Singing Trees Gardens Presents

Six Steps to Success with Rhododendrons & Azaleas


The right plant in the right place! This is the essential first step in a happy relationship with your new rhododendron. Rhododendrons range in size from less than 12 inches to almost 10 feet in height (measured after 10 years of growth). They can be pruned or moved later, but it’s definitely easier to select the appropriate plant in the first place. So plant the low-growing ones where suitable…under windows for example…and the large ones were they will have room to grow. If you are not sure which rhododendron best fi ts your location, just ask. I’m sure we can find one that is just right for you.

EXPOSURE: Rhododendrons on the coast generally do well with direct sun, still it’s best to avoid areas with hot reflective sun, like a southwest exposure against a house. As a general rule, most of the smaller leaf types prefer full sun. The larger leaf types will thrive in “bright shade” areas with little or no direct sun. But remember, all rhododendrons need a good “light level” if they are to bloom well. Areas with only ferns and moss, i.e. redwood forest, are too dark! WIND: Protect your rhododendrons from strong winds, especially salt winds off the ocean. If you live on the bluff, tuck your rhododendrons around on the leeward side of the house, behind a fence or in the shelter of a windbreak planting. Low growing varieties are generally the best choice – they are down out of the wind.


Rhododendrons like a moisture retentive soil that is well drained. Amend soil with acidic wood compost or redwood soil conditioner to achieve a soil structure which is rich and fluffy. Beware of planting close to concrete foundations or other areas near concrete, as these sites tend to have higher ph soils that are toxic to rhododendrons. If your soil is heavy clay which collects and holds water, you must insure that the rhododendron’s roots stay well above this heavy, wet soil. Often, the simplest solution is to mound the soil up to give the rhododendron 18”-24” of clearance above the clay basin. Other possibilities are raised beds or rock garden constructions. Dig a hole 12” larger than the rootball and place the plant into the hole, making sure that the top of the rootball is a couple of inches above the surrounding ground. NEVER BURY THE PLANT DEEPER. A rhododendron fertilizer may be applied at the time of planting, being careful to follow directions on the package.


Mulch provides many important functions; it helps keep the roots cool and moist, keeps other plant competition in check, and helps to build a rich soil as it decomposes. The best mulches to use are: fir bark (mini or micro grade), pine needles, rotted sawdust or any other type of wood chips. Avoid newly chipped wood if it heats up in a pile. Usually it is best to allow fresh chips to age for a season before using near plants. Aged horse or cow bedding is quite good if it has been composted for a season, but it does tend to bring in weeds. Apply about 4 inches of material, beginning just outside the drip line and reaching in toward the trunk. DO NOT PILE MULCH AGAINST THE TRUNKS. Reapply mulch yearly to maintain this level. Never use weedmat around rhododendrons, because their roots require access to the air. Weedmat + Mulch = Suffocation! If you must use weedmat, keep it back at least to the drip line of the plant.


A regular feeding program will insure that your plants have the proper nutrients to keep them strong and healthy. To encourage the formation of flower buds, apply a granulated rhododendron specific fertilizer once in the early spring (February-March), then again in early summer (May-June). As soon as it has finished blooming, the rhododendron begins setting the buds for next year’s flowers, so this post-bloom feeding is especially important. We think “Valentine’s Day and Father’s Day” — an easy way to remember the two applications. In fall (November-December) use a mild, organic fertilizer to help keep the soil fertile, and insure that your plants have a steady supply of nutrients throughout the year. When applying fertilizer, gently scratch it into the mulch beginning six inches from the trunk, working your way out to the drip line. If you are going to apply more mulch, fertilize first then mulch on top. How much? We recommend 1 cup for plants less than 3 ft. tall, and 2 cups for plants larger than 3 ft. tall.


It is important to pinch out any single growth shoots on young rhododendron. This encourages multiple branching and prevents your plant from becoming ‘leggy’. A good rhododendron should have multiple branches close to the ground level, forming a well rounded plant. By keeping your plant ‘pinched’, you can encourage more branching, creating a fuller plant with more flowers! Heavier pruning can be done when necessary. Ask us for a demo.


For newly planted rhododendrons, irrigation in the dry months is essential to get your plants well established. Soil should be moist, but not soggy. Water requirements will vary from week to week, from one part of your garden to another. The best test is to get your fi ngers into the top 2-3” of soil and CHECK. A drip irrigation system must also be checked and adjusted regularly. Droopy leaves can indicate a thirsty plant, but they can also indicate a too-wet plant. Once your rhododendrons are established, they can get by with only occasional summer water.