Technologies for growing cucumbers via transplants and direct sowing

Transplants or direct sowing: how to minimize root stress

Growing cucumbers via transplants allows for harvesting 7–10 days earlier, but involves a high risk of damaging the root system. In all cucurbit crops, root hairs hardly regenerate after damage. During standard transplanting, the plant pauses growth for approximately 10 days, losing all the time advantage gained over direct sowing.

• Time advantage with transplants — 7–10 days
• Age of transplants for planting — 25 days
• Distance between seeds in a cluster — 4 cm
• Depth of trench for biofuel — 1 spade blade
• Cold hardiness of seedlings under cover — down to -5…-6 °C

To reduce stress during transplanting, transplants are grown in individual bottomless containers. Paper cylinders made of several layers of newspaper or plastic cups with both ends cut off and a volume of 300 ml are suitable for this. The optimal age of transplants for planting into the soil is 25 days (the phase of one true leaf) or even earlier, in the cotyledon phase. During this period, the root system is just beginning to form and tolerates transplanting more easily.

When planting, paper cups are placed into the holes entirely, after removing the securing rubber band — soaked paper does not hinder root growth. Plastic containers are carefully slid off, holding the soil ball with your hand. Planting is completed by gently irrigating with warm water and covering the leaves with two layers of lutrasil. To protect against slugs, young plants are covered with cut 5–6 liter plastic bottles, hilling them up with soil on the sides.

Bed preparation, sowing, and temperature regime in the greenhouse

Direct sowing of dry seed in a greenhouse eliminates the labor associated with transplants and yields more hardy plants. Sowing is carried out in early May into pre-warmed soil. Before sowing, the bed is thoroughly watered with hot water; seeds are placed 2–3 per cluster, edge-down into the soil, at a distance of 4 cm from each other. Until emergence, the sown beds are covered with polyethylene film, and topped with two layers of lutrasil.

To create the optimal temperature regime, soil for cucumbers is prepared in advance using biofuel. This method provides the root system with a constant supply of heat and stimulates the growing season. The bed is prepared a week before the planned sowing of seeds.

1. Dig a trench to the depth and width of a spade blade.
2. Add dry hay, leaves, or undecomposed compost to it.
3. Return the excavated soil over the hay, place a board on top, and compact the soil by walking on it.
4. Water the bed abundantly and cover it hermetically with black film to warm up.

A week later, when the hay begins to decompose and release heat, sowing begins. Seedlings emerge after 7 days, after which the polyethylene film is immediately removed to avoid sunburn on the plants. The double lutrasil is left lying directly on the seedlings. Under such a cover, seedlings in a greenhouse can withstand spring frosts down to -5…-6 °C. In the 1–2 true leaves phase, extra seedlings in the clusters are carefully replanted.

Cucumbers require constantly moist, but not waterlogged soil without turning into sludge. It is optimal to use drip irrigation or perforated plastic bottles for supplying water with top dressing (one bottle provides moisture for 4 plants). Since cucumbers grow at night and are sensitive to cooling air in high greenhouses, it is necessary to turn on local heating on cold nights.

Seed preparation and choice of cultivation method

Preparation of seed material is the first step in protecting future crops from dangerous infections. Heating the seeds allows for their complete clearance of pathogens causing anthracnose and bacteriosis. This can be done in advance or immediately before sowing by choosing the most convenient temperature regime.

• Water temperature in a thermos for express heating — 53 °C
• Time for express seed heating — 15–20 minutes
• Duration of heating on a radiator — 1 month
• Service life of cleaned willow hoops — 5–6 years
• Height of the trellis for vertical training — 1.5 m

For regions with cool summers, including the North-West, traditional open-field cultivation is not suitable. Here, the crop is grown under temporary covers, where plants are positioned horizontally. At night, warm air from the soil is retained within the small volume of the low hotbed, protecting the plantings from hypothermia. During the day, the cover is removed, and at night it is stretched over the hoops again.

A frame for such hotbeds can be made independently from metal hoops or ordinary willow twigs. Willow hoops last a long time if the material is prepared and stored correctly. To extend the service life of the harvested materials, it is enough to follow three simple steps.

1. Remove the bark from the cut twigs immediately after harvesting, while it is still easy to peel.
2. Bend the cleaned twigs into hoops and insert the ends into the soil of the bed.
3. In autumn, remove the hoops from the ground, tie them into bundles, and store them under a roof.

Rules for tying and training vines

In tall greenhouses, after the frosts have passed, cucumbers are trained onto vertical trellises. Plants are secured with a loose knot under the first true leaf, and the stem is carefully wound around the twine in a counter-clockwise direction under each leaf. As it grows, the stem continues to be guided by hand, and upon reaching the top wire, it is draped over it and allowed to grow downwards.

The training scheme depends on the chosen cultivation method and the biological characteristics of the hybrid or cultivar. With horizontal cultivation in hotbeds, there is no need to train the vines. In vertical cultivation, the technology of "blinding" the lower tier and pinching side shoots is mandatory.

When using vertical cultivation, 3–4 lower leaves on the main stem are blinded by completely removing all shoots and buds from their axils. This prevents the growth of lower vines, which do not produce fruit due to a lack of light, but actively consume nutrients. Side shoots above the blinded zone are pinched immediately after 2 leaves have formed on them. When the plant is draped over the top wire of the trellis, the pinching of side branches is stopped, allowing them to branch freely and fruit in clusters.

To simplify maintenance, one can use modern single-stem hybrids, which lack side shoots or have them greatly shortened. They do not require training, and their apical growth is limited by a flower or a cluster of flowers. Their harvest is formed only on the main stem, so the individual productivity of such plants is lower. This disadvantage is compensated for by dense planting of up to 10 plants per square meter, maintaining a high total yield per greenhouse area.