Best place for Junipers is outside, year-round, in a bright sunlight area. They can be inside for short durations but no more than a few days. They are not house plants but miniature living trees that thrive best outdoors. In winter months, a cool/cold environment is just fine but if temperatures drop below 14°F(-10°C), the tree must be protected. Foliage may change to a purplish brown color during frosty periods (as a result of a frost protection mechanism) but will turn green again in the Spring.
The single most crucial factor for a tree's health is the watering regimen. Watering must never be neglected and should occur every 3-4 days (1-2 days if temperatures are really high & bonsai is receiving full sun). Add water when soil appears dry but NEVER allow the soil to become completely dry. Be careful not to water too much, as Juniper roots don't like soil wetness. Misting can be done regularly, especially after repotting because it benefits from air humidity.
Use normal organic fertilizer pellets or balls every month during the growing seasons of Spring & Summer. In the Fall & Winter, fertilizing should occur every other month.
Pruning, wiring & repotting are also essential to bonsai development. If you need assistance with these additional care techniques, please contact me.