Detailed Guide to Hand-Pollination Techniques for Watermelon

I. Selection of Node Position

For watermelons grown under protected cultivation, the fruit-setting node position can be lower; for open-field cultivation in spring, the fruit-setting node position should be higher; for early-maturing varieties, the fruit-setting node position is low; for late-maturing varieties, the fruit-setting node position should be higher. The suitable fruit-bearing node position depends on the variety and climatic conditions. Generally, early-maturing varieties set fruit at nodes 12-15 on the main vine. Mid- to late-maturing varieties set fruit at nodes 20-25 on the main vine, generally the 2nd or 3rd female flower. Under conditions of low temperature, insufficient fertilizer, weak light, or poor plant vigor, fruit setting can be appropriately delayed.

II. Selection of Female Flowers

Female flowers at the fruit-setting node with a large ovary, abundant fine hairs, and a long, thick fruit stalk set fruit easily, and the fruit is large with high yield. Conversely, female flowers with small petals, a small and round ovary, a short and thin flower stalk, and sparse fine hairs do not set fruit easily; even if fruit sets, the fruit is small, of poor quality, and low yield.

III. Selection of Male Flowers

Male flowers used for pollination should be selected from those that open on the same day, have bright colors, and have a relatively large corolla diameter.

IV. Pollination Time

1. Pollination Time

Under sunny conditions, the corolla begins to loosen at around 5 a.m., the anthers begin to split and release pollen at around 6 a.m., and the corolla fully opens. By 12 noon, the corolla color fades and begins to close. From 8-10 a.m. is when the female flower stigma and male flower pollen are most physiologically active, and it is also the best time for hand pollination.

2. Completion Time

The completion time for hand pollination of watermelon is preferably 7 days, with a maximum of no more than 10 days. If pollination completion exceeds 10 days, fruit setting will be uneven, fruit sizes will be irregular, the harvest period will not be concentrated, and yield will also decrease by 10%-15%.

V. Pollination Techniques

1. Flower-to-Flower Method

When pollinating, gently lift the female flower stalk to expose the stigma, then select a male flower that opens on the same day, pick it together with its stalk, turn the petals outward to expose the stamens, and gently smear the pollen onto the stigma of the female flower at the fruit-setting node, so that the pollen is evenly distributed on the stigma. One male flower can pollinate 2-4 female flowers.

2. Brush Dipping Method

Pick male flowers that open on the same day, collect the pollen into a clean container and mix it, dip a soft brush or small brush into the pollen, aim at the stigma of the female flower, and gently smear a few times until the stigma has obvious yellow pollen.

VI. Precautions

If there is a lot of rainy weather during the watermelon flowering period, affecting normal pollination, you can put paper caps or small plastic bags on the female and male flowers 1 day in advance before the rain to protect them from rain. Remove the bags when pollinating, and after pollination put the cap back on the female flower for protection, then remove it after 3 days. If there is a shower during flowering and pollination, pollinate 2 hours after the rain. Pollination should be completed within 3 hours. If there is no rain within 3 hours after pollination, normal management can proceed; if there is light rain within 3 hours, pollinate once more.

After pollination, hang paper tags of different colors at the pollinated fruit node as markers. This confirms that pollination has been done, prevents repeated pollination, and also makes it easy to determine the watermelon's maturity period so that it can be harvested at the right time.

VII. Pollination Inspection

On the afternoon of the day after pollination, if the female flower's fruit stalk bends and grows downward, and the front end of the ovary begins to touch the ground, it indicates successful pollination. If the female flower's fruit stalk still points upward or still extends forward, it indicates that pollination did not take. At this time, clear the marker tag on that plant and reselect a female flower for pollination.