Technology of transplanting seedlings and grafting methods for cucumber onto pumpkin

Quality of transplants directly determines the future harvest of vegetable crops. To obtain robust plants with a well-developed root system, seedlings are pricked out immediately after the emergence of the first true leaves. Timely transfer to individual containers prevents the plants from becoming leggy and provides them with the necessary feeding area.

Pricking out seedlings and cucumber grafting technology

When pricking out, seedlings are carefully removed from the trays using a dibber, holding them by the cotyledonous leaves and maintaining the root ball. Long roots can be pinched — this procedure stimulates the branching of the root system and does not harm the plant. Once transplanted into nutrient-rich substrate, the seedlings are firmly pressed with soil and watered immediately using a fine-rosed watering can.

A few days before planting in a permanent location, the transplants are top-dressed with liquid fertilizer. The quality of emergence is also affected by correct sowing: seeds should be distributed evenly and not too densely. If seedlings fail to emerge, the causes may be infection on the seeds (causing pre-emergence damping-off), pathogens in the soil, excessive irrigation, or sowing too deep. Soil that is too dense hinders germination, while in an excessively loose substrate, the seed coat does not fall off and remains on the seedling.

To improve the endurance and yield of cucumber cultivars, grafting onto pumpkin is used. Wild related species possess powerful immunity to diseases and high vitality. The stems are fused using the approach grafting method.

1. Sow pumpkin seeds in pots one week later than cucumbers.
2. Make oblique tongue-shaped cuts on stems of equal thickness up to the middle of the stem: on the cucumber — from bottom to top, on the pumpkin — from top to bottom.
3. Insert the stems into each other with the tongues and tie the junction tightly with wool thread.
4. Seal the junction hermetically with film to exclude air access to the wound.
5. Place the grafted plants in conditions of high humidity and heat, and after 2 weeks, cut off the cucumber root and the pumpkin top.

Biological features of cucumber and temperature regime

The cucumber is a moisture-loving annual vine with a branching stem. The main shoot grows to more than 3 meters and is capable of forming adventitious roots. The root system of the cucumber is superficial: the taproot goes to a depth of up to 60–70 cm (in sandy soils), while the bulk of absorbing lateral roots is concentrated in the top soil layer up to 25 cm. Because of this, the plant is extremely demanding regarding air humidity and soil moisture.

• Optimal soil moisture — 75–85 %
• Optimal air humidity — 80–85 %
• Depth of lateral roots — up to 25 cm
• Minimum germination temperature — 18 °C
• Optimal germination temperature — 25–28 °C

Soil temperature directly determines the speed of emergence. This allows for an accurate calculation of when the transplants are ready for planting in a greenhouse or open soil. Below are the timings for seed germination of cucumber depending on the temperature regime.

For normal growth and development of plants during the growing season, a temperature in the range of 18–26 °C is required. If it is too cold in the greenhouse, bush development slows down, flower buds drop, and fruit set does not occur. Extreme temperature values lead to the rapid death of the plantings.

Cucumber yield depends on the ratio of male and female flowers. Female flowers are primarily set on side shoots of the first, second, and third orders. To stimulate their mass appearance, agronomists use special technological techniques.

Increasing the number of female flowers on a cucumber is facilitated by the following measures:

• sparse planting of plants with an interval of 35–40 cm in a row;
• moderate drying out of the soil;
• temporary controlled temperature reduction;
• pre-sowing seed warming;
• increasing the concentration of carbon dioxide in the ground layer of air;
• pinching the growing bud on the 3rd–4th leaf;
• precise cutting of the shoot top during pruning of the bushes.

Cucumber agrotechnics: from seed preparation to harvesting

Cucumber yield depends directly on the age of the seeds and their storage conditions. Seeds retain viability for 8 years or more, but their vitality decreases over time. The best results are shown by regionalized seeds stored for 2–3 years, which were kept in a warm and dry place. Using fresh seeds from the previous year's harvest or seeds after cold storage leads to the formation of long vines with an abundance of barren flowers.

To accelerate fruiting in open ground by two weeks, the crop is grown using the transplant method. Planting is carried out at the age of 2–3 weeks, when seedlings have formed 2–3 true leaves. With the direct sowing method, it is critical to wait for the soil to warm up: for normal seed germination, its temperature must be above 14 °C.

• Soil temperature for emergence — above 14 °C
• Age of transplants for planting — 2–3 true leaves
• Temperature for fertilization — 18–24 °C
• Irrigation frequency — every 2–3 days
• Harvesting frequency — 2–3 times a week

Flowering of early-maturing cultivars begins 30–40 days after emergence, and 50–60 days for late-maturing ones. The cucumber forms unisexual flowers that require cross-pollination by insects. Optimal fertilization occurs at a temperature of 18–24 °C. In cold and rainy weather, insect flight ceases, fruit set drops, and partial fertilization of ovules leads to the formation of deformed fruits. In greenhouse operations, this problem is solved by growing parthenocarpic hybrids, which form long, seedless fruits without pollination.

To maintain high productivity of plantings, it is necessary to strictly observe the rules for irrigation and harvesting. A lack of moisture or the use of unsuitable water quickly leads to the shedding of fruit set. When caring for the crop, follow these rules:

• Water the plants every 2–3 days.
• Do not use cold water or water with high chlorine content for irrigation.
• Ensure access for bees to the plantings for high-quality pollination (with the exception of parthenocarpic hybrids).
• Carry out harvesting of young fruits at least 2–3 times a week.

Regular harvesting stimulates the formation of new fruit set. Large overripe fruits consume too many nutrients, which slows down the development of the remaining fruit set and reduces the overall productivity of the bush.