Rhododendrons

Rhododendrons are a very popular and easy plant to grow.  They provide gardens with a very dependable and versatile flowering shrub.

Rhododendrons come in many shapes and sizes; they are a medium to very large shrub with some growing to 5’ while others may reach 20’ or more. Some varieties are rounded and compact while others have a loose growth habit.  They bloom in the spring and early summer and their flowers range in color from pure white through cream and yellow, apricot and salmon, the softest pinks to deep reds, lavender to deep purple and blue. Their foliage also varies in size, shape and shade of green.

Rhododendrons are an incredibly useful shrub.  They can be effectively used in almost any garden and in a variety of ways.  They work very well in woodland setting under tall pines or oaks where there’s dappled sun and the soil is rich in organic matter.  Rhododendrons also provide winter interest as an evergreen and in spring, among the shrub border, they bloom with vibrant flowers. Planted in large massings rhododendrons can have a naturalizing effect in the garden.  They can also be used as specimen plants as well as they have the ability of stand in the garden with their large colorful flowers and dark green foliage.

Oaks and pines are the most commonly mentioned companions for this beautiful shrub. They provide a high canopy of filtered shade while still providing the high degree of light intensity necessary for growth. The mulch provided by oak and pine trees breaks down and provides nutrients. The soil should be kept aerated and the ground moist. For those not having these natural conditions, some additional help may be necessary.

Rhododendrons require only a few conditions in order to thrive; excellent drainage, a soil pH between 4.5 and 6.0, and protection from hot afternoon sun.  Plant the rhododendron out of the wind and in dappled shade, preferably from a high cover of limbs that will give filtered shade all day. Some varieties will take a few hours of direct sun in the morning, but most need protection from the intense afternoon sun.  A certain degree of protection from cold winter wind will reduce the drying winds in winter.  When choosing a site in the garden, a northern exposure is preferable to a southern one.  Also, avoid southern facing slopes as full direct sun is too intense.

Rhododendrons are woodland plants and as such they prefer well-drained soil with high amounts of organic matter. Adding a course textured organic material to poorly drained clay soils will increase drainage ability.  Sandy soil’s on the other hand Have difficulty holding moisture and nutrients and require organic matter which is water retentive.  Add compost and other organic matter through the entire planting area.  This will make it easier for roots to grow beyond the original planting hole.

It’s recommended to plant rhododendron in the spring or fall.  Summer plantings can often stress new planted shrubs.  When planting following these proper planting guidelines. 

After you’ve finished planting, mulch around the shrub or throughout the shrub bed.  Using 2 or 3 inches of pine bark mulch will help reduce weed growth and help the soil retain moisture.  Also, as it breaks down, mulch will add much needed organic matter to the soil. 

As with any shrub, rhododendrons need proper irrigation.  This is especially true of newly planted shrubs.  Since rhododendrons are shallow rooted they may additional irrigation during hot dry weather.  Soaker hoses are generally the preferred method of irrigation as they tend to water deeply without wetting the shrub’s foliage. If you plant your rhododendron in summer, water at least twice each week to provide.  Be mindful that rhododendrons in waterlogged soils will decline and become susceptible to root rot diseases. It is important to reach a balance between regular, deep watering and good drainage to promote a healthy plant.

Rhododendrons need very little pruning. Each spring remove dead wood or any branches which were damaged over the previous winter.  Wait until after they have flowered to prune for aesthetic reasons.  Deadheading rhododendrons is tedious but important. Deadheading is the process of removing spent blooms.  Removing them prevents the rhododendron from putting all its energy toward forming seed heads.  Rather, the energy put forth will go toward the formation next year’s buds.  When deadheading, be careful to remove only the spent flowers and not the forming bud.

Rhododendrons are quite low maintenance once they become established.  Very little fertilization and pruning is required.  In most cases keeping the soil adequately conditioned with organic matter is sufficient to provide the shrubs their nutrients.  Don’t fertilize when planting, again the organic matter should suffice.  Allow newly planted shrubs one to several months, depending on their size, to begin establishing their root system in the landscape soil before applying fertilizer.

A nutrient deficiency can be exhibited by a number of symptoms including stunted growth, smaller than normal leaves, light green to yellowish leaf color and early leaf drop.  In the absence of a soil test and other cultural or pest problems, use a complete fertilizer with a ratio of 3:1:2 or 3:1:3, such as 12-4-8 or 15-5-15.

If fertilization becomes necessary, spring is appropriate since there’s usually adequate moisture to help the shrubs absorb the nutrients.

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