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Poor pollination is a common problem on many perennial trees, vines, and bushes. Pollination and fruit set can widely vary from year to year. Poor pollination can also be the consequence as the plants grow older.


Every spring, bud swell is followed by flowering. The plant may have a shorter flowering period than a longer flowering period depending upon the climate, the age of the plant, and the root health of the plant. The weaker plant will also have a more prolonged flowering period in any given year. A stronger plant will normally have a shorter flowering period in any given year.
The climate can largely determine the strength of pollination for each flower. The ideal temperature is 75%F. As temperatures become lower or as temperatures become higher, pollination becomes weaker during the greater temperature variations during the period of pollination. Normally, cooler temperatures in the spring are the greatest cause of poor pollination.
The hormone which normally dicates the power of pollination is auxin. The auxin is a hormone which is produced in the upper part of the plant. Its production is greater when the temperatures is approximately 75%F.
When the flowering season begins, the ethylene level in a plant greatly increases. The ethylene is a hormone that tends to reduce the movement of auxing from the upper part of the plant to the lower part of the plant. Therefore, at the beginning of flowering the ethylene level in a plant raises in order to keep more of the auxin in the upper part of the plant where flowering is occurring.
During cold temperatures, the plant has a difficult time synthesizing auxin and the level of ethylene does not rise high enough in order to keep the auxin in the upper part of the plant where the flowering is occurring.
If it rains during a flowering season, this auxin may be washed out of the flowers, thus creating an auxin deficient flower. During rainy periods, pollination of flowers becomes much weaker.
The first flowers on the plant will normally have sufficient auxin for stronger pollination. As the flowers become lighter, the amount of auxin supplied to these flowers becomes less and less.
If the flowers lack auxin, fertilization will become difficult. The strength of the male part to fertilize the female part and the chance for the female part to accept the fertilization depends upon the amount of auxin that is contained in this flower.
It is very important to have honey bees during the period of pollination. They will gather nectar from the strong flowers and their body parts will absorb some of the auxin that is in the strong flower. They will then fly to the weak flower to gather nectar and transfer some of this auxin to the weaker flowers, so that they have more auxin for stronger pollination. Many years, however, there are insufficient honey bees to provide adequate pollination. This is particularly true during rainy weather or colder weather. Therefore, pollination will be weaker.


It is very simple to supply adequate auxin to each flower. The application of 3 pints of Flower Power to the plant during the period of when there is approximately 10% appearance of flowers on the plant. This should supply sufficient auxin for both the flowers that are present and the developing buds which will become flowers. The application of Flower Power will guarantee that there should be sufficient auxin so that during periods of temperature extremes, there should be enough auxin in the flower for stronger pollination.
The application of Flower Power in order to increase the power of pollination needs only to be done one time. If there is a weak plant or plants with a prolonged period of flowering, a second application may need to be done 10 days after the first application.

J/JHS Articles/PEP – Weak Flower Pollination 030107bc