When to Prune a Dwarf Rhododendron

Identifying Dwarf Rhododendrons

• Although you'll find no straightforward definition of what makes a rhododendron dwarf, one that grows less than 3 feet in 10 years can safely be considered a dwarf variety. Cultivars such as “Mary Fleming” (Rhododendron “Mary Fleming”) with pale yellow flowers grow to heights of between 1.5 and 2.5 feet, for instance. It is winter hardy in U.S. Department of Agriculture plant hardiness zones 5 through 8. “Girard Dwarf Lavender” (Rhododendron “Girard Dwarf Lavender”), which usually tops out at 3 feet in height and spread, is another compact rhododendron and is hardy in USDA zones 4 through 7. While dwarf rhododendrons may sometimes be classified as azaleas, they are really all members of the Rhododendron species.

Shaping

• Because dwarf rhododendrons flower on old wood, prune after they bloom, the timing of which varies but is usually in spring. As soon as flowers are spent, you may thin out branches or prune off their ends in order to create a more pleasing, rounded shape. Even smaller varieties can be trained to look like little trees if you prune to a small trunk and a thinner canopy. Prune to a whorl of leaves instead of clipping randomly along a branch; this will ensure natural-looking new growth. Remove diseased branches any time.

Deadheading

• Deadheading is the removal of spent flower clusters, which is important for many reasons. For one thing, most rhododendrons flower thickly, so when the bloom finishes they are left covered with unattractive withered blossoms. For another, deadheading prevents the plant from setting seed, which would compromise its ability to form nice blooms for next year. Carefully snap or clip off the flower clusters below the stems, watching out for the formation of new buds so as not to remove them.

Disbudding

• Disbudding isn’t necessary unless your rhododendron needs thickening. If it has thin branches, you can pinch off terminal buds to encourage it to form side branches, which will make the plant fuller. Dwarf rhododendrons benefit from this if they are leggy, and you can also disbud taller rhododendrons to train them to a more compact, dwarflike form. When using clippers for any pruning task, disinfect them before and afterward with rubbing alcohol to prevent spread of disease.