One of the most loved species of cultivated Bonsai, the Juniper originates from China. Its compact foliage makes it one of the best candidates to become a Bonsai. Junipers grow slowly and are very long-lived. Junipers have a low, spread that makes them ideal for cascade and semi-cascade styles. One of the best characteristics of Juniper Bonsai is its hard resinous wood, ideal for advanced sculptural techniques such as jin, shari and sabamiki.
Green Mound Junipers are considered outdoor trees. They require a great deal of direct sunlight, changes in temperature, and humidity. If you keep them inside, find a place that gets tons of sun and consider getting a grow light. When kept outside it can tolerate just about any condition, but don’t let it freeze and make sure it gets afternoon shade in the summer.
Bonsai trees live in small pots and their world dries out much quicker than plants in the ground or in bigger pots, so close attention should be paid to watering. Check and water your bonsai every day. Striking a balance between not enough water and too much water can be a bit tricky but is very important. Water thoroughly and deeply when it needs water and let it catch its breath before watering again. An old bonsai watering trick is to place the entire pot in a sink of water an inch or two deep and let the water absorb from the holes in the bottom of the pot. Another favorite way to know if it needs watering is to lift it. You can get a sense for whether it needs watering by its weight. An inexpensive moisture meter takes the guesswork out of watering. We sell them. Water slowly so it absorbs into the dirt, otherwise the water will run all over your table. We pot our bonsai trees specifically to drain well, so it’s almost impossible to over water.
Leaves want humidity to keep them green and healthy. Any time your tree is inside, the air is very dry. Mist often during the day. Avoid putting your Bonsai near a draft or vent, which dries out the foliage. A humidity tray is a great way to increase humidity. These shallow trays filled with small stones have water in the bottom of the tray. Make sure the water does not reach the bottom of the Bonsai pot. As the water evaporates, it creates a moister environment.
Fertilizing a bonsai is essential to its health because the nutrients in the soil leave very quickly with the water. When new growth appears in the spring, it’s time to start feeding your bonsai. Use a balanced fertilizer with nitrogen during the growing season. In late summer when growth starts to slow, reduce the feeding to once a month. During the fall and winter months when your bonsai is in its ‘resting” or dormancy phase, use a no-nitrogen fertilizer. This will help the plant’s root system stay healthy and active without encouraging new foliage growth. A vitamin supplement/root stimulant is an excellent compliment to fertilizers.
The fertilizer we use is called SUPERthrive.
To develop the foliage, pinch out the tender new shoots using your fingers. Do not use scissors, as the cut needles will turn brown. Pinching must be done continuously during the growing season. Prune undesirable branches (especially those growing straight down from their parent branch) when repotting or during the growing season.
Use the thinnest training wire that will hold the branch in the desired position. DO NOT WIRE A BONSAI JUST AFTER REPOTTING. Wind the training wire in the direction the branch is bent in order to keep the wire from loosening. Wrapping the wire too tightly will cause scarring. Begin at the base of the Bonsai tree and slowly wrap the wire around the trunk to anchor. Continue along the branch you wish to train. Repeat the process as needed. After about 6 weeks, the branch should be able to maintain the shape on it’s own, and the wire can be removed. Cut the wire carefully from the branch. DO NOT UNWIND WIRES. This could cause the branch to break. Wiring is best done in autumn or early winter, so that the branches can become accustomed to their new position while the tree is dormant. Wiring done at other times must be watched carefully for signs of wire cutting into the bark, and must be removed immediately if this happens. If necessary, the tree can be re-wired after removing the old wire.
Reduce the roots gradually, removing no more than one third of the roots at each repotting. Repot young trees (up to 10 years) every other year. Repot older trees every 3-4 years. Repotting is best done in spring. Junipers can also be repotted in autumn if necessary, since they enter a period of renewed root growth at that time. Extensive root pruning in autumn is probably not a good idea, however. The tree should be protected from wind and direct sun for a month or two after repotting.
INSECTS & DISEASES:
Spider mites love Junipers. It’s hard to know that they have arrived because they are tiny little things, so spray for them whether you see them or not. You can spot spider mite trouble by the discoloration of foliage, usually gray and usually at the tips. But to know for use, place a clean sheet of white paper under the branches of your bonsai and gently tap the foliage. Tiny specks will fall onto the paper. Watch the specks carefully for a moment and see if any of them get up and try to leave. A moving speck is a spider mite. Use a mild insecticide that lists spider mites. It usually will take a few applications of insecticide to get the job done. Spider mites rarely do significant damage.
Junipers are also susceptible to fungus problems, especially in shadier, darker and cooler spots. Like spider mites, discoloration of the foliage is what you will see but this time it will be black or a pale lavender/grayish color. You can prevent fungal problems by keeping your bonsai in a well-ventilated area. Air circulation also encourages cell growth. Fungus problems are more likely during the dreary, wet fall and winter days and into the soggy spring days too. Use a mild fungicide and keep the air flowing to chase away fungal problems.