Chapter 79 Buxus microphylla, B. sempervirens

79.1 Boxwoods

The two main species are Japanese boxwood (B. microphylla) and common, or European boxwood (B. sempervirens).

A well-styled boxwood less than eight inches high that still evokes a sense of age and wild lands. Link to original image

79.2 Soil: General Deciduous / Rich Conifer Mix

Ratio: 3 parts bark, 1 part grit

Add-ins: dolomitic limestone (~5 lbs/yd), Tree-Tone (15 lbs/yd)

pH: ~6.5 (slightly below neutral)

Moisture: Average.

79.3 Moisture

Boxwoods likes regular water but need good draining. Avoid overly wet roots; excess moisture can cause root rot.

79.4 Light

Can tolerate low light, but does best in half-day sun to full sun. Mid-day shade keeps the roots cool and prevents the leaves from bronzing and burning.

79.5 Cultivation Notes

79.5.1 Potting

Boxwoods naturally have mats of fibrous roots rather than large woody roots. Roots should be combed out slightly to open up the mat, then wedges cut out to provide space for new roots to grow. Do not remove more than 1/4 of the total root mass.

This boxwood has been lifted and the soil partly removed to show how even yound boxwoods can create the appearance of great age. This particular specimen is probably less than 15 years old, yet some judicious pruning to open up the center has created an illusion of a much older (and larger) tree, Link to original image

79.5.2 Pruning

Heavy branch pruning should be done in late winter or early spring before new growth appears. Maintain shape through the summer by pinch pruning or clipping soft green stems with scissors. Do not clip through the leaves. Keep the center relatively open to prevent leaf die-back.

79.5.3 Feeding

Does better on a lighter feeding schedule. Feed in fall with an organic fertilizer like cottonseed meal, or a granular urea-based 10-6-4 fertilizer.

79.5.4 Pests & Problems

Soft growth is susceptible to leaf miners. Systemic insecticides can kill the miners, but it is easier to prune out infected leaves. Aphids are a problem occasionally; they can be controlled with insecticidal soap.

79.5.5 Winter Storage

These trees have shallow roots so are susceptible to hard freezes and wind burn. Protect from wind, and mulch heavily to keep the roots from freezing.

79.6 Propagation Notes

Propagate by stem cuttings which root easily.

79.7 Artistic & Styling Notes

Boxwoods are extremely brittle. I avoid bending and wiring branches as much as possible, and prefer to use clip and grow to shape them.

79.8 Additional Information

79.8.1 Natural History

The European species typically grows on limestone chalk soils as an understory shrub in beech forests, or as scrub in dry Mediterranean hill country.

Japanese boxwoods are found in Japan and Taiwan, but only in cultivation. The original source in the wild has never been identified.

79.8.1.1 Cultivation

In the landscape, European boxwoods can get very large (5 ft. wide, 15 ft. tall), and are long-lived in good conditions. Japanese boxwoods are smaller than the European species, usually not growing more than 4 feet tall and wide, though larger specimens have been seen.

‘Kingsville Dwarf’ is a cultivar of Japanese boxwood that has extremely small leaves. This cultivar also is very slow growing compared to other Japanese and European cultivars, but in my hands has been very hardy. Growers say that ‘Kingsville’ occasionally has fast-growing full size shoots, though In 10 years of growing this cultivar, I have not seen this happen. These are revertant shoots where the dwarfing mutation has disappeared. The shoots will grow faster and drain energy from the dwarf portions. They should be removed immediately.

In my hands, European boxwoods in pots have been less tolerant of both heat and cold than Japanese boxwoods.