Examine the watercress to find stalks with roots. If you buy watercress at the grocery store, place it in water for three days, which encourages the stalks to form roots.
Fill a large pot or bucket with compost. The pot or bucket has to have drainage holes on the bottom. Leave the soil 3 to 4 inches below the pot's rim.
Firm the compost with your hands.
Water the compost until it's well-saturated. The water should run out of the drainage holes. Allow the container or bucket to sit for an hour or until the water stops coming out of the drainage holes.
Insert a dibble into the compost to make a hole. Keep the holes 2 inches from the pot's rim, and allow at least 4 inches of space between each hole.
Place the rooted end of the watercress into the hole. Firm the soil around the stem with your fingers.
Water the watercress again. Watercress needs ample moisture to grow, so water the plants every day to keep the compost damp.
Insert the pot or bucket into a larger container to hold any water that comes out the drainage holes. Do not allow the water to become stagnant. Empty the water from the container once a week.
Locate a cool, shady area to grow the watercress. In about a month, the watercress will be established and growing.
Feed the watercress after it begins producing new shoots. Mix and apply an all-purpose fertilizer according to label directions.