The high amount of iron in clay soil makes it an ideal environment for planting azaleas, however, this substrate is also known for its ability to hold onto water due to its weight and volume.
For success with your azaleas you’ll need to alter the soil’s height and composition to prevent your plant from drowning.
Here are 10 key steps to ensure your azaleas will not only survive well in clay soil but thrive long after planting!
- Clay loamy soil
- Organic mulch
- Peat moss
- Small shovel
- Soil pH tester
- Landscape timbers/bricks
- Crushed rock/stones
1. Choose Your Planting Location Carefully
Azaleas perform best in a shady location protected from wind – a spot that receives full morning sun and afternoon shade or under a tree is ideal.
Full shade results in poor flowering while excessive sunlight can make azaleas vulnerable to lace bug infestations.
The Clemson University Extension specifically recommends planting “under pine trees since the acidic soil and moderate filtered shade prompts vigorous growth.”
2. Have Your Soil Tested
Slightly acidic soil (4.5-6.0 pH) provides ideal growing conditions for azaleas, so you should determine whether your soil is suitable by having your soil tested at your local extension office
Alternatively, you could place a high-quality soil meter/gauge into the substrate. I like this 3-in-1 sensor that monitors moisture and light levels in addition to providing Ph readings.
This provides a quick and accurate reading of the pH levels, allowing you to adjust accordingly before planting.
Most garden soil falls between 6.0-7.0 pH scale, so your soil may require little to no amendments, but it’s best to be sure.
3. Prepare a Raised Bed
Azaleas have shallow, hair-like roots that don’t do well in deep water-logged clay soil, so you’ll need to prepare a raised bed/mound for them on top of the native soil.
Create a bed 8-12 inches above ground level with the support of landscape timbers, bricks, or rocks and fill the area with a 50-50 mix of loose clay loam soil and peat moss.
4. Amend the Soil
To ensure the soil is within the ideal pH range and draining quality needed for azalea growth, amend the soil bed by adding some ericaceous (acidic) compost.
This is widely available at garden stores and will improve soil aeration. Mushroom compost is also a good option for improving clay soil.
Be sure to amend an area of the soil that is 2-3 times wider than the azalea root ball and the same depth.
Amending as large an area as possible will ensure that the roots spread into the surrounding soil instead of being restricted to the planting hole. Allow the soil bed two weeks to settle before planting.
5. Prepare Hole for Planting
Dig a wide, shallow hole (about half the height of the root ball) in the middle of the amended soil area. The azalea will need planting high above soil level to help the shallow roots grow and spread above grade.
Pat down the newly dug hole with your foot or by hand to give the plant a firm foundation to prevent it from sinking below soil level.
6. Perform Drainage Test
To check the soil for adequate drainage, fill the newly dug hole with 6 inches of water and wait 24 hours – if all the water has drained, your azalea is ready to be planted.
If it hasn’t drained after 24 hours, mark the water depth with a stick/dowel rod, making sure it is visible above the water line.
Wait for the water to drain or scoop it out and fill the hole with small stones or crushed rock up to the height of the stick to correct drainage issues.
7. Remove Azalea From Container & Gently Loosen Root Ball
Water your potted azalea 2-3 hours prior to planting for easier removal. As the roots are delicate and may be bound in the pot, carefully cup the top of the plant at the stem and tip the pot upside down.
If the root ball remains stuck in the bottom of the pot, gently tap the sides on a hard surface or enlist a second person to hold the pot while you tease the soil base free.
Next, use your fingers or a small shovel to gently loosen the roots and soil. If that doesn’t work, make 2-inch-deep cuts evenly around the sides of the root ball and loosen the potting soil from the roots.
8. Place Azalea Into Hole and Fill in With Amended Soil
Place the azalea into the prepared hole with the root ball sitting about 2-4 inches above the surrounding soil.
Backfill the space around the roots with the amended soil, and lightly tap the soil around the roots to ensure there are no air pockets.
Sonia Uyterhoeven at the New York Botanical Garden also recommends building a temporary raised edge of 3-4 inches around the perimeter of your root ball with excess soil and leaving it in place for 6-8 weeks.
“This acts as a reservoir that concentrates water in the root ball area.”
9. Water Well To Settle Soil
Water the planted area/reservoir a little at first, allowing it to subside before giving it a thorough second watering.
It will need an inch of water weekly (or a half of a gallon per square foot) until they are fully established, which can vary between 3-7 years depending on the variety.
Check on your azalea’s root ball every other day for the first 3 weeks to ensure it doesn’t dry out, and water as needed.
10. Spread Mulch
After planting and each year at the beginning of spring, add a 2-inch layer of mulch over the root ball.
Great mulch will consist of leaf mold (especially acidic-leaning oak and beech), compost, and well-rotted manure.
Mulch will increase soil fertility by replenishing nutrients lost in the soil throughout each season. It will also hold moisture, cutting down watering needs in the summer months.
Be sure to leave a gap between the mulch and the azaleas woody stem to prevent potential disease.
Care Tips for Growing Azaleas in Clay Soil
- Don’t use wood chips/bark as mulch as this depletes much-needed nitrogen in the soil, causing yellow foliage.
- Don’t add fertilizer as loamy clay soil amended with organic matter is fertile enough!
- Do consider using fine pine bark in your raised bed if planting azaleas in a hot climate. Root rot organisms can thrive in wet, humid conditions, but pine bark can help suppress Phytophthora root rot spores.
All in all, the process of planting your azaleas in clay soil will take 3-4 weeks from start to finish when you factor in soil and drainage testing, preparing the raised bed, and allowing the amended soil to settle.
If planted correctly, your azaleas should reward you with bushy (not leggy or scraggly) foliage and beautiful blooms for three weeks between February-September depending on your planting time and azalea variety.