Detailed Explanation of the Latest Scientific Cultivation Techniques for Winter Melon

I. Timely Sowing

Winter melon likes warmth and tolerates heat. To obtain a high yield, suitable climatic conditions for fruit setting and fruit development should be chosen for planting. Climatic conditions have the greatest influence on the fruit-setting rate of winter melon, so special attention should be paid to seasonal arrangement. Sunny weather, higher temperatures, and greater humidity are favorable for fruit setting; dry air, low temperatures, and rainy days are not favorable for the development of winter melon fruit. Therefore, special attention must be paid at sowing time to avoid, as much as possible, having the planted winter melon bloom and set fruit during this period. According to many years of planting experience, in the Beijing area the planting period for spring greenhouse winter melon is chosen in mid-March, which is relatively favorable for winter melon production. After planting, this winter melon has a growth period of 100——120 days, and the seedling-raising period is about 40 days. The sowing dates of the rootstock and scion are determined according to the planting date. Because the scion germinates more slowly than the rootstock, the scion should be sown first and the rootstock afterward. The scion is sown 3-5 days earlier than the rootstock. Generally, the scion is sown in late January and the rootstock in early February. In this way, winter melon fruit setting and fruit development occur around May, when temperature and sunshine are relatively suitable.

II. Preparation of Seedling Pots

Both scion seedlings and rootstocks can be raised in seedling pots. The nutrient soil in the pots must use fertile garden soil that has not grown cucurbits in recent years; sandy soil is best. For each cubic meter of nutrient soil, add 1 kg of compound fertilizer and 0.3 cubic meters of decomposed organic fertilizer. After thorough mixing, put it into nutrient pots with a diameter of about 10 cm. After filling, water the pots thoroughly and place them in a warm shed for later use. The preparation of seedling pots is generally carried out 3-4 days before sowing.

III. Seed Soaking and Germination

In order to increase the germination rate of seeds and speed up seed germination, both winter melon seeds and rootstock seeds need to be soaked and germinated. For winter melon, select seeds with a white, glossy seed coat, which have high germinating power. The seed coat of winter melon seeds is relatively thick, hindering water absorption and oxygen penetration, so its seeds germinate with much more difficulty than ordinary seeds. The method of soaking and germinating is: first soak the selected seeds in hot water at 50°C-60°C, stirring constantly until the water temperature drops to about 30°C, then stop stirring and continue soaking for 12—14 hours so that the seeds fully absorb water. Wrap them with gauze or a towel, place them in a warm place, and germinate best under a constant temperature of 25°C. After 3-4 days, when most seeds have sprouted white shoots, they can be sown. For the rootstock, select plump pumpkin seeds, soak them in warm water at about 30 degrees for 6-8 hours, then place them under a constant temperature of 25°C for germination. After 1-2 days, most seeds will sprout white shoots and can be sown. For planting this small winter melon, generally 250 grams of winter melon seeds and 700 grams of pumpkin seeds are needed per mu. After planting, 3000—3200 grafted seedlings are needed per mu; in production, seedlings can be raised at 3500 plants per mu.

IV. Sowing

The entire sowing process is completed in a warm shed. During this period, the temperature around Beijing is relatively low, and the warm shed needs appropriate heating by adding fire to keep the temperature inside the shed at about 30°C. The day before sowing the scion, water the nutrient soil in the pots thoroughly, use a wooden stick or finger to press a small hole 1-2 cm deep in the middle of the pot, select winter melon seeds that have already germinated, place one seed flat in each pot, with the sprout slightly tilted downward, which is best. Then gently sprinkle sieved fine sandy soil on the surface of the nutrient pot to cover the seeds. After sowing, sprinkle an appropriate amount of water on the pots. The method of sowing the rootstock is basically the same as that of sowing the scion, except that the sowing date is several days later.

V. Seedling Management After Sowing

After sowing and before emergence, pay attention to watering, but do not use too much water to prevent seed rot and root rot; just keep the soil moist. Before the scion emerges, keep the temperature inside the shed at 30°C—35°C during the day and about 16°C--20°C at night. In the morning, evening, and at night, add straw curtains outside the warm shed. After about a week, the seedlings can emerge. After emergence, lower the temperature in time, to 25-28°C during the day and about 15°C at night. The rootstock grows quickly and does not require high temperatures; the rootstock requires a temperature 3-5°C lower than the scion. In management, attention should be paid to preventing excessive seedling growth and avoiding the formation of leggy seedlings. After emergence, ventilation can be appropriately carried out during the day. By controlling the opening time of the straw curtains in the morning and evening, appropriately extend the lighting time and improve photosynthetic efficiency. When the rootstock grows 1-2 true leaves and the calendar seedling age is about 20 days, while the scion has just grown 1-2 true leaves and the seedling age is about 23 days, grafting can begin.

VI. Grafting

Grafting must also be carried out in a warm shed. During grafting, the temperature in the shed should be kept above 25°C and the relative air humidity above 90%. Grafting operations must be carried out under shade. Generally, straw curtains are added outside the shed at the grafting operation position, which can reduce the stimulation of sunlight on the graft wound. The tools used for grafting are relatively simple: this kind of thin blade and special small plastic clips for grafting. The commonly used grafting method is called the splice grafting method, which has the advantages of simple operation, fast grafting speed, and high survival rate. Before grafting, first water all the rootstock nutrient pots and scion nutrient pots thoroughly at once. Gently pull out several scions from the lower part, place them in a bowl, soak the roots in water, and then grafting can begin. The specific operation method is: first pick up a pot of rootstock, pinch the two leaves with two fingers of one hand, hold the blade with the other hand, and cut diagonally upward near the lower part of the other cotyledon, thus cutting out a 45-degree angled surface in front of and above the cotyledon. When cutting, cut down in one stroke; the cut surface should be smooth, and the cut surface should be 0.6-0.8 cm long. Then take a prepared scion, similarly pinch the leaf with one hand, hold the blade with the other hand, and cut upward at a 45-degree angle 1.5--2 cm below the cotyledon. Place the cut scion against the rootstock and secure it with a grafting clip. It can be seen that the cut surface of the scion basically matches the cut surface of the rootstock. Complete all grafting tasks in the same way. After grafting, the seedling pots should be placed neatly to one side. In time, use bamboo strips to prop up a small arch shed above the pots, then cover it with plastic film, and also cover the outside of the film with shading cloth. In this way, it can provide wind protection, light avoidance, and warmth.

VII. Management After Grafting

After grafting, the seedling pots should remain in the arch shed. Within three days, do not let in wind or light. During the day, the indoor temperature should be kept above 25°C, and at night above 15°C. On cloudy and snowy days, maintain the shed temperature by measures such as increasing the frequency of adding coal, so as to accelerate wound healing.

After three days, ventilate appropriately in the morning and evening, gradually increasing the time from ten minutes to half an hour. When the light is not too strong in the morning and evening, after ventilation, remove the shading cloth to let in some light, increasing from half an hour to two hours. After seven days, the small arch shed can be removed. Twelve days after grafting, the grafted seedlings enter the normal management stage. At this time, the daytime temperature should be between 25-30°C, and at night about 15°C. One week before planting, harden the seedlings at low temperature, with a daytime temperature of 20°C and a nighttime temperature of about 10°C. Twenty days after grafting, when the grafted seedlings have grown 2-3 true leaves, they can be planted.

VIII. Planting

In the Beijing area, the planting period for spring greenhouse winter melon is in mid-March. Ten days before planting, prepare the land and make beds in the greenhouse. Before this, sufficient base fertilizer had already been applied in the field, using fermented dry chicken manure at 2000---2500 kg per mu, and ternary compound fertilizer at 50 kg per mu. After turning and leveling, make small high beds 1.3 meters wide, with a bed height of 15-20 cm. Planting should be chosen on a sunny morning. Select seedlings with thick stems and nodes and thick, dark leaves for planting. Use a shovel to dig planting holes on both sides of the bed, with two holes about 33 cm apart, and sprinkle an appropriate amount of white lime powder, which can disinfect and sterilize the soil. In this way, each bed can plant two rows of winter melon seedlings. When planting, remove the plastic nutrient pot, place the seedling together with the nutrient soil into the planting hole, and then cover the area around the seedling with soil. After all planting in one greenhouse is completed, immediately water with planting water. The planting water should be watered thoroughly at one time.

IX. Management After Planting

In mid-to-late March, the temperature is relatively low. After planting, first focus on heat preservation to promote seedling recovery. For the first one or two days, close the greenhouse tightly to raise the temperature inside the shed. The temperature inside the shed should be kept at 30-35°C. When the temperature reaches above 35°C, ventilate appropriately. After 2-3 days, seedling recovery is basically complete. After 4-5 days, the seedlings begin to grow. After one week, cracks begin to appear on the ground, and some small grass seedlings also grow. At this time, cultivate and weed in time. The cultivation depth should be 3-5 cm, with the principle of not loosening the roots of the seedlings. On one hand, remove the small weeds on the surface; on the other hand, cover the cracks on the ground with soft soil, which can preserve moisture. At this time, some seedlings also grow branches at the lower part. When loosening the soil, remove these small branches and keep only the main stem, which can reduce nutrient consumption. Three to four days after cultivation, set up the trellis. The trellis is set up near the winter melon vines to prepare for hanging the vines. The specific method is: take bamboo poles about two meters long and insert them evenly near the seedlings, then place bamboo poles horizontally on top, and tie the bamboo poles together in this way (za), so the trellis is very sturdy, and in the future the winter melon vines can grow along the bamboo trellis. After this, the melon seedlings enter the vine-extending stage. The stem vines grow faster, and the plants lodge because they cannot bear overly heavy leaves, changing from upright growth to creeping growth, so this is called the vine-extending stage. During this period, the growth characteristics of the plants are: leaf area expands, new leaves and side vines differentiate, some begin to show flower buds, and growth gradually becomes vigorous. Appropriate small amounts of water are needed, but do not allow waterlogging, so as to avoid soil water accumulation causing root hypoxia in the plants.

Vine Tying

About 30 days after planting, the vines can be tied to the trellis, that is, tying the longer plants to the trellis, also called vine hanging. The specific method is: first sort out the plants, because during this period the plants have grown many side branches, that is, these forks, as well as these tendrils, and male and female flowers. The female flowers and male flowers of winter melon have obvious differences. The female flower has an ovary below it, with shapes including long oval, short oval, and flat round. After fruit setting, the ovary develops into a winter melon. The male flower has no ovary below it and cannot develop into a winter melon. Generally, only 2-3 female flower buds are kept on one seedling; all excess buds are removed. Remove all forks and keep only one main stem. Also remove tendrils like these. The purpose of doing this is to concentrate nutrients for cultivating the fruit.

Then use grass ties to tie the melon vines to the trellis, taking care not to damage the stems. After vine tying, the melon vines have better ventilation and air permeability, which is beneficial to plant growth. It is also possible to stretch an iron wire above the bed, tie a sturdy plastic rope to the middle-lower part of the melon vine, and tie the other end to the iron wire above. The melon vine will also grow upward along the plastic rope, with the same effect as the previous trellis.

Fruit Setting

Because winter melon is grown in a greenhouse, there are no insects in the shed for pollination, and it cannot rely on air flow for pollination, which easily leads to fewer fruits and slow growth. In order to help winter melon set fruit, artificial auxiliary measures are generally used, that is, using 0.1% thidiazuron wettable powder to dip flowers; it is a plant growth regulator.

Specific Operation Method

Carry this out 1-2 days before flowering, when the flower buds have not yet opened. According to the product instructions, dilute thidiazuron wettable powder into a 100-fold aqueous solution. Use a spray bottle to spray the solution onto the surface of the flower buds and ovaries, spraying all around. The flower buds can also be dipped into the aqueous solution. In this way, the fruit-setting rate of winter melon can reach more than 90%. Using this growth regulator can also accelerate fruit expansion, increase yield, and advance maturity. This growth regulator does not replace flower pollination, but directly causes the winter melon ovary to develop into a winter melon. Therefore, the winter melon produced by this method cannot be used as seed for the next generation. Water, fertilizer, and temperature management during the fruit-setting period: grafted seedlings grow quickly, have well-developed root systems, and strong stress resistance, and tend to grow vines easily. To avoid vigorous vines and small fruits, do not water during the fruit-setting period. Control the daytime temperature between 25-30°C, and at night it must not be lower than 15°C.