Planting Azaleas in the Fall

Azaleas can be planted in fall or spring

Bill Sevier: Ask a Master Gardener

Saturday, October 15, 2016

Q: What time of the year is it best to plant azaleas? How best to plant them? K.D., Tulsa

A: Ideally, azaleas should be planted either in early spring or in fall after it cools. Either time is acceptable.

When planting in fall, it is suggested that you delay mulching until after the first frost so the plants will be assured of developing dormancy for winter.

Azaleas have some cultural needs that are a bit different from many other shrubs, at all times of the year. The chief difference is that they need an acidic soil, with a preferred pH (measure of acidity) in the 4.5 to 5.5 range. Our native soils do not normally have this degree of acidity, so some adjustments are usually needed.

To determine soil acidity, along with information about the nutrients nitrogen, phosphorus and potassium, have a soil test performed before planting. Instructions on how to perform a soil test and also how to plant azaleas may be found on the Master Gardener website.

If more acidity is needed, there are two options. The best option is to mix peat moss 1:1 or 1:2 with native soil. Peat moss is acidic and will usually produce an adequate pH. Another way to add acidity is to use elemental sulfur (pure sulfur) and mix it into the soil. The amount of sulfur to add depends on the pH, but a safe amount to use would be 7 tablespoons for every 10 square feet of soil. Sulfur will not immediately lower pH; it takes a few months for this to occur.

Azaleas have fine, shallow net-like roots. To plant them, create a blunt cone of soil, spread the roots out over the cone like an umbrella and cover with several inches of soil.

In well-drained soils, plant azaleas at the same level as they grew at the nursery — never deeper. If your soil is heavy clay, as it often is, it is best to plant above ground in a large mound of prepared soil. Spread the roots out and plant them on top of the mound, with a few inches of soil for cover.

In both cases, they should receive generous amounts of loose mulch at the time of planting and yearly thereafter. There is no best mulch. Any mulch that is loose is useful. Contrary to popular belief, there is no mulch that will add acidity to the soil.

All the plants need generous irrigation during establishment and subsequently in all seasons.

A slow-release fertilizer, such as Osmocote, may be mixed with the soil at the time of planting and, if so, no further fertilizer will be needed the rest of the following growing season. Azaleas, in general, need less fertilizer than other shrubs and will suffer if excessively fertilized. If mulched yearly, adequate nutrients may be supplied by the decaying mulch.

Garden tips

• Peonies, daylilies and other spring-flowering perennials should be divided or planted now.

• Dig and store tender perennials like dahlias and caladiums in a cool, dry location. Cannas and elephant ears can also be dug, but most will survive the winter fine if mulched heavily and in a sheltered area.

• Plant fall mums and asters, and keep them watered during dry conditions. Don’t crowd because they take a couple of years to reach maturity.

• As leaves begin to drop, keep them off any newly seeded fescue lawns