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

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

Tightly sheared boxwood traps humidity inside, which sets up blight. Thinning lets light and air in.

1. Reach into the shrub and cut out 3–6 in (8–15 cm) sections of branches here and there, making small 'holes' across the outer shell.
2. Remove dead wood and fallen leaves trapped in the crotches.
3. Disinfect pruners with 70% alcohol between plants.

Tools: Bypass pruners, Rubbing alcohol

When: 4–8 weeks after the last spring frost.

• zones 3–5: about Jun 7 – Jul 5
• zones 6–7: about May 13 – Jun 10
• zones 8–10: about Mar 25 – Apr 22

Shearing once the new growth hardens keeps a crisp shape without stressing the plant.

1. Trim this year's new growth back by about half, leaving some.
2. Keep the base wider than the top so light reaches the lower branches.
3. Rake up and remove the clippings.

Tools: Sharp hedge shears

Caution: Don't shear after midsummer. Late new growth gets winter-burned.

When: from 1 week before to 3 weeks after the last spring frost.

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

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: 🌿 Balanced organic granular fertilizer (e.g. Espoma Plant-tone 5-3-3) · Slow-release balanced fertilizer (e.g. Osmocote Smart-Release 14-14-14)

When: 2–4 weeks after the last spring frost, then every 2 weeks (4 times a season).

• zones 3–5: about May 24 – Jun 7
• zones 6–7: about Apr 29 – May 13
• zones 8–10: about Mar 11–25

Boxwood blight spreads fast in warm, wet weather and can't be cured once it's in the plant.

1. Only needed if boxwood blight has been found in your area, or on your plants before.
2. Spray all foliage thoroughly ahead of rainy periods, every 7–14 days.

What to use: 🌿 Bacillus-based biofungicide (e.g. Serenade or Cease) · Chlorothalonil (e.g. Daconil Fungicide)

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 6.5–7.2. 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: from 1 week before to 4 weeks after the first fall frost.

• zones 3–5: about Sep 24 – Oct 29
• zones 6–7: about Oct 18 – Nov 22
• zones 8–10: about Nov 24 – Dec 29

Evergreens keep losing water through their leaves all winter. Going into winter well hydrated prevents winter burn (brown, scorched foliage).

1. If autumn has been dry, give a slow, deep soak: about 10 gallons (40 L) per inch of trunk diameter, or 1 in (2.5 cm) of water across the root zone.
2. Repeat every 2–3 weeks until the ground freezes.
3. Optionally spray an anti-desiccant (e.g. Wilt-Pruf) on a mild day above 40°F/4°C.