Does a Bonsai Orange Tree Have to Stay Indoors?
Not all the time. Like all sweet oranges (Citrus sinensis), it’s a heat-loving tree suitable for USDA plant hardiness zones 9 through 11. If you live in a colder area, it still does best when kept outside in full sun (eight or more hours per day) from spring to fall.
A bonsai orange tree should remain indoors as long as the outdoor temperature is consistently below 55°F (12.8°C).
Expert gardener’s tip: Keep an indoor tree in a south-facing window or sunroom. It may need grow lights in winter, when sunlight is scarce.
How Often Should I Water It?
Water whenever the top 0.4 inches (1mm) of soil feels dry to the touch. Your bonsai tree needs a soil consisting of:
- 2 parts baked clay or kitty litter
- 1 part peat moss
- 1 part pumice
- 1 part lava rock
The clay or kitty litter and peat moss hold enough water to sustain the tree, while the excess drains rapidly through the pumice and lava rock. The tree won’t survive long in wet soil.
What About Fertilizer?
Fertilize your bonsai orange tree weekly from spring until fall and monthly during winter. Apply a liquid citrus fertilizer at half the manufacturer’s recommended dose. Diluting the dose keeps minerals salts from accumulating in the pot.
When Should I Prune and Wire?
Whenever a new shoot has sprouted four leaves, cut it back to two. This encourages the growth of more branches that you can wire to shape the tree the way you like.
Wire the trees whenever you like. Use anodized aluminum wire in 1mm, 1.5mm, 2.5mm and 4mm thicknesses. Wrap the thick branches in wet raffia fiber (available at garden stores) before wiring. It stops the wire from cutting the wood when you bend the branches to shape.
How Often Should I Repot the Tree?
Lift your tree from its pot in before is starts growing in early spring. If roots are encircling the rootball, it’s time to repot. Young trees may need repotting every other year; older ones can wait three to five years.
Expert gardener’s tip: Because you’ll trim its roots when repotting, moving the tree to a larger container may not be necessary.