Lettuce "Rouge Grenobloise"

* Growing lettuce in protected and open ground.
In greenhouses, head varieties are grown by seedlings in two periods: winter-spring (2 rotations) and autumn (1-2 rotations).
In northern latitudes (Estonia), autumn culture with planting seedlings (3-4 leaves) is justified. Optimal sowing August 3-10, planting seedlings in the first ten days of September. For winter sowing (from December 5), supplementary lighting is needed. Without lighting, it can be grown from late January (harvest in late February - March).
Seedlings are grown in pots or peat blocks. Before germination +18..+20°C, after germination +8..+12°C during the day and +6..+10°C at night. Prick out in the cotyledon phase.
Nutrition: nitrogen - 60-80, phosphorus - 8-10, potassium - 80-100, magnesium - 20-30 mg/l. Before planting, the soil is abundantly moistened.
Planting density: large varieties ("Batavia") - 30x30...25 cm, medium - 25x25 cm. In spring less frequent (16-20 pcs/m²), in autumn denser (25-30 pcs/m²).
Watering and climate: watering in the morning with active ventilation afterwards. At the beginning of head formation, the temperature is lowered: +14+18°C during the day and +8+12°C at night (so that the head is dense).

In open ground, different sowing dates are used. The earliest production is obtained by winter sowing (late October - early November).
The soil should be loose (light loam or sandy loam). Sowing in furrows 1-1.5 cm deep. Acidic soils are limed.
Seedling method for open ground: sowing 30-35 days before planting. Prick out in the true leaf phase. Planted according to the scheme appropriate for the variety.
Care: loosening, weeding, watering (during head formation - only along the furrows).
Harvesting: in the evening or early morning when the plants are cooled.