- Start by covering the flowers to keep pollinating insects away from them. Wrap them in a paper bag or a piece of cheesecloth, landscaping fabric or fairly loosely woven gauze as soon as they form, but before they open. Fasten the wrap around the peduncle or seal it with adhesive tape or a clip of some kind. Choose male and female flowers from different plants.
- After 12 to 16 hours, or once the flowers have attained sexual maturity, you can pollinate them by hand. Do this early in the morning, just after the dew has formed, on a sunny day. The petals of female flowers are a brighter yellow, and you will see pollen in the male flowers. It is best to remove the petals from a male flower to expose the stamens.
- Hold the female flower open and gently rub its pistil against the stamens. Then blow on the pistil to make sure the pollen is stuck to it.
- Wrap the fertilized flower back up until it fades and the fruit begins to form. You can identify the fruit with a coloured ribbon. It is a good idea to use two or three male flowers for each female flower and to pollinate several flowers in case one or more does not produce any fruit.
Fertilize the flowers in this way as soon as possible in the season, to give the fruit time to ripen.
Based on an article by Nathalie Leuenberger in Quatre-Temps magazine, Vol. 23, No.4