Boxwood is a category of evergreen shrubs with approximately 70 different species. Typically found in the rocky hills of Africa, Asia, Central America, and Europe, the Boxwood is small, making them ideal for bonsai. In the springtime, the Boxwood will display male flowers of beautiful yellow, surrounded by single, female flowers.
Although you have many choices for bonsai, the two that work best for bonsai are the Japanese Box (Buxus microphylla) and the Common Box (Buxus sempervirens). For both of these species, you would find leaves of glossy, dark green. The only real difference between these two species of Boxwood is size, with the Japanese Box being a slower growing and smaller version.
When growing Boxwood for bonsai, they tolerate both sun and shade quite well. Keep in mind that excessive direct sunlight can burn the leaves. Boxwood is a hardy tree but to prevent damage to top growth, it needs good protection from wind and frost. You might notice the leaves of your Boxwood bonsai turning a bronze color during the cold months but this is perfectly normal. When growing Boxwood indoors, make sure you keep it in an unheated room with good circulation, which will help eliminate the risk of fungal disease.
During the growing season, Boxwood needs to be fed about every two weeks. For pruning, when you see new growth, trim this back throughout the growing season to help shape the tree. Because Boxwood is naturally stiff with angular appearance, you might consider using a style that will help soften its look. Then about every two to three years, the Boxwood would need to be repotted, scheduling this around the time you see new leaf buds. For soil, a basic bonsai mix is fine.
The most beautiful style for Boxwood is the informal upright although some bonsai enthusiast will try other forms. You can propagate the Boxwood bonsai in the summer by using root semi-ripe cuttings and in late spring, air layering. While the Boxwood is very hardy, they are prone to red spider mites, specifically in the summer months.
In addition, a fungal disease known as Box Blight can seriously damage mature Boxwood. With this, the leaves would develop spots, which then lead to quick defoliation. Other symptoms include black streaks on the bark and a grey colored fungus on any remaining foliate. Unfortunately, the bonsai will usually die in about two to three months. Currently, the cause of Box Blight is unknown, as is a cure.