How to Grow Watercress in a Pot

Choose a well-draining potting mix with high levels of organic material. Soilless mixes composed of peat moss, perlite and vermiculite are ideal for container-grown watercress, and a wide variety of formulations are readily available at home and garden centers.

Select a potting mix with a pH suitable for watercress. Although watercress tolerates a wide range of pH values, the best growth occurs in soils between 6.5 and 7.5. Commercial potting mixes formulated for African violets are also suitable for watercress growing.

Place pots containing watercress in a bucket, saucer or other container with at least 2 to 3 inches of water. Use a planting container with drainage holes in the bottom to ensure the potting medium stays wet and roots receive continual exposure to water. When the proper potting mix is used, water from the saucer is drawn up through the drainage holes via capillary action, keeping the soil wet. Watercress plants grow best in soils that are consistently wet.

Water plants frequently, using rainwater, well water or filtered water. The chlorine and fluoride present in most municipal tap water can adversely affect plant growth.

Choose a sunny location for container-grown watercress. Watercress plants require high levels of natural light as well as some protection from wind and frost. Potted plants should not be planted or moved outside until all danger of frost has passed.

Germinate watercress from seeds by sowing ¼ inch deep in evenly wet soil approximately three weeks before the date of the last frost. Seeds will germinate indoors or out, as long as they receive sufficient light, moisture and temperatures from 50 to 60 degrees Fahrenheit.

Apply a balanced water-soluble fertilizer, according to the instructions provided by the manufacturer. Watercress plants are not heavy feeders, but those cultivated in containers benefit from the availability of additional nutrients.

Mulch the soil surface lightly to help conserve moisture and keep containers free of weeds.

Spray insect pests with a solution of soapy water and remove snails by hand. Although watercress plants are generally pest free, they should still be inspected regularly for signs of infestation.