How to Prune & Care for a Rhododendron

Overview

Rhododendrons require some pruning and care to maintain health and vigor. The broadleaf evergreen shrub grows in USDA hardiness zones 4 through 10, depending on the species. Rhododendrons reach anywhere from 3 feet to 15 feet tall with a 4 to 20-foot spread. The shrubs perform best in partial shade. Prolific blooms appear in spring, ranging in hue from white to pink to yellow. Rhododendrons provide year-round color with dark green leaves and bright flowers. The leaves of some varieties, such as P.J.M, turn mahogany in cold winters. Rhododendrons make an eye-catching, easy maintenance choice for almost any landscape.

Prune

Step 1

Identify terminal growth buds. These buds appear slender and longer than flower buds. Pinch off any terminal growth buds on young rhododendrons before seasonal growth begins. Before leaf expansion, pinch back growing shoot tips. This encourages fuller, less leggy growth.

Step 2

Remove spent blooms. Bend the flower stalk until it breaks from the stem. Watch for growth buds located at the base of flower stalks. Avoid damaging those.

Step 3

Prune rhododendrons right after the shrub finishes flowering. Don't wait to prune or you risk damaging bud formation for the next spring. The plant generally needs only light cutting to maintain shape. Remove any dead branches or diseased parts of the shrub as needed.

Care

Step 1

Provide an acidic soil environment. Rhododendrons perform best with a soil pH between 4.5 and 5.5. Test the soil's pH using a test kit. Amend the soil as needed. Opt for a complete, acid fertilizer. Apply the fertilizer after flowering.

Step 2

Give the shrub supplemental water. Rhododendrons have shallow roots and don't tolerate dry spells. Water when rainfall measures less than 1 inch per week. One deep watering a week promotes healthier root growth. Make sure the soil drains well because rhododendrons won't thrive in soggy soils.

Step 3

Spread a 3-inch layer of mulch. The Ohio State University Extension recommends mixing bark mulch with peat moss for rhododendrons. This conserves the soil moisture and slowly amends the soil, while providing air flow and proper drainage. The mulch also protects the shrub from winter injury in cold climates.

Step 4

Check the shrub regularly for disease or insect damage. Damage to leaves--such as yellowing or defoliation--indicates a problem. Rust, root rot, root weevils, aphids and spider mites can plague rhododendrons. Identify any problems early and seek the appropriate treatment.

Things You'll Need

  • Pruners
  • Soil pH test kit
  • Fertilizer
  • Peat moss
  • Mulch

References

  • "Pictorial Guide of landscape Plants"; M. Jane Coleman Helmer, Ph. D.; 1988
  • "The Pruning Book"; Lee Reich, Ph.D.; 2010
  • Ohio State University Extension: Maintaining Healthy Rhododendrons and Azaleas in the Landscape
  • Oregon State University Extension: Azalea and Rhododendron Care and Culture

Who Can Help

  • The American Rhododendron Society
Keywords: rhododendron care, maintain healthy rhododendron, pruning rhododendrons

About this Author

Kitten Arbuckle is a freelance writer living in Indiana. Arbuckle has been writing for websites such as Garden Guides since early 2009. Her education includes training in landscaping, certification in herbal medicine from a botanical sanctuary and a variety of college courses.