Indoor bonsai: which trees really work inside

An indoor bonsai on the windowsill is a lovely idea. But here is the honest truth first: most bonsai are outdoor trees. They need sun, fresh air and a cool winter. Only a few species from warm regions can cope with living indoors long-term, and even they need the right light and spot. This guide to indoor bonsai for beginners shows you which trees those are and how to avoid the typical mistakes.

Why most bonsai belong outside

Trees from temperate climates, such as juniper, maple or pine, need a winter rest: a period when it gets cool and darker and the tree takes a break. In a warm home it never gets that break. On top of that, even a bright window gives far less light than outdoors. These trees slowly weaken indoors, even if the label says "indoor bonsai".

Trees from tropical and subtropical regions don't know a cold winter. That makes them the right candidates for indoors.

Species that work indoors

• Ficus (for example ficus ginseng): The classic and the best choice for beginners. It is forgiving, copes relatively well with dry heating air and likes room temperature all year. More in the ficus ginseng profile.
• Jade plant: Stores water in its thick leaves, so it forgives the odd missed watering. In return it needs a lot of light, ideally a few hours of direct sun. More in the jade plant profile.
• Chinese elm, with conditions: It is tough and can be kept indoors, but it needs a very bright spot and is happier in a cool, bright room in winter than next to the radiator. It does best if it can spend the summer outside. More in the Chinese elm profile.
• Olive, only with caveats: Honestly, it isn't a true indoor tree. It needs full sun and a cool, bright winter. Kept in a warm living room all year, it becomes weak and prone to pests. It works better if it spends summer outside and only comes in when there is frost. More in the olive tree profile.

The bonsai finder quickly shows you which tree suits your home.

Light: the most important point

Light is almost always in short supply indoors. A spot that feels bright to you is often too dark for a tree.

• Window direction: In the northern hemisphere, south-facing windows give the most light, east and west medium, north the least. For ficus and jade plant, a south, west or east window is ideal.
• Distance: Put the tree right at the window, not in the middle of the room. Just a few steps away from the glass the light gets much weaker.
• Warning signs: Long, thin shoots with big gaps between the leaves show that the tree is searching for light.
• Grow light: In winter or in darker spots, an LED grow light helps. Hang it close above the tree, but not touching the leaves. With a timer, the tree gets around 12 hours of light a day.

By the way, extra humidity or fertiliser can't make up for missing light.

Heating air and humidity

In winter, the air in heated rooms is very dry, and many indoor trees come from more humid regions.

• Keep away from heaters: Don't put the tree directly above or next to a radiator, or in the draught of an air conditioner.
• Humidity tray: A shallow tray with gravel and water under the pot raises the humidity right around the tree. The pot itself shouldn't stand in the water.
• Humidifier or plant groups: A humidifier works best. Several plants placed together also keep the air a little more humid.
• Misting is nice but only works briefly and does not replace watering.

Temperature and winter

• Tropical species such as ficus like an even room temperature all year. Watch out for cold windowsills at night and icy draughts when you air the room.
• Olive and Chinese elm are grateful for a cooler but bright winter spot, such as a barely heated room or a bright stairwell.
• Water less in winter: The tree grows more slowly and uses less water. Still water by feel, not by schedule, and never let the root ball dry out completely.
• Summer holiday outside: Many indoor trees enjoy a summer on the balcony or patio. Get them used to the sun slowly, or the leaves can burn.

The most common indoor mistakes

1. An outdoor tree in the living room, usually a juniper with an "indoor" label.
2. Too little light, because the tree is used as decoration on a shelf or table.
3. Watering by calendar instead of by finger test. Check the soil and water when the top is dry.
4. A spot right by the radiator or in a draught.
5. Moving it around constantly. Every change of place can make the tree drop leaves.
6. Treating it like a normal houseplant. The small pot holds very little water, so a bonsai needs more attention.

One more thing: in Japan, the ficus ginseng's species is called gajumaru (ガジュマル). In Okinawa, people say that little tree spirits called kijimuna live in old gajumaru trees and bring good fortune, which is why it is considered a lucky tree. A nice thought for your first indoor bonsai.