Hybridising Tuberous Begonias

The Story Of The Begonia by Dr A C Blair

Hybridisation By John Hamilton

The whole process begins in April, this is when the basal cuttings are rooted. These cuttings are used to provide the female flowers to be used for hybridising later in the year. The stem cuttings rooted in subsequent months are used to provide the male (pollen) flowers. The reason for using cuttings is that due to the efforts of previous hybridists, the stamens prominent on the original single flowered species plants have been changed into petals, giving us the double flowered varieties with the form we know today. To overcome this and obtain pollen the plants need to be starved and very poorly grown, in this way they will fling single flowers. It is however not really a good idea to neglect your plants sufficiently enough to do this, more especially if you have just forked out £20 for them. The alternative is to root a cutting and let the first flowers develop. I have read that the cuttings should be potted into a very poor compost, but I have found that a normal compost will produce perfectly acceptable results.

All the cuttings are housed in the greenhouse for the beginning of September and the heating is put on. This I have found to be essential if pollen flowers are ready to be used, you will actually be able to see the pollen on the petals. It is then a matter of transferring the pollen to the female flowers, these are easily recognisable by the seed pods positioned behind the flowers. Not every female is of use and those with a very long stigma should be ignored (the stigma is the central part of the female flower into which the pollen is transferred). The pollen once attached to the stigma needs to grow to reach the seed pod, if the stigma is too long this makes this operation difficult and pollination is very poor. To transfer the pollen a soft brush is needed, I use a kiddies paintbrush with black hairs, so the pollen can be seen. To obtain the pollen gently tap the stamens (the central part of the male flower) and the pollen will fall onto the petals (the paint brush can be used too with a gently brush motion). The brush can then be used to pick up the sticky pollen and transfer it to the female flower. When pollinating, all three parts of the stigma must have pollen transferred to them, or only part of the seed pod will ripen. The whole operation is best carried out on a sunny day, preferably around midday when the pollen count is at its highest.

If the cross has taken, the petals of the female flower will normally fall off within a week, do not despair however if this is not the case as not all varieties do so. The whole ripening process takes about seven weeks, if the pod is shed after three to four weeks or before, the cross has not taken. When the pod begins to go brown and the outside of it turns papery, is should be removed. After two or three days in a warm place it will split and the seed can be removed and cleaned. Cleaning the seed is a simple process. Using two sheets of white paper, the seed is put on one sheet, it is then rolled, by tilting the paper and gently tapping from one sheet to the other. The viable seed will roll, whilst the chaff remains behind. Repeat the process three or four times, then transfer to an envelope, marking on it the cross. The final stage of the process is to store in a cool dry place until it is to be sown.

Recommended varieties for hybridisation:-

Tahiti, Midas, Jenny Barclay, First Love, Zoe Colledge, Linda Jackson, Fred Martin, Dorothy White, Falstaff.