How And When To Fertilize Azaleas: Learn How Smart Feeding Can Boost Your Blooms

Azaleas are a popular evergreen choice for shady areas such as in foundation plantings. The spectacular show of spring flowers covers the shrubs with long-lasting blooms often regaled at azalea festivals. To grow azalea shrubs and keep them in tip-top shape, learn the best way to fertilize azaleas.

Azaleas are in the genus Rhododendron and are either deciduous (drop their leaves in fall) or evergreen. They can be native or non-native and through extensive hybridization, almost 10,000 varieties exist. While most types of azaleas burst forth with their biggest display in spring, Encore azaleas rebloom several times during the summer, but not as fully.

The best way to fertilize azaleas is to let nature lead the way. Examine the shrubs regularly for signs that certain nutrients may be low. When needed, organic fertilizer is often the best choice.

How To Tell If Azaleas Need Fertilizer

If the azalea planting bed is rich with compost, well aerated, well draining, and slightly acidic (5.5-6), established azaleas do not need fertilizer. Azaleas have long feeder roots that stretch out several feet from the shrub, picking up the vital nutrients that nourish the plant.

Mulching azaleas with organic mulches, such as composted pine bark, pine needles, oak leaves, or straw, enrich the soil as they decompose, further reducing the need for fertilizer.

If nutrient problems do arise, choose an organic source to remedy the situation. Here are common nutrient issues and what to apply:

• Leaf chlorosis is characterized by leaves that are yellow to white with green veins. It is usually caused by a high pH that prevents the uptake of iron. To lower the pH, apply ferrous sulfate, ground sulfur, or iron chelate to the soil. For a temporary boost, you can spray the leaves with iron chelate.
• Pale green or small leaves could mean the plant needs nitrogen. Blood meal fertilizer is an organic source of nitrogen that can be applied according to directions.
• Yellow mottling on the edges of leaves indicates too much potassium, so avoid its use.
• Small, dark green leaves with dead tips could indicate a need for phosphorus. Add bone meal fertilizer to the top of the soil and lightly scratch it in, avoiding the delicate feeder roots.
• Yellowing leaves that drop, particularly in the center, are normal and result from shading of the shrub’s interior.
• Browning branches during the season usually indicate winter injury. Cut off the dead wood and consider replacing the plant with a variety of cold hardy azalea in your area.

How To Fertilize Azaleas

If a soil test shows azalea shrubs need a general fertilizer, the best time to apply it is in late winter to early spring. Avoid adding fertilizer after July 1 because it may stimulate new growth that will not be hardened off before winter.

Different types of organic fertilizers benefit azaleas by their slow, extended release of nutrients. Organic choices that supply nitrogen, phosphorus, potassium, plus trace elements include fish meal, canola meal, worm castings, and powdered alfalfa. Always read and follow label instructions.

If you choose to go the conventional, chemical fertilizer route, a good fertilizer for azaleas is specially formulated for acid-loving plants. The granular, extended-release form is convenient and can be applied in spring.

Avoid using lime or alkaline fertilizers because they will increase the soil pH.

Do All Azaleas Need The Same Kind Of Feed?

While most azalea shrubs benefit from organic fertilizer when needed, Encore azaleas bloom off and on all season and follow a different fertilizer regimen, according to the developers. They recommend fertilizing right after the first spring bloom using a balanced, slow release, granular fertilizer suitable for azaleas and camellias. If you have a long growing season, you may want to add another application in mid-summer but never after Aug. 1.

For an extra boost, they recommend applying liquid fertilizer directly to the foliage and root area, following package directions.

Homemade Fertilizers For Azaleas

Some people like to create their own azalea fertilizer by combining different organic fertilizers with soil amendments for an extended release of nutrients each spring. DIY Liquid fertilizers utilize common household ingredients and scraps and can be nice general fertilizers.

Risks Of Over-Fertilizing Azaleas

Over fertilizing azaleas can damage the tiny feeder roots that form a large network underground. A surplus of nutrients also can bring more azalea pests like lace bugs and whiteflies. Overfertilizing can cause fertilizer burn in azaleas and other plants.

A soil test is a good way to determine if the plants need fertilizer. Your county extension service offers soil testing at a reasonable rate.

Frequently Asked Questions

More Azalea Ideas

• Azaleas doing well, but need a trim? Learn more about how and when to prune azaleas, according to gardening experts.
• Find the perfect pruning and trimming set in the Gardening Know How Shop to make your azalea shrub maintenance easy and effective.
• After you have pruned your azalea shrub, use those azalea cuttings to propagate new plants! You can have endless azaleas for years to come.
• Sign up for the free Gardening Know How Newsletter for more ideas and advice delivered straight to your inbox.

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