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Pollination with female-stage pollen Research has shown that at the start and end of the pollination season trees appear to have a strong tendency to alternate between male and female-stage flowers—male-stage flowers predominating one day, female-stage predominating the next, and so on. This creates problems as pollination requires flowers in the male stage as a pollen source, and flowers in the female stage to pollinate. Male-stage pollen can’t be stored to cover this problem, as its pollinating effectiveness and potency declines rapidly (refrigeration can lengthen the potency time a bit, but not markedly). Study done showing the effect of age of male-stage pollen on fruit set
Studies have shown that to get around this problem you can use pollen from flowers that are removed from the tree in the female stage. Pollen collected from female-stage flowers is not fully developed yet and is stored while it continues to mature off the tree. It was thought to be immature, but has been found to readily grow pollen tubes on the stigmas. This is a fairly new method of pollination that’s still being trialled, but it’s been found that the percentage of fruit set is quite high, and pollen is quite potent after two days. Female-stage pollen can then be stored until female-stage flowers are available to pollinate, which can permit pollination in the morning or early afternoon, before male-stage flowers are ready to collect pollen from. To prepare pollen, collect flowers in the early to mid-female stage. Flowers can be dried after collection for several hours on a mesh screen with a blower, or for 12–24 hours in a purpose-built dryer. This step may or may not be necessary, but it will stop the pollen sticking to the petals and being wasted. Remove the petals, which leaves you with the flower centre containing the stamens and stigmas, and then extract the pollen by rubbing the flower centres between your fingers or on a plastic screen. Flower centres can also be mechanically threshed in a small thresher if you have one. Let the pollen fall through a sieve or a mesh screen onto glass or white paper, then scoop it up and put into a small container with a lid (like a film canister) for use over the following two days. This may seem like a lot of work, but it actually takes less time than wandering around a field looking for male-stage flowers to collect pollen from when there may be very few available. The pollen is stored at room temperature, or can be refrigerated, before being applied to female-stage flowers. Studies show the percentage of fruit set appears highest with 2-day old female-stage pollen, with a higher percentage obtained with pollen collected from unopened flowers than from slightly opened flowers.
For pollinating during periods of alternating male and female-stage flowers, the use of female-stage pollen stored at room temperature is sufficient. Refrigerated female-stage pollen seems to set most fruit at four days, but appears unnecessary and possibly even counterproductive. Female-stage pollen can be useful for labour management in big orchards since it retains viability for several days. Pollination can be done almost all day long (instead of only part-time, which requires hiring part-time workers). This means workers can be hired full-time, and can be doing pollination work all day (be it pollinating or preparing pollen). Next – natural pollination via insects
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