Indoor vs outdoor species

Most classic bonsai species, including junipers, maples, pines and other temperate trees, are outdoor trees that need a real seasonal cycle, including a cold dormant period in winter, to stay healthy long term. Keeping these species indoors year-round, even in a bright room, usually weakens them over a year or two because they never get the dormancy their biology expects.

A smaller group of tropical and subtropical species, such as ficus, jade and some elephant bushes, tolerate stable indoor temperatures and can be kept as houseplants shaped in bonsai style. Even these species still want as much light as possible, ideally near a bright window or under a grow light, since typical indoor light levels are far dimmer than an outdoor garden.

The most common beginner mistake in this area is buying an outdoor species, often a juniper, from a shop displaying it as a houseplant, then keeping it inside where it slowly declines. Confirming whether a specific species needs outdoor seasons or tolerates indoor life, before deciding where it will live, avoids this problem entirely.