Bonsai are traditionally grown out-of-doors, and are brought inside only for display. Though your juniper bonsai will tolerate full sun, you may find yourself having to water daily. The ideal circumstance which would give it sufficient sunlight, while reducing the need to water often, would be morning sun with afternoon shade. Light shade all day long would be O.K. too.
Tradition aside, an indoor placement would be fine, so long as the tree recieves at least two hours of direct sunlight per day. Do not set it where air from an air conditioner or heat vent blows on it.
Water when the soil looks and feels dry on the surface. Under most conditions this will occur every two or three days. After a while you will be able to tell by "heft" when watering is needed.
To water, set the pot in water almost rim deep, for 1/2 to 1 hour, saturating the soil through the holes in the bottom. Don't leave your bonsai standing in the water all the time, that would cause root rot.
A proper cycle of watering will cause the soil to vary from a good soaking to being somewhat dry.
As with any potted plant, don't use water that has been through a water softener. In areas where there is a high concentration of minerals in the water, leach the soil by occasionally flushing it with distilled water.
Spider mites are the natural enemy of all junipers, and are especially bad indoors. Spray at least once a month with any insecticide intended for your household plants. "Shultz's Household Plant Spray" is widely available and works well. Also, be sure to spray other nearby plants which may be harbouring mites.
An element of keeping your bonsai as a miniature tree is to allow it only enough plant food to stay healthy, without rapid growth. Watering it with a half-strength solution of fertilizer once every six weeks or so, during the Spring and early Summer will be enough. We use "Miracle Grow" on our personal bonsai.
In the Spring, and possibly again in the Fall, buds will form on the branch tips. If these buds aren't removed by pinching, fast growing limbs will develop, resulting in a ragged appearance. Don't be shy about pinching off new growth; the bonsai's appearance is dependent on your personal input, and as with any art form, becomes a personal expression of it's owner.
Every other Spring, your bonsai will need to have it's roots pruned, to prevent it from becoming too root bound. Take the tree from it's pot, and carefully remove some of the soil from around the rootball. Trim off 1/3 of the roots, all the way around. Return the plant to it's pot, using a mixture of household potting soil with 1/3 part sand added, to replace the lost soil. Soak it in a solution of vitamin b-1 transplant shock supplement, and mist with water a couple of times a day for two weeks.
Your juniper bonsai does best if it has a "Winter" to complete it's natural cycle. Place it in a cool room during the Winter, the cooler the better. Freezing will not hurt it, so long as it isn't subjected to a rapid rise in temperature. If it is cool enough (50 degrees F or less) indirect light will be sufficient. Watering requirements will be much reduced.
If you can't simulate Winter, and must keep the bonsai in your living area, be sure to place it where it will receive the minimum sunlight requirement. Whenever your bonsai is kept indoors at room temperature, be sure to humidify it by misting it a couple of times a day. Spraying for mites also becomes more important.
Taken from "Juniper Bonsai Care Instructions", a pamphlet provided with the purchase of the Juniper Bonsai.
It's a Fact: The juniper bonsai is one of the hardier species of bonsai trees, and is easy to start with for beginners!
Another fact: This node put me at level three. Yay!