Watercress is a perennial herb that naturally grows in water but will also grow indoors in a container. This herb has a spicy, peppery taste and is used in many dishes like soups and salads. Plant the watercress seeds in the spring and grow them in a sunny location. Never let these water-loving plants dry out. Harvest leaves when needed but, for the best taste, harvest them before the plant flowers.
Fill the container with a soil-free potting medium that is well draining and nutrient rich. Look for media that contains perlite and peat moss.
Water the container from the top to saturate the media and place it on a tray filled with water to keep it wet. Watercress likes plenty of water.
Sow seeds 6.5 mm (1/4 inch) deep. Sow them thickly to ensure you have plenty of sprouts.
Keep the seeds wet until they sprout. Once each sprout has a full set of leaves, thin the plants so they are spaced 20 cm (8 inches) apart.
Place the container in a larger container filled with 7.5 cm (3 inches) of water. This will ensure the watercress stays wet and the roots are submerged. Change the water once a week.
Fertilise the watercress with a liquid 10-10-10 fertiliser at the rate recommended by the manufacturer.
Harvest the dark leaves year round by cutting or pinching off the leaves.