Choose a cultivar and harvest method
Loose-leaf lettuce or a compact cultivar suited to your conditions is a useful first crop. Read the seed description for mature size, bolting resistance and season. A cultivar for cool outdoor conditions may not suit a warm shelf under a light.
Decide whether to harvest whole plants or individual outer leaves. Whole-plant harvest makes plants of the same age easier to compare. If you pick gradually, record each picking so the total harvest weight is not lost.
Start seeds in a clean plug
Moisten a suitable seedling medium as directed by its manufacturer. Sow at the depth stated on the seed packet and watch moisture. The plug should stay moist without submerging leaves or the base of the stem. After emergence, check lighting and remove persistent condensation.
If several seeds germinate, keep the plant required by your spacing plan and remove extras gently. Avoid pulling them out in a way that damages the remaining roots. Label the cultivar and sowing date: similar-looking rosettes may be different ages.
Transplant when roots can reach moisture
Secure the plug in a pot without pinching the stem. A root or the bottom of the seedling medium must reach moisture in your setup. Roots hanging above water with no moist plug can dry out quickly.
In DWC, start aeration and mark the working level. In Kratky, solution use lowers the level and creates an air gap; do not automatically refill to the lid. Each method needs its own water-level checks.
Care after transplanting
Use a complete fertilizer and a plan for the leafy crop and its stage. Record solution volume, doses and source water. Monitor pH and EC according to that plan; the same EC reading does not guarantee the same nutrient composition.
Check light at the edges and centre of the planting area. As rosettes grow, they can shade neighbours. Move crowded plants apart while keeping pots supported, and monitor temperature around the leaves and in the solution. A constant hot air stream can dry leaf edges.
Check tipburn before adding calcium
Dry edges on young leaves can involve calcium delivery to fast-growing tissue even when calcium is present in the solution. Check climate, dense foliage, airflow and how quickly conditions changed. One damaged edge does not establish that the recipe lacks calcium.
Stretching, bitterness and bolting need a separate review of cultivar, age, light and temperature. Record when signs appear. Raising fertilizer doses without checking EC and roots can add salt stress.
Harvest and plan the next sowing
Harvest with clean tools. For gradual picking, preserve the growing centre and enough healthy leaves. For whole-plant harvest, remove the plant without contaminating edible leaves with solution or growing-medium debris. Keep damaged or suspect leaves out of the harvest.
Judge readiness by cultivar and plant condition; a fixed number of days does not guarantee readiness for harvest. Record fresh weight immediately, plant count and earlier pickings. Clean the system before planting again. For a continuing supply, sow small batches and label their dates.