HOW TO HYBRIDISE CLEMATIS

New hybrid clematis have been appearing for the last one hundred years. Original hybrids are of course the result of a cross-fertilisation between two species. Species are plants that are found growing wild and which reproduce themselves true from seed. Hybrids never produce true

seedlings and must therefore be perpetuated by cuttings, grafts or layers. Nowadays most large-flowering hybrids are the result of the cross-fertilising of two large-flowering hybrids. The idea being to get the best out of both plants, for example when we first raised our new variety Elsie Frost we crossed the varieties Mrs. Cholmondeley and Lasurstern, obtaining the shape of Lasurstern with the colour of Mrs. Cholmondeley. The early-flowering varieties, Patens and Lanuginosa varieties, will produce seedheads readily without any help from us and often, if sown, will produce a new variety, although they will produce a very large majority of inferior varieties which have to be thrown away. To produce a new variety using two selected varieties one should wait until the bud of one of them is just about to open, then with a pair of sharp scissors carefully remove all the petals (or sepals as they are really called). The anthers which produce the pollen must also be removed and this is done by cutting through the stamens, leaving just the central stigma on the end of the pistil. To prevent any pollen getting on to the stigma, the whole bud, or what is left of it, should be enclosed in a polythene or muslin bag. Within a few days the stigma will be in a viscid receptive state ready for the transfer of pollen from the plant we have selected. To find out if it is ready, remove the polythene bag to inspect the stigma. If it is shiny and covered with a sticky fluid, then everthing is ready. This fluid traps the pollen and transmits it down the pistil to the ovary, where fertilisation takes place and seeds are formed. When all is ready, choose a sunny day if possible and bring the chosen flower, which should be full out, and gently shake the pollen from the anthers on to the stigma. Or one can cut the stamens off the chosen plant and shake the anthers over the stigma, or the pollen can be transferred by a soft camel-hair brush, making sure that the stigma is well covered with pollen. If a cross is required from plants of two different flowering seasons, then the pollen of the first variety of flower, say in the spring, can be kept in an airtight container in a very dry place until the flower of the second variety comes out later in the summer. When the operation is complete, cover the stigma again with a polythene bag for a few days to make sure that no stray pollen is transferred. If one is not sure that the operation has been successful it can always be repeated in two or three days time. Leave the polythene bag on for a week or two until you are sure that the fertilisation has taken place and there is no risk of a stray pollination, it can then be removed to enable the sun and air to ripen the seed which usually takes about four months. It can either be sown immediately and stood outside to winter, bringing the seed pan in in the spring. Or it can be stored in a dry box or cupboard during the winter, sowing in the spring in either a greenhouse or frame.

Do not expect anything to come up immediately, or in a few weeks’ time. Clematis seed will often remain dormant for a year or two! So if you are an impatient gardener give up the idea of raising new clematis. Even when a new seedling appears it takes another two years before the plant will flower! So it is a very long job, the whole operation taking three of four years before we can see the results of our efforts! Not too long to wait, however, if the results are as good as some of those which have appeared in the last twenty years. Once the new variety has flowered and you are sure that it is worth growing it can be kept true by means of cuttings, layers or grafts. You can then give it a name, perhaps even naming the plant after yourself, or a near relative. Nurserymen are always keen to get new varieties and if your plant is good enough they will introduce it for you to the general public by listing it in their catalogues. You will then have the thrill of seeing your name listed among all the other clematis and if it is very good you will have the gratifying pleasure of knowing that your name will go down to posterity.

There are endless possibilities in the hybridising of clematis, most of the colours in the clematis world are in the pastel shades and if we could simply intensify these colours it would be a great step forward. Do we want a scarlet clematis or a bright yellow one, I wonder? Most people would say no, but a clematis to rival the Bougainvillea would really be something. Varieties that are wilt-resisting would be a major breakthrough and varieties that are bushier in habit would also be a great attraction to the bungalow owner. The future I am sure will hold many exciting changes in the clematis world. They have only recently celebrated their first century, and so compared with roses, clematis are newcomers.

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