How to Build a Rain Garden

Once the plants are in the ground, cover the inside of the rain garden with a 3-inch layer of mulch to keep the soil moist and to prevent weed seeds from sprouting. Until a rain garden's plants are established, even drought-tolerant plants require supplemental watering to survive dry seasons. Check the mulch depth annually and replenish as necessary. Rain gardens don't require fertilizers beyond the compost used in the soil mix. Weed and prune to keep the rain garden looking its best.