils and even do well on sandy loams. To keep them growing well it’s a good idea to lift and split the group every three to four years.
They generally suffer from few diseases but in damp summer weather they can be damaged by the keeled slug, a small slug that lives between the corm and the tunic. This only becomes a problem if the emerging bud is eaten. The whole plant is toxic to humans and animals. In fact when writing about the dangers of the plants in his Herbal of 1597, the English botanist John Gerard described meadow saffrons, some of which are still classed as colchicums, as Colchicum strangulatorium.
Viable seed is occasionally set in a number of cultivars.
It is useful in selecting new forms, but uncollected seed can germinate near the parent plant leading to a hybrid group.
The answer is to lift the whole group when in flower and ruthlessly keep only the true flowers.
The smaller-flowered colchicums, such as C. agrippinum and C. autumnale ‘Nancy Lindsay’, are very good companions for the species and cultivars of the winter-green Polypodium ferns as these have fresh fronds in late summer, which fade away in late spring. The dark-flowered colchicum cultivars, such as
C. ‘Benton End’, C. ‘EA Bowles’ and C. speciosum ‘Rubrum’ can be associated with any cultivar of Pulmonaria, even better if the Pulmonaria has been clipped back in July, so both plants look pristine in autumn. If left in situ for many years the colchicum tunics form layers rather like a Russian doll and inhibit the size of the new corm. The white flowers of C. speciosum ‘Album’ can look amazing planted among Ophiopogon planiscapus ‘Kokuryu’. The nearly black leaves of this tough little mondo grass frame the white goblets to perfection.
In grass, the large-flowered colchicums are in their element. In traditional orchards or wildflower meadows they flower well and are supported by the surrounding grass. This does mean that you will need to leave the grass uncut from the end of August until late June. Although, in some years the grass could be cut in November to December and do no damage.
A peculiar characteristic of colchicums is when cut for indoor display they do not need water, and will last well in their dry state in a vase and adding water does not extend their life; you can even grow the corm indoors on a windowsill, without any compost or pot and it will still flower.