The plants are very frost-sensitive and local custom generally avoids a sowing date before the incidence of frosts has passed. The seedlings are thinned out to their final stand when the first true leaves are showing. Care must be taken with crops scheduled for seed production to ensure that only one seedling is left per station, this is especially important for the production of basic seed. The frequency of irrigation will depend on the soil type and climate, but because watermelon plants develop a deep and extensive root system applications can be kept to a minimum; in dry regions, sufficient irrigation should be applied prior to sowing to restore the soil to field capacity.