Its botanic name Buxus comes from the Greek word puksos, meaning ‘dense’, because of its very hard wood, which is second only to ebony as the hardest wood of all. Because of this feature, craftsmen, lathe operators, cabinet makers, sculptors and artists have used it to create masterpieces. Eternity symbol for the Gauls, boxwood (known as box in the UK) soon became a holy plant in many religions. In horticulture, it is highly regarded for topiary works, but above all, Buxus is very suitable for creating amazing bonsai.
- Common name: Boxwood, the common box, or European box
- Genus: Buxus
- Higher taxon: Eudicots
- Species: Buxus sempervirens L
- Skill level: Advanced
- Soil type: It’s a plant that prefers chalky soil. In Italy, it thrives on sub-alpine mountain slopes, favouring broadleaf woods. Found in undergrowth of flatlands up to mountainous areas, bluffs and dry chalky screed.
- Flower and fruit: The flowers are small and yellowish and they are monoecious with distinct male and female flowers on the same plant. The fruit is a small capsule with numerous seeds
- Foliage: The leaves are opposite, from round to lanceolate, leathery, and in general rather small. The most diffuse species in Italy are Buxus sempervirens and Buxus balearica, which is native to Sardinia and has larger, lighter green leaves than the former type and scented flowers.
- Bark: The trunk has dense branching and the bark is a light brown, which changes to grey with age.
You can propagate by taking cuttings of at least 10cm in length from September-March. It’s best to take them when they are dark green and have slight ramification. Make an incision of at least 2cm. Use rooting vitamin B1 to speed up the rooting.
Air layering: It’s possible to achieve interesting material through this technique or to improve its root base. Best time to start is April.
Look for old hedges or search in mountainous regions. Best time to collect, is March or April.
It’s difficult to obtain quality material that is old and has developed a good thick trunk. Ask your bonsai nursery if they have any suitable material in stock.
Does not like frosty winds and frosts in general. Protect by sheltering in a cold frame. In the summer protect from hot sun. Semi shade is good spot for the tree.
To promote new shoots, remove leaves at the base of branches and leave only a few pairs of leaves at the tips. New shoots will emerge at the base of removed leaves.
Boxwood can be pruned after spring growth, which with stunning regularity produces 12 leaves on each shoot. No more, no less! Prune back to 2 leaves in April or May, depending on your climate. If you want to strengthen a branch, prune only when the colour of the new leaves matches the older ones. Take the opportunity of pruning to remove 3 year old yellowish leaves. As well as the aesthetic reasons, it also helps air and light to reach the centre of the crown.
Flower buds appear in July – easy to spot, being spherical and about 1.5 mm in diameter. It is best to remove them because they draw much of the tree’s energy, and also because at the leaves’ armpits where they grow, there will be no leaf buds the following year and no growth. If you realize a Buxus bonsai is producing too many flower buds, it could be caused by a nutrient deficiency. Try to add some trace elements.
How to promote back budding
When a Buxus is styled, foliage planes must be positioned flat like the shape of a hand. Do not try to give some volume to the pads, as is common with other species. If you leave a branch in a vertical position, only the apical buds will produce shoots. Flat pads will inhibit apical dominance. They will acquire volume later with back budding and increased ramification.
Sunlight will promote back budding at the ‘armpit’ of each leaf, sometimes even on the bare wood. Autumn budding is very unpredictable, unless the tree is styled in late summer. In that case, autumn budding can prove to be similar to a second spring.
The best time to repot is in early spring before growth commences. Buxus is tolerant to root pruning and will develop new roots easily. However, you can also repot during the dormant period (December-January) after you have pruned the foliage, but remember to protect it from the frost.
Repot every two years for younger trees, older trees every 3 to 4 years depending on the growth. Use a normal deciduous soil mix.
Any good draining chalky or alkaline soil will do. For optimum growth you need soil with a pH level of between 5.5 and 7.
Box prefers to have moist soil. Good drainage is important to allow it to grow healthily. In summer it needs plenty of water, don’t let it dry out. But don’t over water in winter.
This can be a problem because thick branches are rather brittle due to the absence of fibres in the wood, and therefore taking wire shaping less easily. Use immature branches that are still flexible and use aluminium wire.
Pests and diseases:
Box psyllids (psylla buxi): Sits on the tips of the leaves in spring and causes curling leafs and growth disturbance. Spray with insecticide at the end of winter to prevent infection.
Box mite (phytoptus canestrinii): Leaves acquire pale stripes or dots, which can be yellowish in colour. They will not harm the tree and can be tolerated. No amateur garden pesticides will have any effect.
Box with yellow leaves: When the box shows yellow leaf tips it is time to feed. It’s caused by a lack of fertiliser and chalk. Add chalk in November and fertilise in spring.