Bonsai care: indoor ficus and outdoor juniper

Light

Light is the first limit for any tree in a pot this small. The RHS says indoor bonsai need lots of light, and Clemson grows weeping figs in bright, indirect or curtain-filtered sun, adding that they handle some direct sun if the humidity is high. NC State rates Ficus microcarpa for full sun to part shade. On the Illinois Extension scale, aim for bright light, about 300 foot-candles, right at an east or west window, or a spot within a few feet of a south window, where direct sun reaches 1,500 foot-candles.

Pick the spot and keep it. NC State warns that Ficus benjamina is very sensitive to light, so a moved tree may drop its leaves and grow new ones adapted to the new light. Junipers are a different case entirely: NC State lists Juniperus procumbens 'Nana' for full sun, six or more hours of direct sunlight a day, which no indoor window reliably gives.

Water

A bonsai holds so little compost that watering is a daily check, not a weekly chore. The RHS explains that the small, shallow containers restrict both water and nutrients and that the compost dries quickly in warm, windy weather. Its rule is simple: water as and when needed, aiming to keep the compost just moist. Outdoors in summer, the RHS says, that can mean once or twice a day.

Water gently and completely. The RHS recommends a fine rose so water soaks in rather than running off the surface, and rainwater where possible, because it reduces the buildup of minerals in the compost. Keep watering until it flows from the drainage holes, then let the pot drain fully. Clemson adds for weeping figs that the tree should never be waterlogged or left with water in its saucer.

Indoor ficus slow down in winter, and Clemson allows the soil to dry slightly between waterings then. Outdoor junipers resting through the cold still lose water, and the RHS cautions that a dry week in winter can catch you out, so keep checking the pot right through the season.

Soil and pH

Bonsai compost has to drain in seconds yet hold enough moisture for a day. The RHS gives a home recipe: two parts by volume of peat-free potting compost, two parts horticultural sharp sand or lime-free alpine grit, and one part peat-free John Innes No 3, swapping in ericaceous compost for lime-hating species. A controlled-release fertilizer can go into the mix at the manufacturer's rate. Specialized bonsai mixes do the same job. Ordinary houseplant compost alone stays too wet in a shallow tray. Junipers are even less forgiving of wet roots: Missouri Botanical Garden calls Juniperus procumbens intolerant of wet soils and partial to a dryish, sandy one.

Humidity

Tropical bonsai want moist air. The RHS lists humidity alongside light and constant temperature as the needs of indoor bonsai, Clemson says weeping figs prefer high humidity, and NC State calls 70 to 100 percent preferable for Ficus microcarpa, noting that it favors aerial roots. Few homes come close in winter, so set the tray on a wide saucer of wet pebbles, keep the pot clear of the water, and run a humidifier nearby if the heating is on.

Temperature

Clemson's ideal for weeping figs is 65 to 70°F at night and 75 to 85°F by day, and NC State says Ficus microcarpa suits temperatures above 68°F all year long. NC State also calls Ficus benjamina intolerant of cold and very frost sensitive. Keep a ficus bonsai away from cold glass, outside doors and heat vents; Clemson warns that drafts and vents trigger heavy leaf drop. A summer outdoors in morning sun and afternoon shade suits it, as long as it comes back inside before nights turn cool.

Fertilizer

A small pot runs out of food quickly, but too much feeding produces soft growth. The RHS suggests a slow-release balanced fertilizer at repotting and, once that is spent, a balanced liquid feed at the low dose on the label every two weeks during the growing season, warning that overfeeding gives excessive growth prone to pests and disease. Clemson's schedule for a healthy weeping fig is a liquid fertilizer every month or two in the growing season. Stop in winter.

Work out the dose for your watering can with the fertilizer dilution calculator →

Repotting

Repotting a bonsai means root pruning, not moving up a size. The RHS says to do it every two to three years, more often for fast growers and every three to five for slow pines, in spring before new growth resumes. Lift the tree out, comb away the old compost, cut back long roots to leave a flat, circular root ball, and return it to the same container with fresh mix worked in around the roots with a chopstick. Water well and keep it in a sheltered, shady spot until it recovers. Clemson notes that a weeping fig tolerates being slightly root bound.

• Roots fill the container and water runs off instead of soaking in
• New leaves come in small and growth slows, Clemson's signs of a crowded weeping fig
• Two or three years have passed since the last root pruning

Propagation

Ficus is the easy one to multiply. NC State says Ficus microcarpa roots readily from cuttings, either in water or straight into sand or potting soil, and Clemson notes that weeping figs root best from cuttings taken in summer and can be air layered at any season. Air layering is the bonsai grower's shortcut: a thick branch rooted while still on the tree becomes a ready-made trunk. Expect years of pruning before a rooted cutting looks like a bonsai.

Methods: Stem cuttings (ficus), Air layering (ficus) · Best season: summer for cuttings; air layering at any season.

Common problems

With ficus, the signature complaint is leaf drop. Clemson writes that weeping figs react to almost any stress by shedding leaves, listing overwatering, underwatering, drafts, lack of nitrogen and low light, and that they often drop leaves after a move or repotting before settling. The RHS names vine weevil, scale insects, slugs and powdery mildew as common bonsai problems, and Clemson adds spider mites and scale as frequent ficus pests. A juniper browning indoors is not a pest problem at all; it is in the wrong place.

Not sure which one it is? Try the plant problem diagnosis tool →

Is the bonsai toxic to cats and dogs?

The ASPCA lists ficus as toxic to cats, dogs and horses: its weeping fig and fig entries give a proteolytic enzyme, ficin, and psoralen, ficusin, as the toxic principles, with gastrointestinal and dermal irritation as the signs. Silver jade, another indoor bonsai the RHS names, is also toxic, with nausea and retching. We found no ASPCA entry for juniper in its cat or dog plant lists, so its risk is unrated rather than proven safe. Keep bonsai out of a pet's reach, and call your veterinarian or the ASPCA Animal Poison Control Center if one chews the tree.

Check any other plant against the ASPCA lists →