Rhododendrons or “rhodies”  are shrubby plants that can form beautiful framework of a flowering garden. There are thousands of varieties of rhododendrons in all sizes. Growing rhododendrons lights up the landscape with spectacular blooms throughout the spring and fall season. All azaleas are actually rhododendrons. (But all rhododendrons are not azaleas – got it?) Both the taller rhododendrons and the more compact azaleas can thrive with a few growing tips.

1. They love filtered shade – but they need some sun to bloom best

In general, growing rhododendrons with small leaves (like the PJM rhododendron) like more sun than large leaved rhododendrons. The north or East side of a building or fence is ideal. Try to avoid the dry soil under the eaves of the house. Rhodies love a woodland setting under the filtered shade of taller trees.

2. Give them acid soil – but no aluminum sulphate

In areas of high rainfall the soil will naturally be acidic and growing rhododendrons is easier. In dry climates you may want to do a soil test to be sure your soil pH (the measure of acidity) is between 4.5 and 5.5. Garden centers sell DIY soil tests that are easy to use. If your soil is not in the pH range to make rhododendrons happy you can make your soil more acid by adding pine needles, sphagnum peat moss or agricultural Sulphur to the soil at planting time.

Note: Do not use aluminum sulphate, often sold as a product that makes hydrangeas turn from pink to blue. It interferes with the growth of rhododendrons and azaleas.

3. Make sure you mulch – but don’t make volcanoes around the trunks

Rhododendrons have shallow, dense and thirsty roots. A mulch of wood chips, pine needles or compost will seal in moisture and slowly feed the plants. Use two to five inches of mulch on top of the roots but do not pile the mulch up around the trunk of the plants like a volcano. Pull the mulch a few inches away from the bark so that no mulch is touching the trunk. This helps to prevent disease and allows air into the soil.

4. Give them room – but protect from wind

The evergreen foliage of rhododendrons will dry out quickly if hit by warm summer winds and rhododendrons also suffer damage from cold winds in winter. Allow space for good air circulation between plants by planting two to five feet apart from other trees and shrubs. A sheltered spot near a hedge, clump of trees, fence or building will help to buffer those damaging winds and aid in growing rhododendrons.

5. Keep the soil moist – but don’t let roots set in water

In most gardens rhododendrons will need extra water in the summer. The soil must be kept moist year round. The secret to getting the “moist but well drained” soil that so many woodland plants love is to add organic matter to the planting area. Shovel and work into the soil up to 50% peat moss, compost or bark mulch. Mix this not just into the planting hole, but into the area three feet all around the shrubs.

When planting, dig a hole twice as wide as the root ball of the new plant. Rhododendrons can suffer from root rot if the soil is heavy clay or if the soil is in a low spot that collects water. If you need to check for good drainage, pour a bucket of water into the planting hole that you dig for your new plant. If the water disappears after a few hours, your soil is draining well.