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Plants in the rain garden will be more susceptible to stress when they are young. You will need to water the rain garden plants regularly until they are established. This usually takes one or two growing seasons. After the plants are established, you should not have to water them except during prolonged dry periods.
If your rain garden has been in place for a while, you may need to divide some of the plants. Dividing plants can help thin out the garden. If the plants have spread out so that there is no new growth in the center, dividing will help the plant have less of a "leggy" look and will make it more dense. When you divide your plants, you can give sectins of the plant away to friends or neighbors, or you can plant pieces in other areas of your yard -- or in a new rain garden! Click here for step by step instructions for dividing plants.
While the plants in the rain garden are young and becoming established, they may need to be watered during dry periods so that they will develop good, deep roots. Be sure to water the garden thoroughly. Simulate a rain event by filling the garden with about an inch of water every couple of weeks during long dry periods. This will help the water soak deeply into the ground. If you water with a sprinkler, set some containers around the garden. When the containers fill with about an inch of water, your garden has received a good watering.
Weeding and Pruning
Pulling weeds is important to reduce competition in the garden for space, light and water. Most weeds are pioneer species, which means they grow very quickly and will fill open spaces, crowding out the desirable plants. Remove only those plants you are certain are weeds. Weeds will become less prevalent in the garden over time as the native wildflowers, grasses and sedges you've planted begin to mature and out-compete the weeds. Rain garden plants may be pruned or thinned to maintain a more manicured look. Here are pictures of some common weeds that you may find in your rain garden:
Dead vegetation and debris should be removed formt he garden from time to time. Vegetation should be cut back in the early spring. Keeping seedheads on during the witner will add visual interest to the winter landscape and will provide food for songbirds and cover for wildlife. In spring, cut back all tattered plants and dead stalks before new growth begins. If the plants are very dense, you may want to use a weed whacker to mow the plantings back to a height of about 6 inches.
Mulching will help protect plants as they become established and reduces weed growth. Each spring the rain garden should be mulched with 3 inches of double shredded hardwood mulch. Chipped bark is leass desirable as it tends to float when the garden fills with water. Some plants are dormant until late spring, so be careful when mulching not to bury the plant crown. The need to mulch each year will diminish over time as the plants mature and fill the exposed soil surfaces.