How to Plant Azalea Bushes


Azaleas are breathtaking and are easy to raise when planted properly. Are you planting it correctly?
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After a long, cold winter, the spring garden comes to life. Spring bulbs, of course, are important players, as are flowering trees and shrubs like forsythia, magnolia, and lilac. Perhaps the most breathtaking of all are azaleas.

Azaleas (Rhododendron spp.) enchant us every spring with their fragrant, funnel-shaped flowers in a rainbow of colors. You can grow varieties with red, orange, pink, purple, yellow, or white flowers, with thousands of cultivars to choose from.

There are two general types. The deciduous varieties are indigenous to the United States. The evergreen varieties are native to Japan.

These shrubs have particular requirements and require specific conditions to thrive. If you can give them the environment they need, you can enjoy these beautiful shrubs in your own garden.

The Ideal Conditions

Temperature Requirements

Deciduous varieties thrive in the southeastern or south-central United States, where they are native.

USDA hardiness zones 6 to 8 are ideal for them, though they can withstand winter temperatures as low as -10°F (-23°C). Some varieties, such as the Northern Lights series, are even more cold tolerant.

Evergreen types are also hardy in zones 6 to 8, and Western azaleas thrive on the west coast of the United States.

Vibrant petals of a bush in full bloom

Azalea Light Requirements

These shrubs thrive in dappled or filtered sunlight, growing happily under tall deciduous trees or at the edge of a woodland.

If you do not have a wooded property, you can grow them in a location where they will receive no more than 4 to 6 hours of full, direct sunlight per day. It’s best if they get their sun in the morning and spend the afternoon in the shade. A location on the east side of the house would be ideal.

Deciduous varieties can tolerate more sun, while evergreen varieties require more shade. No azalea can grow in complete shade; they will not flower. Too much sun can cause sunburned leaves and flowers that fade quickly.

Beautiful pink azaleas under the heat of the sun

Soil Requirements

Azaleas have shallow roots and do not do well with “wet feet.” They require moist, acidic soil that drains well. A loamy soil with a high organic matter content is ideal.

Here’s how to test the drainage of your soil. Make a 12-inch-wide, 12-inch-deep hole. Fill the hole halfway with water and allow it to drain completely. Fill the hole again and measure how much water is in it every few hours. You can use a yardstick or a ruler. When the water level in your soil drops at least 1 inch per hour, you know it’s well-draining.

An orange traffic cone ass marking for a deep ground hole

If your soil does not drain well, mixing in a lot of organic matter in the form of well-rotted compost and leaf mold will help. Spread 4 inches of compost over the area where you will be planting. Then dig about 12 inches down, turning the soil over to fully incorporate the compost.

Do not dig a hole and then fill it with amended soil. That’s like trying to grow your shrub in a flower pot. Roots will not spread into the surrounding soil.

Azaleas require acidic soil with a pH of 4.5 to 6. Keep in mind that the number 7 is neutral. If the pH of your soil is too high, use ferrous sulfate instead of aluminum sulfate to lower it. Aluminum is toxic to azaleas. Before and after adding any amendments, perform a pH test.

If your garden soil does not meet an azalea’s pH, organic matter, and composition requirements, you can try growing them in raised beds 12 to 14 inches high. Keep in mind that even if your raised bed contains a lot of acidifying ingredients, areas with alkaline soils tend to have alkaline water. You should check the pH of your bed at least once a year.

It’s time to plant your new azalea after you’ve determined the best location in your garden for it and tested and amended the soil based on the results of that test. Make sure you give them enough space to grow.

A gardener wearing gloves during tree planting

9 Tips for Successful Planting

  1. Plant at the appropriate time of year. It is best to plant in the fall. This allows the shrub to settle in and begin growing roots during the autumn’s warm days and cool nights. Planting can also be done in early spring while they are still dormant. Avoid planting when the bushes are in bloom or during the summer heat.
  2. The soil should be tested and prepared. Check the pH and drainage of your soil and make any necessary adjustments.
  3. Plant at the appropriate depth. Dig a hole that is as deep as the nursery pot or burlap ball and about 6 inches wider.
A person putting some compost fertilizer while planting a tree
  1. Examine the root system of your new shrub when you remove it from its container. Trim any tangled or circling roots you find. If your plant is in a pot-bound, make a few small slices up and down the sides of the root ball with a garden knife.
A man pruning bonsai roots using gardening scissors
  1. If your azalea is balled and burlapped, you don’t need to remove the “burlap” unless it’s made of plastic or nylon. Natural burlap and jute rope will decompose. Once the plant is in the hole, cut the rope wrapped around the plant’s crown and loosen it. You don’t have to remove it completely, but make sure that all of the burlap and rope is tucked into the soil.
  2. Set the plant down in the hole. Check that the plant’s crown (where the branches and roots meet) is level with the soil. Tamp down any soil you added if you dug too deep. As the soil settles, this will keep the shrub from sinking.
  3. Backfill with soil and firmly tamp it down. Check that the crown is not covered by soil.
  4. Water thoroughly. To help the soil settle, water slowly and gently. Check on your new shrub every few days to see if it needs watering, especially if the weather is hot, sunny, or dry.
  5. Lay down a layer of mulch. Use organic mulches that mimic the forest floor, such as leaf mold or pine straw. Mulch cools the soil, prevents weed seeds from germinating, and adds nutrients to the soil as it decomposes. Spread a 2-3 inch layer around the shrub’s base, leaving a few inches of bare soil around the plant’s crown. Don’t pile mulch on top of the plant.

Ongoing Care for Azaleas

Watering Frequency 

These shrubs require about one inch of water per week, which can come from rainfall or from your garden hose. Deeply irrigate. Plants respond better to a single long, slow soak than to several short sprinklings. 

If the plant is dehydrated, the leaves of the azalea will wilt. Fortunately, the leaves wilt before the shrub completely dries out, giving you plenty of time to water.

An irrigation system installed in a garden for watering plants and trees

Fertilization

Azaleas are not heavy feeders. Established bushes that have been mulched with organic materials do not require fertilization.

If you must fertilize, do so in the late fall to early spring when the plants are dormant. If you have to amend your soil to make it more acidic, there are commercial fertilizers explicitly designed for acid-loving plants.

As with all plants in your garden, it’s best to conduct a soil test before applying fertilizer to determine which nutrients need to be replenished. Fertilizing when it isn’t necessary can cause root and leaf burn and is a waste of money.

Mulching

Mulch decomposes over time. Plan to replenish your mulch every year or two, but don’t pile it up. Keep the mulch layer between 2 and 3 inches thick. If it’s any deeper, water will be unable to reach your shrubs.

Alaine Connolly
Alaine has been working way too hard in horticulture since 1992, beautifying golf courses, resorts, and hotels. She is a part time landscape designer who works full time caring for a 28,000 square foot public garden. At home, she maintains her own 400 square feet plot. Alaine lives in northern Illinois - zone 5b.
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