Posted by Brent Wilson on 8/18/2016 to Fertilizing & Watering Tips
A little good advice goes a long way when it comes to success with growing the beautiful deciduous rhododendrons, commonly called native azaleas by many gardeners. When planted right, and in the right spot, native azaleas are exceptionally easy to grow.
I hope this article provides the helpful tips and instructions you need to plant and grow native azaleas like pros.
Here's a breakdown of what you need to know...
In The Ground
Native Azaleas are adaptable to many soil types but prefer a moist, well-drained soil that is rich in organic matter. Though some native azaleas are tolerant of boggy soils, as with so many other ornamental plants, constantly soggy or wet soil can be problematic for other varieties. So make sure to know the specific soil moisture needs for the native azalea variety you intend on planting.
How To Test Soil Drainage
If you are uncertain about soil drainage in the area you intend to plant your native azalea, it's well worth taking the time to test the drainage before planting. To test soil drainage, dig a hole 12" wide by 12" deep in the planting area. Fill the hole with water and let it drain. Then, after it drains, fill it with water again, but this time clock how long it takes to drain. In well-drained soil the water level will go down at a rate of about 1 inch an hour. A faster rate, such as in loose, sandy soil, may signal potentially dry site conditions and a need to add some moisture retentive organic matter. A slower rate indicates poor draining soil and is a caution you need to improve drainage, plant in a raised mound or bed, or look for plants that are more tolerant of wet or boggy conditions.
Native azaleas are excellent candidates from container culture. When growing in pots they appreciate a moist but well-drained soil. Constantly soggy soil can and often will cause root rot or other harmful or deadly plant diseases. Therefore, choose a pot with a drainage hole(s) and use a good potting soil or potting mix, or a 50/50 mix thereof for planting. Avoid the use of native soil. You can add about 10 to 20 percent perlite or pumice to the soil mixture to help with drainage
Native Azaleas grow best in an acid to slightly acidic soil ranging between 4.5 to 6.5 on the pH scale. Most average garden soils fall between a pH range of 6.0 to 7.0.
Testing Soil pH
Soil pH is a measurement of the alkalinity or acidity of soil and is measured on a scale of 1-14, with 7 as the neutral mark. Any measurement below 7 indicates acid soil conditions, and anything above 7 indicates alkaline. If you're unsure about the pH of your soil, or whether or not it's suitable for growing Native Azaleas, it's a good idea to test the soil pH in the planting area. You can quickly test soil pH with an inexpensive soil pH tester probe. To raise the pH (make more alkaline) you can add pelletized limestone to the soil. To lower the pH (make more acid) you can apply Soil Sulfur, Aluminum Sulfate, or Chelated Iron. Adding organic compost to the soil or using compost as mulch can also help to increase acidity and maintain acid soil conditions.
Learn More: What is Soil pH and How To Adjust It?
Native azaleas prefer life on the shady side. In their native habitats you'll find them growing in or on the edges of woodland areas. Shelter from direct afternoon sun is recommended. Morning or all-day heavily filtered sun or all-day dappled shade is fine.
Planting A Native Azalea
Scroll down for container planting instructions and care tips
Start by digging your planting hole at least two to three times as wide and not much deeper than the rootball. The wider the hole the better. Place native soil removed from planting hole around the perimeter of the hole, in a wheel barrow, or on a tarp.
Depending on the type, fertility and porosity of the soil in the planting area you might need to amend the native soil. When planting a native azalea in heavy clay, or other compacted or poor soils, it is beneficial to thoroughly mix in some good organic matter such as composted cow manure, mushroom compost, and/or a good planting mix at a 50/50 ratio with the native soil removed from the planting hole. When planting in very sandy, quick-draining soil you might want to consider mixing in some top soil, peat moss and/or compost to help retain moisture. When planting in fertile, moist but well-drained soil there is no need for adding a soil amendment, though some composted organic matter might be beneficial.
To remove your native azalea from the nursery pot it was growing in, firmly grasp the base of the plant and very gently try to lift and remove it from the pot. If the root ball is stuck in the pot, lay the plant on it's side and tap on the side of the container. If this doesn't work to loosen the rootball use snips to cut the container away. After having removed the plant from the container, loosen some feeder roots around the surface of the root ball. If root bound, you can spray the sides and bottom of the root ball with a stream of water from a garden hose. This will help to wash away some soil from the exterior of the root ball making it easier to loosen roots.
If you are planting in well-drained soil set your native azalea in the planting hole so that the top edge of the rootball is at or slightly above ground level, to allow for settling. If your soil is moderately drained (drains at less than 1-inch per hour) the top of the root ball should sit 2 to 4 inches above ground level, as shown in the planting diagram below. If necessary, add some backfill soil mixture to the bottom of the planting hole to achieve proper planting height.
Note: If the soil is poorly drained (constantly soggy or wet) either improve soil drainage in the planting area or choose a different plant species more tolerant of wet soils.
After setting your native azalea in the planting hole, use one hand to hold the plant straight and your other hand to begin pulling your soil mixture around the root ball, tamping as you go to remove air pockets. When you have filled the hole to the halfway point you can soak the soil. Then continue back-filling to the top edge of the root ball. If you are planting higher than ground level taper your soil mixture gradually from the top edge of the root ball to the ground level, as shown in the planting diagram above. To avoid suffocating your plant, avoid placing any soil on top of the root ball.
Step 6 (Optional)
When planting your native azalea in a location far from a water source, and in well-drained soil, you can use remaining soil mixture to build a water retaining berm (catch basin/doughnut) about 2 to 3 inches high around the outside perimeter of the planting hole. This basin will help to collect water from rainfall and irrigation reducing the need for hand-watering. The berm can be removed after a growing season or two.
Next, deeply water the planting area, including the root ball, to a depth equal to the height of the root ball. For an extra boost, to reduce plant shock and promote greener, more vigorous plants by stimulating early root formation and stronger root development, you can also water you newly planted native azalea with a solution of Root Stimulator.
Spread a 1- to 2-inch layer of shredded or chipped wood mulch or a 3- to 4-inch layer of pine straw around the planting area to conserve moisture and suppress weed growth. As the mulch decomposes it will add vital nutrients to the soil that your native azalea will appreciate. Avoid the use of freshly chipped or shredded wood for mulch until it has cured in a pile for at least 6 months, a year is better. Avoid placing or piling mulch directly against the base of your plant as this could cause the bark to rot.
Planting A Native Azalea In A Pot
Native azaleas growing in pots appreciate a moist but well-drained soil. Constantly soggy soil can and often will cause root rot or other harmful or deadly plant diseases. Therefore, choose a pot with a drainage hole(s) and use a good potting soil, or potting mix, or a 50/50 mix thereof. Avoid the use of native soil. You can add about 10 to 20 percent perlite or pumice to the soil mixture to help with drainage.
Also make sure to choose a container that is large enough to allow for 2 to 3 years of growth before having to shift up to a larger size container. This might mean your planting pot would be 6 inches or more in width than the root ball of your plant.
Container color will matter as well. Not only will you want to select a color of container that goes well with the flower and foliage color of your native azalea, you'll also want a container that matches the style of your home or other structures or plants in the surrounding environment.
Many nursery & garden centers offer a wide variety of containers to choose from. Before heading out to buy a container take pictures of your home and the surrounding environment. Doing so will help you to choose just the right color and style.
Container Planting Instructions
Before filling your container with the soil mix, we recommend lining the bottom with shade cloth or a porous landscape fabric. This will keep the drain holes from becoming stopped up with soil. If you place gravel, stones or other materials in the bottom of your pot lay the fabric on top of it.
To remove your native azalea from the nursery pot it was growing in, firmly grasp the base of the plant and very gently try to lift and remove it from the pot. If the root ball is stuck in the pot, lay it on it's side and tap on the side of the container. If this doesn't work to loosen the rootball use snips to cut the container away. After having removed the plant from the container, loosen some feeder roots around the surface of the root ball. If root bound, you can spray the sides and bottom of the root ball with a stream of water from a garden hose. This will help to wash away some soil from the exterior of the root ball making it easier to loosen roots.
Pour a small amount of your soil mixture in the bottom of the container. Set your plant in the container and make necessary adjustments by adding or removing some soil so that the top edge of the root ball will sit 1/2 to 1" below the rim of the container.
Begin filling the container with your potting soil, tamping as you go, until the level of potting soil is even with the top edge of root ball.
Water thoroughly until water starts to drain from the holes in the bottom of the container. Add more potting mix if settling occurs during watering.
Step 6 (Optional)
Apply a 1/2" layer of wood chips or sphagnum moss to soil surface to help conserve moisture.
How To Care for Native Azaleas
How To Fertilize A Native Azaleas
Native azaleas will benefit from fertilization. I feed mine after they bloom in spring with an acid-forming fertilizer such as azalea, camellia & rhododendron food or a slow-release shrub & tree food, preferably one that contains Sulfur and/or Iron. Alternatively, you can feed with a natural organic plant food. To avoid stimulating new growth that could be damaged by an early frost, cease fertilization after August.
Native azaleas grow best in an acid to slightly acid soil ranging between 4.5 to 6.5 on the pH scale. Most average garden soils fall between a pH range of 6.0 to 7.0.
Learn More: What is Soil pH and How To Test & Adjust It?
How To Water Native Azaleas
Native azaleas prefer a moist but well-drained soil. That said, they are tolerant of dry periods when established. As with so many other ornamental plants, constantly soggy or wet soil can be problematic. So make sure not to over-water your native azaleas!
At Planting Time
Immediately after planting deep soak the soil in the planting area, including the rootball, to a depth equal to the height of the root ball. For an extra boost, you can water your newly planted native azalea with a solution of Root Stimulator, which stimulates early root formation and stronger root development. Root Stimulator reduces plant shock and promotes greener, more vigorous plants
During the First Active Growth Season
In average garden soil you should not have to water your newly planted native azaleas every day. More often than not, this causes soggy soil conditions that can lead to root rot and other plant diseases. In the absence of sufficient rainfall, water only as needed to keep the rootball and surrounding soil damp to moist. Keep in mind that deep soaking less frequently and allowing the soil to dry out somewhat before watering again is much better than splashing just a little water on the plants every day.
Note: When planted during the winter dormant season, when native azaleas are not actively growing and evaporation is much slower, plants not require as much water. So, be extra careful not to overwater during winter!
When established, native azaleas are quite drought tolerant. That said, wilting new leaves or new stems bending over during a dry period are indicators that your plant might need a good deep soaking. Always check soil moisture before watering.
Note: When watering with an automated irrigation system it's best to set your timer to water during the early morning hours and not in the late evening or at night, which can lead to the onset of fungus and other foliage diseases. During the first few weeks after planting, check soil moisture often and adjust irrigation time if necessary to keep the soil moist, not wet.
How To Prune Native Azaleas
Native azaleas are deciduous woodland shrubs or small trees admired for their natural form and beauty. Therefore, I generally recommend very little if any pruning. Native azaleas should not be pruned as heavily as your evergreen azaleas. They do not recover as quickly and you could stunt your plant. That said, native azaleas can be pruned to control size or to form a small tree.
When to Prune
Most important, don't forget that the spring blooms on native azaleas came from buds that formed the previous summer. Therefore, avoid pruning during summer, fall or winter. That said, selective pruning to remove a stray or damaged branch that is spoiling the shape of the plant can be done any time of year. Any significant pruning to control size, or to form a tree, should be done in late winter, while the plant is dormant, or immediately following the spring bloom cycle.
How to Prune
After Spring Bloom When pruning a native azalea immediately after it has bloomed use a sharp pair of bypass hand pruners to remove any damaged or dead branches. At this time, I usually only cut back the longer live branches that are spoiling the look and shape of the plant. Make cuts at a point just beyond the main form of the plant. Established plants that have outgrown the space they were intended to fill can be cut back by up to a third of their height to control size and form a more dense plant.
Pruning For Tree Form
Taller growing native azaleas (6' or more in height) can be pruned to form a very attractive small tree. Tree-forming may also help to rejuvenate older native azaleas. The goal in tree-forming is to form a nice canopy of branches and foliage on top of what is usually one to several exposed lower trunks.
This type of pruning should be done in late winter or immediately following bloom in early spring.
When tree-forming a native azalea you'll be removing lower branches. However, before removing any branches, study the plant and try to visualize the end result after pruning.
I usually don't recommend removing main trunks. However, sometimes doing so is necessary to achieve balance and the look you want. If you intend to remove a trunk(s) it will need to be cut off as close to the ground or base of the plant as possible.
Note: Before removing any main trunks make sure that doing so will not spoil the shape of the canopy.
After you've selected and removed any unwanted trunks, you can begin removing lower branches that stem from the trunk(s). Start by removing lateral branches growing from the trunk(s) that are lowest to the ground. When removing a branch, make your cut as close to the trunk as possible but without cutting into the bark. After each cut, take a step back to take a look at the tree. Continue removing lower branches upward to a desired height that is satisfying in appearance.
Note: The use of pruning sealer is not necessary though you may use it if you want.
Plant Long & Prosper!
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