Rhododendrons (Rhododendron spp.) don't have to hog an entire garden bed. The dwarf “Purple Gem” variety only grows to 2 feet tall, making it an excellent choice for a perennial flower bed or to hide the bare trunks of larger rhododendron varieties. “Purple Gem” grows in U.S. Department of Agriculture plant hardiness zones 4 through 8. The large clusters of violet flowers bloom in midspring, while the evergreen foliage provides year-round color in your landscape.
Grow the “Purple Gem” in well-drained, slightly acidic soil where it can receive partial afternoon shade and bright morning sun. Locations beneath taller trees or shrubs, or along borders, work well for this low-growing rhododendron variety.
Water the rhododendron at least once a week from spring through late summer. Provide 1 to 2 inches of water when the soil begins to feel dry, or enough water to thoroughly moisten the soil to an 8- to 10-inch depth. Reduce watering in fall so the soil almost dries out between each irrigation, allowing the shrub to begin to harden off for winter. Water a final time after the first hard frost, and then resume regular watering in the spring.
Spread 2 inches of mulch over the soil, covering the roots of the rhododendron. Pull the mulch back so it doesn't rest against the trunk of the shrub. Mulch helps retain soil moisture and suppresses weed growth. Replenish the mulch layer each fall.
Apply 1/2 pound of a 6-10-4 fertilizer, or any fertilizer formulated for acid-loving plants, over each 25 square feet of rhododendron bed. Water immediately after application so the fertilizer soaks into the soil. Apply the fertilizer after the “Purple Gem” finishes flowering each year.
Cut off the old flower heads after they begin to wither, with sharp pruning shears. Trim back each flower stem to a leaf or leaf bud. Prune back any overgrown branches and shape the rhododendron lightly, making each cut just above a leaf, to maintain the desired shape and size. Cut out dead or damaged branches to the nearest healthy wood.
Monitor the foliage for yellowed leaves with green veins, which indicates an iron deficiency called chlorosis. Sprinkle 1/8 cup of chelated iron over every 10 square feet of bed in fall and water it into the soil.