How To Buy Bulbs, Corms And Tubers

The main outdoor planting season for bulbs, corms and tubers is in the autumn with bulbs on sale from mid-August to late November.

Lilies have a very long growing season and, if they have had to be transported over great distances, may not arrive in time for the autumn selling season. Buy them as soon as they arrive and plant immediately. If soil conditions are very bad pot them and plant out when conditions are good in the spring, do not store them.

Many corms, though dormant during the winter, are not completely hardy and are liable to be killed in the soil before growth can start in the spring. These are stored in frost-proof conditions and sold from late January to the end of April, for planting as soon as the soil (not the air) is frost-free. If potted up in a frost-free greenhouse they can be had in flower much earlier. Treated in this way they can be planted out as soon as air frosts are unlikely, but must be hardened off first.


There is a small group of plants which flower in autumn, often well before their leaves, the main growth of which is not till spring. They have a short summer dormant season and are sold in July-August.

Heat Treated

Bulbs are sometimes marked ‘prepared’. This means either that they have been heat treated so that they will flower before their normal season, or that they have been cool stored past their normal flowering season so that they flower later. These are available in August-September and should be planted immediately for growing indoors for Christmas flowering.

Greenhouse bulbs

Greenhouse bulbs include those which are available in autumn but make their growth during the winter, e.g. ixias, Gladiolus nana. These can, of course, be planted outside in mild districts, and in any case can be put out by the spring. Holding them dry until the spring is not always a success. They also include those plants which while they can be grown quite successfully outside can be obtained much earlier by growing in a cool house. Varieties of narcissi and tulips which will stand this treatment are often marked as ‘forcing’ varieties.

True greenhouse plants are those which need a higher temperature than is likely to be experienced outdoors, especially during the period September to May. Their planting seasons vary enormously and depend not only on the season of flowering or growth but also on the amount of heat that can be supplied.

How to Select Bulbs, Corms and Tubers in a Shop

Is the shop temperature suitable? If it freezes at night half-hardy bulbs may be damaged and go soft on the outside. If it is too hot (e.g. near the radiator or other source of heat), the bulbs will wither or start to grow shoots prematurely without root growth, and some fungal and bacterial diseases will attack bruised tissues. Tubers liable to wither, such as dahlias, should be prepacked in polythene. See that this is intact. Embryo buds are damaged by withdrawal of water during withering and also by high temperatures. Prepared bulbs lose the effect of the treatment in such conditions. Expensive bulbs should be in shavings, sawdust or peat moss.

Are the bulbs etc. clean? Dirty stock can carry soil-borne diseases and is likely to prevent you looking for bruising and other troubles. Is the stock well housed and properly labelled with variety name and grade as well as price? Narcissus bulbs can be single-nosed, double-nosed or mother bulbs. The more ‘noses’ the more main growths, each with a flower. Is a mother bulb, with three noses going to give you a better display than three single-nosed bulbs-compare the prices. Single-nosed bulbs are best for using with a bulb planter, as they will not stick in the hole, but fall to the bottom. Bulbs for naturalizing should not contain a lot of very small bulbs which will not flower the same year.

Corms are sold by size, the cms denoting the circumference of the corm. Very big corms have fewer advantages than big bulbs, e.g. it is usually better to have one good spike per gladiolus than one and a small one. Exhibition growers choose medium size corms. Large cyclamen corms have fewer years ahead of them and often take longer to settle than small ones.

Hyacinths of medium size give one good spike against one and a small one of the very large bulb. It may pay you to pick off the small one when it starts to emerge to keep the good spike from growing lop-sidedly.

If you can handle the stock before purchasing do so carefully. If a sample of daffodils or irises has some bulbs which are obviously underweight and are soft to the touch leave the lot as it will be impossible to make sure you are not introducing narcissus fly larvae (maggots) or other pest which has eaten out the interior. If when you carefully move a scale leaf or two you find a fungal disease and you are prepared to dip the bulbs in a fungicide before planting, hyacinths may still be all right to buy, but irises with ink disease (black patches) are to be avoided and so are tulips and gladioli with scabby patches (tulip fire and gladiolus scab). Why buy trouble? Show the shopkeeper and he can report to the grower who should not legally be selling diseased stock. Lily bulbs which have the scales falling off probably have basal rot. A similar disease may cause narcissi to have a faulty base plate without a complete ring of roots. Such bulbs spread their diseases to the soil and to other bulbs. They should be burnt.

The only other troubles likely to affect bulbs are not readily seen at this stage. They are best avoided by buying from a reputable source. Virus diseases may cause striped or yellowing foliage or broken colour in the flowers (desired in some tulips). There is no cure for virus diseases. Greenfly eggs may be on the bulb scales of small irises and aphids (i.e. greenflies, blackflies etc.) may attack any bulb in growth; especially susceptible are the fleshy leaves of lachenalias. An aphid spray or (indoors) aerosol should be used as soon as they are seen, as aphids may spread virus diseases.

In the shop it now remains to see that the assistant knows how to handle the stock and does not shovel up corms and tubers with a metal scoop that can remove the buds, and also be sure that each bag is properly labelled.

It is maddening to have to wait until the bulbs flower in the wrong bowls to know that the hyacinth you thought was the blue one is in fact red.

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