When is the best time to plant watermelons?

The timing of watermelon seedling and sowing is usually affected by protected cultivation facilities and market demand for early listing. Here we mainly discuss how to determine the best sowing time when sowing directly in the open field. Due to differences in natural conditions such as latitude and altitude in watermelon growing areas, as well as the early and late solar terms each year, special attention should be paid to two key factors: ground temperature and late frost when determining the sowing date. So when is the best time to plant watermelons?

When is the best time to plant watermelons?

Watermelon originated in tropical Africa. It is sensitive to temperature and prefers a warm environment. When sowing, you need to ensure that the ground temperature reaches above 10°C so that the seeds can absorb moisture and begin to germinate. If the soil temperature is too low, the seed germination rate will slow down, and if the soil humidity is high, the seeds will easily rot, resulting in lack of seedlings. In addition, after the seedlings emerge from the soil, the temperature should be kept above 15°C to promote the growth of the seedlings and avoid damage from late frost.

Based on these principles, the open-field sowing and harvesting times in China's major watermelon producing areas are roughly as follows:

In the Northeast region, such as Heilongjiang, the suitable sowing period is mid-to-late May, and the harvest period is expected to start from mid-to-late August.

In Liaoning Province, the sowing period is from late April to early May, and the harvesting period starts in late July.

In North China, including Shandong, Hebei, Henan and other provinces, the sowing period is mid-to-late April, and the harvesting period starts from early to mid-July.

In the northwest region, the sowing period is usually from late April to early May, and the harvesting period begins in early to mid-August.

In East China, the sowing period is in early to mid-April, and the harvesting period starts in early to mid-July.

In South China, the spring sowing period is from mid to late February, and the harvesting period is from late May to early June; the autumn sowing period is from late July to early August, and the harvesting period is from late October to early November.

In terms of protected cultivation facilities, watermelon cultivation in greenhouses and small arch sheds has developed rapidly in North China due to the frequent sunny days, sufficient sunshine, and abundant light and heat resources in winter and spring. Plastic greenhouse cultivation usually starts with hotbed seedling cultivation in February, transplanting in March, and harvesting the first batch of commercial melons in May. For cultivation in small plastic greenhouses, seedlings are raised in early March, transplanted in early April, and the first batch of commercial melons is harvested in early to mid-June.

How to grow watermelon

Land preparation and application of base fertilizer: First, deep plow the land and dry it for about half a month, then apply 50 to 75 kg of quicklime per mu. Next, the soil was broken up and leveled into 2.5-meter-wide beds with a height of 40 centimeters on one side and a 20-centimeter slope on the other. Dig a 25 cm deep and 40 cm wide planting ditch on one side of the high ridge, and apply 1,000 to 1,500 kg of decomposed farmyard manure, 25 kg of triple compound fertilizer , 1.5 to 2 kg of borax and 4 kg of magnesium sulfate into the ditch, ensuring that the fertilizer is fully mixed with the backfill soil.

Selecting superior varieties: Selecting superior varieties is the key to achieving high yield and quality. A reasonable combination of early-maturing, mid-maturing and late-maturing varieties can extend the market supply period of watermelon and thus improve economic benefits.

Seed treatment: Before sowing, dry the seeds for 1 to 2 days to enhance physiological activity. Then soak the seeds in warm water at about 55°C for 5 to 6 hours. After pouring out the water, wash the surface of the seeds with 5% lime water, gently rub until it is no longer greasy, rinse with clean water and dry, ready for germination.

Germination method: Germination can be carried out using greenhouse, electric blanket, bedding or body temperature. For large-scale planting, it is recommended to use a greenhouse or electric heating blanket to germinate, or to do it at the same time as corn and rice. For beginners, you can use body temperature or bedding to warm the seeds for germination. Body temperature germination is to place the treated seeds on a wet towel, wrap them with film or plastic bags, and put them in underwear for 24 hours, and they will usually germinate. The bedding heating method for germination is to mix the processed seeds with moist sawdust or fine soil, put them in a paper box, and then put them into an unsealed plastic bag. Place it next to the bedding and use a high-temperature glass bottle filled with boiling water to maintain the temperature. Change the water every 4 to 5 hours. After 36 hours, the seeds will begin to germinate. Regardless of the method used, sowing can be done when the sprouts are about a meter long.

Sowing: Place the germinated seeds flat in the nutrient cup with the buds facing down (because the buds are the roots), put only one seed in each nutrient cup, cover with 1 cm thick nutrient soil, and spray a small amount of 1000 times thiophanate-methyl water (or other fungicides ). Insert the bamboo blocks, cover with film, and secure all around with fine mud. Insert another layer of bamboo blocks, about 15 cm apart from the first layer, cover with another layer of film and secure with fine mud. The temperature in the greenhouse should be maintained at 22 to 28 degrees Celsius, and gradually drop after the first true leaf grows. It should drop by 1 to 2 degrees Celsius every day in the first few days before emergence, and finally reach the same temperature as the natural temperature.

Fertilizer and water management: Watermelon needs to be watered at least 2 to 3 times during its growth period. After the vine extension period, the water requirement increases due to the increase in leaves and longer sunshine hours, so a "vine extension water" should be applied. When the young melons grow to the size of a fist, water them once to ensure yield and quality. After that, decide whether to water based on the climate and soil moisture, and stop watering one week before harvest. When applying top dressing, you should apply fertilizer for promoting seedling growth with caution, apply fertilizer for extending vines skillfully, and focus on applying fertilizer for swelling melons. Top dressing should mainly be quick-acting fertilizer. If there is sufficient base fertilizer, seedling-promoting fertilizer is usually not applied in non-sandy soil. Mainly two top dressing operations are carried out. The vine-stretching fertilizer is mainly nitrogen fertilizer, supplemented with potassium fertilizer to promote nutritional growth. Before the fruit expansion period, apply quick-acting fertilizers, mainly potassium and nitrogen fertilizers. Water and fertilizer management should be reasonably controlled according to local conditions and the growth of melon vines.

Pruning and vine pressing: Watermelon is usually pruned using the double or triple vine pruning method. Double vine pruning is to retain the main vine while selecting a strong side vine and removing all other side vines. Pressing down the vines can fix the melon vines, prevent them from being blown over by the wind, and control their growth. When the main vine grows to about 30 cm, press it down to force it to grow in the specified direction. There are two ways to press the vines: open pressing and hidden pressing. Open pressing is to fix the vines with soil or branches, while hidden pressing is to bury the vines underground. Press the main vine for the first time when it is 40 to 50 cm long, and then press every 4 to 6 nodes, for a total of 2 to 3 times.

Artificial pollination: To ensure that the female flowers bear fruit at the appropriate nodes, artificial pollination must be carried out. Usually the third female flower on the main vine or the second female flower on the side vine is selected, as the fruits at these positions have the best quality and the highest yield. Pollination is carried out between 7 and 10 a.m. every day, using pollen from male flowers that have opened that day to smear the stigma of female flowers. When the young fruits grow to the size of steamed buns, select fruits with good node positions and correct fruit shapes, and leave one fruit on each plant.

Harvest in time: Based on the maturity characteristics of the variety, calculate the number of days after pollination to determine maturity. Characteristics of a ripe watermelon include clear patterns on the surface , a shiny surface, a shrunken navel and stem, burnt tendrils and sparse pubic hairs, and a dull sound when tapped. The harvesting standards are determined based on the transportation distance. Those sold locally can be harvested when they are 90% to 100% ripe, while those shipped from other places can be harvested when they are 80% to 90% ripe.

The above is an introduction to the time and methods of planting watermelons. The environmental conditions for planting watermelons must be met, otherwise it will be difficult to grow high-yield, high-quality watermelons.