Chinese Juniper - Juniperus Chinensis
Pruning: To develop the foliage pads, long shoots which stick out of the silhouette can be pinched or cut at the base with sharp scissors throughout the growth season. Do not trim the juniper like a hedge because the removal of all growing tips will weaken the tree and the cut will turn the needles brown. When the foliage pads become too dense they must be thinned out with sharp scissors at the base. The Juniper Bonsai is generally a strong tree that also withstands aggressive pruning quite well. But it cannot bud again from bare tree parts, so take care that there is some foliage left on every branch you want to keep alive. Continue reading about pruning Bonsai trees.
Place the tree outside, year-round, on a bright spot with lots of sunlight. The Juniper cannot live indoors. During the winter protect the tree once temperatures drop below -10 degrees C (14F). Some species change their foliage color during frosty periods to a purplish brown which is connected with their frost protection mechanism. In spring they will turn green again.
Use normal organic fertilizer pellets or balls every month during the growth season or a liquid fertilizer each week. If strong growth is desired some higher nitrogen levels can be applied in spring.
Wiring: Junipers which are produced for Bonsai purposes are already wired quite heavily in most cases when they are still very young. Dramatically twisted shapes are very popular and correspond with the natural shapes that used to grow in the Japanese mountains in former times. Junipers can be strongly bent, if necessary wrapped with raffia or tape as a protection, but you must be careful with parts which possess deadwood. Those parts break easily. If they are large and old, you can split the deadwood off in order to bend the more flexible living parts. The foliage pads should be wired and fanned out after thinning when necessary, to let light and air get in. Otherwise the inner parts of the foliage pads will die. In addition to this, the danger of pest infestation is increased if the pads are too dense. From the aesthetic point of view we also want to achieve unobstructed structures and want to prevent the juniper from looking like broccoli.
Be careful not to water too much, as the juniper roots don't like soil wetness. Before you water, the soil should dry slightly. Misting the tree can be done regularly, especially after the tree has been repotted because it benefits from air humidity. Continue reading about watering Bonsai trees.
Repot the Juniper Bonsai tree once every two years, very old trees at longer intervals, using a basic (or somewhat more draining) soil mixture. Don't prune the roots too aggressively.
Pests / diseases: If junipers are well cared for and placed in an ideal position they are quite resistant against pests. It is important though not to let the foliage pads get too dense, because otherwise pests can settle in them more easily. During winter the junipers must be kept in a place with enough light and they must be checked for pests regularly because pests can even occur in winter. Junipers can sometimes get infested with spider mites, juniper scale, juniper aphids and juniper needle miners as well as juniper webworms for example. Customary insecticide / miticide sprays will help but you should also find the reason why the tree was prone to infestation. A big problem are fungal rust diseases. The diverse juniper species and cultivars have a very different level susceptibility to rust fungus, there are also some which are regarded as resistant. As a rule of thumb, the blue-green junipers are more resistant than those with yellowish-green foliage. The Japanese junipers are also not infested very often. In the internet you can find files which list many juniper species and cultivars and their susceptibility / resistance level to rust fungus. The rust fungus infests the junipers permanently and causes swellings from which hard, brown galls emerge. In spring, during rainy weather, the galls produce large, orange, gelatin-like tendrils, full of spores, which infest the leaves of pear trees (but there are also types of rust fungus which use hawthorn or crabapples as a second host instead of the pear). The fungus causes orange spots on the pear leaves. In late summer brownish proliferations grow from the bottom-sides of the leaves which release spores that infest junipers again. While the pear trees in most cases are not fatally affected – they are newly infested each year again and they can even be treated successfully with a fungicide, an infested juniper normally cannot be cured. The visibly infested branches die in most cases and the fungus can emerge on other tree parts. Removing the parts with the swellings and galls is no guarantee at all that the fungus will not reappear. Although some people have a different opinion, it is best to immediately burn up a rust-infested juniper or put it into the garbage instead of your compost heap.
Use seeds or cuttings.
One note of caution: box leaves are poisonous, and eating even a few can kill a small pet. As such, be sure to always keep this bonsai out of a child’s or animal’s reach.