Rhododendrons, azaleas worth the extra effort
It won't be long until landscapes are colored with the magnificent blooms of rhododendrons and azaleas. If you are like most people, you are probably wondering about the difference between the two plants.
All azaleas are rhododendrons, but not all rhododendrons are azaleas. Azaleas are members of the genus Rhododendron. Azaleas can be evergreen, but many lose their leaves in the fall; rhododendrons are evergreen. Rhododendrons have large, leathery foliage; the leaves of azaleas are smaller. The flowers of azaleas are usually tubular; a rhododendron's flowers are shaped like bells.
The most widely-grown rhododendron in our area is P.J.M. It is very cold hardy and more tolerant of our soils than other varieties. It grows up to 5 feet tall and about as wide. It boasts bright lavender-pink flowers in spring.
Girard hybrids are evergreen azaleas with bright green leaves. Hot Shot shows off scarlet flowers, while the flowers of Renee Michelle are clear pink.
The Northern Lights series are particularly floriferous. The flowers of Northern Hi-Lights are creamy white with a bright yellow upper petal. Mandarin Lights brightens the garden with brilliant orange blooms.
Both azaleas and rhododendrons are acid-loving plants. In order for them to flourish in our alkaline soils, proper planting is essential, including site selection and soil preparation. Choose a spot with morning sun and afternoon shade or filtered light all day.
Amend the soil with an abundance of organic matter - peat moss, mushroom compost, leaf mold or decomposed pine bark - to meet rhododendron's need for well-drained soil. If your soil is heavy clay, consider creating a raised bed.
Add soil sulfur to the area before planting and fertilize with an acid-based fertilizer formulated for rhododendrons. Always follow the directions on the label - more is not better. Continue to fertilize every year in early spring when flower buds swell to maintain the acidity of the soil.
When their soil is not acidic enough, rhododendrons may develop chlorosis, a yellowing of leaves while the veins remain dark green.
Rhododendrons and azaleas purchased growing in containers are easy to plant. Begin by removing the plant from its pot and gently loosening and pulling roots outward. Dig a nice wide hole just deep enough so the plant sits at the same or above the level of the surrounding soil. Never plant rhododendrons too deep - it may cause their death.
Mulch rhododendrons with a 2- to 3-inch layer of organic mulch to keep their roots cool and the soil moist.
After flowering, remove spent flowers by bending them carefully until they snap from their stems. Work carefully; next year's flower buds are just under old flowers.
Remove any invading weeds by hand pulling to avoid disturbing shallow roots. Water rhododendrons during periods of drought; they cannot tolerate dry spells. An inch of water per week is recommended.
Protection from winter sun and cold, drying winds is also necessary. In areas where rhododendrons may be exposed to severe winter conditions, they should be wrapped in burlap.
Give rhododendrons and azaleas the additional attention they require and be rewarded with spectacular spring blooms, attractive green foliage in summer and winter interest provided by their branching or mahogany-tinted evergreen leaves.
• Diana Stoll is a horticulturist and the garden center manager at The Planter's Palette, 28W571 Roosevelt Road, Winfield. Call (630) 293-1040, ext. 2, or visit planterspalette.com.