Atemoya: Hand Pollination to Increase Fruit Set

If asked to compare the eating quality of various tropical fruits, many of us at ECHO would rank atemoya at or near the top. Our nursery manager, Tim Watkins, described its flavor by saying it “dances on your tongue.” In issue 54 of EDN, the head of our technical department, Dr. Martin Price, described atemoya as one of few “fully adequate” dessert fruits and suggested chilling the fruit in the refrigerator before spooning the creamy, white flesh out of the thin rind.

A few basic atemoya facts from EDN issue 54 include:

• Atemoya is a cross between cherimoya (Annona cherimola) and sugar apple (A. squamosa).
• The flesh of an atemoya fruit is firmer with fewer seeds than sugar apple. Because mature fruits ripen quickly, a good harvesting method for home gardeners is to, twice a day, pick up fruits that have fallen to the ground.
• Atemoya is typically propagated by grafting. However, seeds are a good way to introduce atemoya into a new area; the characteristics of resulting trees will vary but the fruit will probably be good. Seedling trees will start to bear about three years after planting.
• Atemoya thrives under a fairly broad range of conditions in tropical and subtropical climates. Optimal conditions seem to include a dry period of several months during the winter before flowering occurs in the spring. Atemoya will withstand light freezes, but it is intolerant of waterlogged or salty soil.

Have you grown atemoya and experienced limited fruit set? Poor pollination may well be the cause. Atemoya flowers are unattractive to many insects and do not self-pollinate. Furthermore, the female flower parts are quickly desiccated (dried out) by dry weather. Consider hand-pollinating to boost fruit production and quality. Hand pollination increases fruit set by up to 50% in most cases.

Hand pollination of atemoya flowers is a simple procedure based on the interesting fact that the female and male parts (Figure 1) of each flower mature at different times. A flower is functionally female (Figure 2) just before and shortly after the flower petals separate. During this stage, the male flower parts (stamens; Figure 1) are whitish in color. Not more than a day later, the same flower becomes functionally male (Figure 2) as evidenced by wide open petals that easily fall when touched. At the male stage, pollen can be seen on the stamens (Figure 1) which will have turned brown.

To hand pollinate, simply collect pollen from male-stage flowers and brush/dust the pollen onto the stigma (Figure 1) of a flower in the female stage. Male-stage flowers, with their pollen, may be collected and kept in a jar. The pollen grains will readily fall off of the stamens (Figure 1). Transfer the collected pollen to the base (Figure 2) of female-stage flowers using a thin, fine-haired brush; coarse hairs will damage flower parts.

What time of year is hand pollination done? This depends on when flowering occurs. In Florida, flowering begins in March or April. [NOTE: ECHO farm manager, Danny Blank, has observed that a second set of blooms can be induced by a June pruning.] In Australia, atemoya flowers during October and November.

When during the day should pollen be collected and transferred? This depends on when the male and female stages of flower development occur. Here at ECHO, Tim Watkins has successfully hand pollinated atemoya by collecting the pollen late in the afternoon and transferring it to female-stage flowers during the evening or morning. Collected pollen may become nonviable if one waits more than a day to use it. Observe atemoya flower development in your area to decide when to collect and transfer pollen. Also, try using pollen from atemoya (the same tree or other trees and varieties) or sugar apple trees. In Brazil, fruit set increased to a much greater extent with pollen from sugar apple (80% fruit set) than atemoya (21% fruit set). Let us know the results!

We have been collecting atemoya seeds recently, and would be happy to send a free trial packet to those who are serving small scale farmers overseas. We encourage readers in the United States to obtain grafted plants; however, you may send us $4.00 with a request for a packet of seeds.

If you have grown atemoya and had either successes or failures, please let us know. Also tell us something about the climate and location in your area.