Boxwoods are evergreen shrubs commonly used in hedges and edging. They can be made into attractive bonsai because they are evergreen, easy to maintain, and have interesting bark. Their soft foliage readily grows in any direction and quantity you desire.
Boxwoods grow at a slow rate and have fine-grained hardwood, which is prized for fine carving in China.
Buxus sempervirens (English boxwood) and Buxus microphylla (Japanese boxwood) are common species used in landscaping. Japanese boxwood has slightly stiffer leaves.
The "Little King" of bonsai is the Kingsville boxwood (Buxus microphylla compacta), a very slow-growing dwarf variety perfect for Shohin (small) bonsai.
Sourcing and Collecting
Both English boxwood and Japanese boxwood can be found at your local nursery. Kingsville boxwood is more likely to be available at select nurseries and bonsai nurseries.
When shopping at a nursery, take a chopstick to lightly dig around the tree’s base to check for a radial root spread and ensure there is no reverse taper below the nursery soil level. The most important aspect of any bonsai is showing the age of the tree through the beauty of the trunk. It is usually best to buy a larger-sized tree with a more developed trunk and branches. Height is less important than a nicely buttressed trunk base and taper.
If you keep your eyes open, you may find neighbors or businesses redoing their landscaping and removing boxwood hedges. Asking permission to dig up some is a great way to acquire mature bushes with good trunk diameters. Try to retain as many roots and as much original soil as possible. If the soil around the roots is lost during the collection process, use pure pumice for potting freshly dug trees, or coarse sand if pumice is unavailable. Some recommend equal parts of perlite and peat moss or coconut coir.
When collecting, cut off redundant branches and as much foliage as possible to compensate for root loss. Wait until the tree becomes healthy and leafs out before trimming further, then carve the stubs into a more natural taper.
Environment
Boxwood bonsai can be placed in full sun if adequate watering is provided; otherwise, keep them in partial shade or morning sun.
Japanese boxwood leaves may turn yellowish-brown during colder months if planted in full sun without adequate water. They will regain their chlorophyll and green color with the return of spring growth.
To winterize your boxwood, keep it indoors or bury the root ball outdoors to prevent freezing.
Styling
Boxwoods can be styled into many forms, but they look best when trimmed to resemble aged oaks. Boxwood is valued for its fine-grained, hard wood, making it suitable for carving jin and shari to enhance the illusion of age.
Fall is the best time for styling and wiring, but with care, wiring can be done at almost any time of the year when branches are still supple. Older branches may snap when bent but could respond to guy wires, which gradually bring them down. It may take several months for branches to lignify and set. Wire loosely to avoid flaking the bark and causing scars. Aim for a 60-degree angle in your wiring. Once a branch has set its form, you can control future growth directions by clipping.
Trimming and Pruning
For established branches, trim branchlets down to two leaves after four to five leaves have formed. To develop a branch, let it grow out until fall, then trim to the desired length.
The goal is to maintain a cloud-like form with your foliage, keeping branches clean of excess leaves to allow light into the interior and encourage back budding. Keep the bottoms of branches free of leaves, and remove old, curled, or yellowing leaves.
Work from the lower branches upward, covering the branches with a cloth as you go to keep them clean of snippets. Hold each branchlet by the end as you carefully snip it. Remove all leaves within one inch of the trunk.
With adequate fertilization, boxwoods will bud out from old wood, providing many future branch locations. Branch density can quickly get out of hand, but trimming too often will weaken the bonsai; spring and fall trimming should suffice. Thin out older, thicker branches in favor of finer, younger branches. Follow the bonsai mantra: “Coarse to Fine.” Keep the tree open enough that “birds could fly through it.”
Watering
Boxwoods in pots need consistent watering, especially in summer heat. How much and how often you water depends on your soil mix, sun/shade exposure, temperature, and wind. Check at least once daily throughout the year. Water when the soil surface feels dry.
In summer, water in the early evening to avoid wetting the foliage and preventing fungal problems. In winter, during freezing weather, water in the morning to allow the soil to dry before nighttime freezing. In extremely cold climates, bring boxwoods indoors.
Pot and Repotting
Boxwoods are evergreen, allowing for a wide variety of pot styles and colors. You may want to match or contrast the trunk’s coloring. A shallow pot can be used due to the vigorous nature of boxwood roots.
To create a more majestic appearance, use a wide pot with a larger soil surface area. The best time to transplant is every two to three years in the spring. Potting up can be done in early fall if root work is kept to a minimum.
Keep the root pad thin by cleaning out roots directly under the tree, encouraging radial growth around the trunk. Always ensure the trunk base is at or below the pot’s rim.
Propagation
Boxwoods are among the easiest trees to propagate from branch cuttings. Take cuttings in spring during the active growth period.
Take 4- to 6-inch-long cuttings using a very sharp knife, cutting on a slant. Dip the cuttings in rooting hormone, then plant them in a 50/50 mix of peat moss and perlite. Keep the mix moist but not overly wet.
Fertilizing
Take care not to over-fertilize boxwoods, as this can encourage large leaf size and overly long internodes. Once the new spring leaves have hardened, use any good low-NPK fertilizer every two weeks, preferably a time-release formula to maintain consistent nutrient levels in the soil.
Occasionally spray with a dilute solution of water-soluble fertilizer (e.g., Miracle-Gro) to keep foliage green. Use very dilute fertilizer applications during colder winter months.
Disease and Pest Management
Boxwoods are generally disease- and pest-free. Occasionally aim a sharp spray of water under each branch to keep them clean. Do this in the shade or early morning to prevent hard water spots.
To eliminate pests, remove ants near your trees using Amdro products. For light infestations, use insecticidal soap like Safer’s. For general pest and disease prevention, try BioAdvanced All-in-One Rose and Flower Care.
For persistent scale or spider mites, use Malathion. If fungal infections occur, apply a copper-based fungicide or lime sulfur, always following the label instructions.
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