Azalea care guide: when & how to prune, fertilize and spray

When: 3–7 weeks after the last spring frost.

• zones 3–5: about May 31 – Jun 28
• zones 6–7: about May 6 – Jun 3
• zones 8–10: about Mar 18 – Apr 15

This shrub sets next year's flower buds over the summer. Pruning within a few weeks after the flowers fade gives the most blooms next year. Prune later and you cut off the buds.

1. Wait until the last flowers have faded.
2. Remove dead, damaged and crossing branches first.
3. Renewal-prune: cut one-third of the oldest, thickest stems right down to the ground. Over three years this replaces the whole shrub with vigorous young wood.
4. Shorten overly long stems to an outward-facing bud or side branch to shape the shrub. Avoid shearing it into a ball.
5. Azaleas respond well to shaping. Cut individual stems back to a leaf cluster to keep plants compact.
6. For Encore reblooming azaleas, finish pruning by midsummer.

Tools: Bypass pruners, Hand shears

When: 3–7 weeks after the last spring frost.

• zones 3–5: about May 31 – Jun 28
• zones 6–7: about May 6 – Jun 3
• zones 8–10: about Mar 18 – Apr 15

A single spring feeding as growth starts covers most shrubs for the year.

1. Scatter fertilizer at the label rate from near the stems out past the drip line, where the feeder roots are.
2. Water it in thoroughly.

What to use: 🌿 Organic acid-loving plant food (e.g. Espoma Holly-tone 4-3-4) · Acid-forming fertilizer (e.g. Miracid 30-10-10 or ammonium sulfate)

When: 6–8 weeks before the first fall frost.

• zones 3–5: about Aug 6–20
• zones 6–7: about Aug 30 – Sep 13
• zones 8–10: about Oct 6–20

Late feeding pushes soft new growth that won't harden off before frost and gets killed back.

1. Don't apply any more fertilizer until spring. If you were planning one last feeding, do it now or skip it.
2. Keep watering as normal. Well-watered plants handle winter better.

When: 5–7 weeks after the last spring frost, then every 8 weeks (2 times a season).

• zones 3–5: about Jun 14–28
• zones 6–7: about May 20 – Jun 3
• zones 8–10: about Apr 1–15

Lace bugs hatch in late spring and can bleach a whole shrub's leaves by summer.

1. Turn over a few leaves. Look for tiny lacy-winged insects and black specks.
2. If you find them, spray the leaf undersides thoroughly with insecticidal soap or horticultural oil (summer rate).

What to use: 🌿 Insecticidal soap (e.g. Safer Brand) · 🌿 Horticultural / dormant oil (e.g. Bonide All Seasons Oil) · Acetamiprid (e.g. Ortho Flower, Fruit & Vegetable Insect Killer)

When: 3–8 weeks before the last spring frost.

• zones 3–5: about Mar 15 – Apr 19
• zones 6–7: about Feb 18 – Mar 25
• zones 8–10: about Dec 31 – Feb 4

This plant prefers a pH of 4.5–6.0. A soil test tells you whether you need lime, sulfur or extra nutrients, so you aren't guessing.

1. Take 6–8 small samples from the root zone, 4–6 in (10–15 cm) deep, using a clean trowel.
2. Mix them in a clean bucket, let the soil air-dry, and send about 2 cups to your local extension office or a soil lab. A home kit works but is less accurate.
3. Follow the lime or sulfur amounts in the report. Change pH slowly: no more than 1 unit a year.

Tools: Clean trowel, Plastic bucket, Soil test kit or lab mailer

When: 2–6 weeks after the last spring frost.

• zones 3–5: about May 24 – Jun 21
• zones 6–7: about Apr 29 – May 27
• zones 8–10: about Mar 11 – Apr 8

Mulch keeps roots cool and moist, suppresses weeds and slowly feeds the soil. Applying it after the soil warms lets roots wake up first.

1. Spread 2–3 in (5–7 cm) of mulch over the root zone.
2. Keep mulch 2–3 in (5–7 cm) away from stems and trunks. Mulch piled against bark invites rot and rodents.
3. Don't go deeper than 3 in (7 cm) in total. Too much mulch suffocates roots.

What to use: 🌿 Pine straw or pine bark fines (slightly acidifying) · 🌿 Shredded hardwood or pine bark mulch