How to Grow a Nasturtium Officinale

Location

• Watercress may be cultivated in U.S Department of Agriculture plant hardiness zones 5 to 10, where it prefers full sun or partial shade. It is best grown in a clean, shallow, slowly moving stream. If a stream is not available, watercress may be grown in a bucket with 2 inches of soil and 2 to 3 inches of water. Water should be changed at least once a week. Watercress may also be grown directly in the garden, though it must be watered often to keep soil moist at all times.

Soil

• Watercress is tolerant of a wide range of soil types. If growing in a garden bed, Utah State University recommends adding 4 to 6 inches of well-composted organic matter to a depth of 6 to 8 inches. Container plants should be grown in about 2 inches of composted soil, peat moss, perlite or a good-quality potting mixture. Fertilizer is not generally necessary unless the plant is showing signs of nutrient deficiency. In that case, apply 1 cup of a balanced water soluble fertilizer per 25 square feet.

Propagation

• Watercress is easily propagated from an existing plant. Simply submerge a bunch of watercress stems and leaves from the supermarket in a glass of water until roots appear, then transplant in the garden. Watercress may also be propagated by seed, sprinkled over moist compost and transplanted when they are about 2 inches tall. Watercress is ready for harvest about three weeks after seedlings appear. Just clip the top 6 inches of the stem, along with the leaves. Harvesting watercress is a form of pruning that helps the plant grow bushier.

Considerations

• If growing watercress in a stream, it is important to know that the stream does not drain from fields where animals such as sheep graze. Plants for a Future warns that watercress grown in these conditions may contain live fluke parasites, rendering the plant dangerous if eaten raw. Cooking leaves will destroy parasites, however. Plants grown outside of water generally have a hotter, more peppery flavor, and will require some shade to keep from drying out.