Watercress is one of the most valuable salad vegetables from the point of view of vitamins. May be grown without running water by digging a trench 2 ft. wide and 1 ft. deep, in a sunny position, placing 6 in. of rotten manure in the bottom, covering with 3 in. of soil and sowing seed thinly in April and again in August, or planting cuttings. The trench should be flooded with water fairly frequently while the plants are in growth. Permanent beds are usually made of concrete and are about 4 ft. wide and 6-10 in. in depth. The flow of water should be controlled by suitable sluices or valves. Three inches of good soil should be placed in the bottom of the bed and a little clean gravel or sand on top. Cuttings from selected plants are dibbled into this bed 6 in. apart each way. Usually two plantings are made, one in May or June and the other in October. Restrict water to a depth of 11 in. at first, but increase slowly according to the growth of the plants. Three to four inches is sufficient under ordinary conditions.
The principal disease of watercress is mildew.