Watercress is perennial plant with hollow stems and small heart-shaped leaves. It has a peppery flavor that's sharp but not bitter. As the name suggests, watercress is a water-loving plant, and it typically is found growing near creeks and ponds. Popular varieties include English Watercress and Broad Leaf Cress.
Watercress grows best in cool but sunny spots. If there is a small creek or stream on your property, grow watercress there. Otherwise, it may be necessary to create a bog. Dig a hole about 2' across and 12" deep (Image 1). Loosely fit black plastic pond liner over the hole, pressing it down with your hands. Trim the excess off the top, leaving a 3" or 4" lip at the top. Use a garden fork to punch a few holes in the sides of the liner for drainage (Image 2).
Combine one part garden soil, one part coarse builder's sand, one part compost, and one part mushroom compost. Add a handful of slow-release fertilizer to the mix. Pour the mixture into the bog, filling it to within 1" or 2" of the top. Cover the remaining exposed liner with soil. Fill the bog thoroughly with water.
Thin seedlings to about 5" to 8" apart after germination. Maintain adequate moisture levels in the bog. In hot weather, watercress will be covered with small white flowers. When cool weather returns, cut back the flowers to encourage new tender growth.
To harvest watercress, cut the leaves and stems a few inches above the ground. Watercress is a perennial, meaning it will come back year after year, and new growth will come up from the ground after each cutting. Although it can be harvested any time of year, its flavor is best during the cooler months.