A Detailed Guide to Walnut Tree Planting Time and Hand Pollination Methods

Walnut is one of the four major nuts. Its tree not only has a certain ornamental value, but is also a good material for construction, furniture and other processing. Walnut trees are planted in many places in our country. In order to increase their fruiting rate, hand pollination is often used. Let's take a look below at when walnut trees are generally planted and what hand pollination methods there are.

1. When are walnut trees generally planted?

Any fruit grower who has planted walnut trees knows that they sprout and grow leaves in spring, bloom in May, and the fruit ripens in October, so planting walnut trees generally should be chosen before spring sprouting or after the fruit ripens in autumn. Spring and autumn are the best periods for planting walnut trees. For example, spring planting should be carried out after the soil thaws and before the saplings sprout, while autumn planting should be done after the Start of Autumn and before the soil freezes.

Walnut trees are not strict about environmental conditions. They can be planted in areas with an annual average temperature between 9 and 16°C, annual rainfall of 500 to 800 mm, and an altitude of 600 to 1200 m. Walnut has a fairly wide adaptability to soil, but because it is a deep-rooted fruit tree and has weak resistance, it is more suitable to choose deep, fertile loam with strong water retention. Walnut is a light-loving fruit tree and requires sufficient sunlight. When building an orchard in mountainous areas, it is best to choose a south-facing slope.

2. What hand pollination methods are there for walnut trees?

Different pollination methods can be used for walnuts under different levels of management and with different varieties.

1. Dusting method

For short precocious walnut saplings, a pollinator can be used for pollination, or a medical laryngeal powder sprayer can be used instead. When pollinating, put the pollen into the glass bottle of the powder sprayer and spray it over the middle and upper part of the crown. Note that the nozzle should be kept more than 30 cm away from the stigma.

2. Spraying method

Mix pollen with granulated sugar and water in a ratio of 1:50:3000, or pollen:boric acid:water in a ratio of 1:0.2:3000, to make a pollen liquid, and spray it evenly onto the crown with a sprayer at 9:00-10:00 or 15:00-16:00. It can also be done together with foliar fertilizer spraying, using a nutrient solution of pollen:sugar:urea:water at 1:50:10:3000. After the stigma withers, spray foliar fertilizer with urea:boric acid:water at a ratio of 0.2:0.3:100 once every about 15 d, for 2 to 3 consecutive sprays, which can promote rapid fruit expansion and growth and enhance fruit quality.

3. Shaking method

Mix pollen and starch in a ratio of 1:10 and stir well, put it into a 2 to 4 layer gauze bag, seal the bag mouth tightly, tie it to a bamboo pole, and shake and scatter it above the crown facing the wind. Under normal climate conditions, assisted hand pollination can increase the fruit-setting rate by 15% to 25%. If there is abnormal weather such as low temperature, rain, strong wind, or frost, or for walnut trees with the habit of blooming twice, assisted hand pollination can increase the fruit-setting rate by 20% to 35%.

4. Hanging method

Pick male inflorescences that are about to shed pollen, make them into bundles of 4 to 5 each, and hang them on the upper part of the crown to let them shed pollen freely.