When hybridising or cross-fertilising tulip bulbs, hybridisers must first decide on the right ‘parents’ for the new flower. That requires extensive knowledge of the existing selection and the various features of those tulips. These may include color, growth rate, disease resistance, flower shape, bud presentation, bulb growth and bulb quality.
Additionally, now that hybridisation is mechanised and no longer done by hand, new bulbs have to be much stronger than in the past.
Once the right bulbs have been chosen, the work can begin. The bulbs go into the ground in October. The following spring, the hybridiser removes the stamens as soon as the flowers open. The pollen is then stored and dried carefully.
When the mother plant blooms, it is dusted with pollen from the father plant. The hybridiser waits until the stigma (the very top of the pistil) is ripe and slightly damp. Using a small brush or cotton swab, the pollen is brushed onto the pistil. Temperature and humidity are of the essence here, and both must be just right. If and when the pollination is successful, fertilisation will take place within a few days in the mother plant’s ovary. Hybridisers must now watch over the plant like mother hens, so that all the plant’s energy can be devoted to growing seeds.
The seeds germinate in July and seed pods can be harvested. The pods are dried to prevent fungus from occurring. Healthy seeds are then separated from dead ones. The hybridiser must ensure that only the best seeds are used for the breeding process.
In January, the selected seeds are planted in fine potting soil and kept in a cooled space to simulate a mild winter. In their natural environment, tulips grow in a climate that includes a winter. Every year, they need a cool or cold period to bloom well.
The seeds sprout in early spring. At first, they resemble grass shoots. Growing in the ground beneath the shoot is a tiny bulb, no larger than a pea. The fastest-growing bulbs are harvested in July and only the largest are planted the following autumn.
This selection process can take another two or three years. After four or five years, the bulb is large enough to produce its own flower.
Once the tulip bulb is able to produce flowers, the positive selection process begins. The most beautiful and most promising types are selected from the seeds of many tulips. These are labelled with a code, which breeders call the ‘seedling number’. The year of hybridisation, the parents, and the selection number are often recorded in code on this label.
From the moment of the first positive selection, all the features of that bulb type are carefully assessed. Numerous selections over the next few years will eventually filter out many types, because they are either not strong enough or have characteristics not suited to the weather conditions or other factors. This is called negative selection.
After years of assessment and selection, the best breeds are reduced to a number of bulbs that are fit for the market. This is also the moment at which a tulip is given a name.
There is a continuing need for new breeds, because fashions change, and so does customer demand. Tulip types can also age, which makes them unmarketable. New sorts of tulips therefore replace the old, and completely new crosses between shapes and colors are also created.
