Boxwood Cultivation: Intermediate Growing Techniques

Advanced Boxwood Growing

Building on basic knowledge, this intermediate guide explores the extensive world of boxwood cultivars, propagation methods, disease identification and management, and advanced techniques for formal garden creation.

Understanding Boxwood Diversity

Taxonomic Overview

The genus Buxus contains approximately 90 species:

Commercial Species and Hybrids

Cultivar Selection Guide

Disease-Resistant Varieties (critical in blight-prone areas):

By Landscape Purpose:

Propagation Techniques

Cutting Propagation

Primary method for boxwood:

Timing:

Cutting preparation:

1. Select current season's growth
2. Take 4-6 inch cuttings
3. Remove lower leaves (bottom 2 inches)
4. Wound base lightly (optional)
5. Apply rooting hormone (IBA 1000-3000 ppm)

Rooting environment:

Post-rooting care:

• Harden off gradually
• Pot up in spring
• Grow on 1-2 years before planting

Layering

Simple technique for home gardeners:

1. Select low branch
2. Wound bark on bottom side
3. Pin to ground, cover with soil
4. Keep moist
5. Sever when rooted (6-12 months)

Division

Possible for multi-stemmed plants:

• Best in early spring
• Ensure adequate roots on each division
• Plant immediately

Disease Management

Boxwood Blight (Calonectria pseudonaviculata)

The most serious threat to boxwood:

History: Arrived in U.S. in 2011 (NC and CT)

Symptoms progression:

Pathogen biology:

• Produces sticky spores in wet conditions
• Spreads by rain splash, tools, animals
• Can persist on dead leaves for years
• Optimal: 64-77°F, high humidity

Management strategies:

Fungicide options (preventive):

Volutella Blight

Secondary pathogen on stressed plants:

Symptoms:

• Salmon-pink spore masses on dead tissue
• Often follows winter damage
• Twig dieback

Management:

• Improve plant health
• Prune out affected branches
• Improve air circulation
• Avoid overhead irrigation

Root Rot (Phytophthora)

Symptoms:

• Yellowing, wilting
• Brown roots
• Plant decline

Prevention:

• Excellent drainage
• Avoid overwatering
• Raised beds if necessary

Pest Management

Boxwood Leafminer

Most common pest:

Management:

Box Tree Moth (Emerging threat)

Cydalima perspectalis - invasive from Asia:

Identification:

• Green caterpillars with black heads
• Black and white stripes
• White adult moths with brown borders

Damage: Complete defoliation possible

Management:

Boxwood Mite

Symptoms: Stippled, bronzed leaves

Management:

• Miticides if severe
• Horticultural oil (dormant)
• Encourage predatory mites

Advanced Pruning Techniques

Formal Hedge Creation

Establishing new hedges:

1. Plant at half mature width spacing
2. Allow to fill in before shearing
3. Shear sides at slight angle (wider at bottom)
4. Never shear during active growth
5. Time shearing for late spring

Maintaining formal hedges:

Thinning for Health

Dense interior creates disease-favorable conditions:

Technique:

1. Reach inside with hand shears
2. Remove small interior branches
3. Create air channels
4. Reduce density by 10-20%
5. Repeat annually

Topiary Training

Basic shapes:

Tools:

• Hand shears for precision
• Electric shears for large areas
• Frames/guides for complex shapes

Container Culture

Container Selection

Container Care

Winter Protection (Containers)

In Zones 6 and colder:

• Move to protected location
• Insulate pot with bubble wrap
• Or sink pot in ground for winter

Troubleshooting

Next Steps

1. Trial disease-resistant varieties
2. Practice propagation techniques
3. Master formal pruning
4. Develop disease scouting skills
5. Create topiary designs

Understanding these intermediate concepts enables successful cultivation of boxwoods even in challenging conditions.