Heavenly bamboo

Identification and origin

Nandina domestica belongs to the barberry family, Berberidaceae. Despite its common name, it is not a true bamboo: it only borrows the look, with upright, unbranched stems that carry the foliage near their tips. It is native to central and southern China; it has become naturalized in Japan, Korea, the southeastern United States and elsewhere after being introduced as an ornamental.

It is an evergreen shrub that forms a clump and spreads slowly through underground stems called rhizomes. In cultivation it usually grows 3–8 ft tall and 2–5 ft wide; old plants can reach 10 ft. Young canes are red and turn brown with age. The leaves are divided two or three times and measure 12 in – 2 ft long; their smooth, leathery leaflets emerge tinged red or bronze in spring, turn blue-green in summer, then purplish red in fall and winter, especially in sun. That color is still variable.

In late spring or early summer, upright panicles 10–12 in long carry small white flowers with yellow anthers, opening from pinkish buds. They are followed by round, bright red berries about 0 in across that stay on the plant all winter and into early spring. Fruiting is heavier when several plants are grouped together.

Light

Heavenly bamboo grows in anything from full sun to heavy shade. Sun brings out the strongest fall and winter color; in shade the foliage stays greener. Choose a spot sheltered from cold, drying winds, which damage the evergreen foliage.

It is not a houseplant: grow it in the garden or in a large container on a patio or balcony.

Watering

Once established, heavenly bamboo tolerates drought and needs little water. It still grows best in moist, well-drained soil: after planting and through the first seasons, keep the soil moist without making it soggy, and keep an eye on the foliage during dry summers. It also tolerates wet soils.

In a container, the volume of soil is small: check the moisture of the mix more often than in the garden. An organic mulch at least 3 in deep keeps the soil cool, suppresses weeds and supplies micronutrients as it breaks down.

Potting mix

It adapts to almost any soil: clay, loam, sand or soil rich in organic matter, whether acidic, neutral or alkaline. It also tolerates compacted soil, wind and moderate salinity. Even so, it prefers a rich, slightly acidic, well-drained soil. In strongly alkaline soil the foliage can turn yellow from chlorosis; iron sulfate or iron chelate corrects it.

As for feeding, a complete slow-release fertilizer, applied lightly three or four times a year, is enough. There is no need to push it: this shrub is not a heavy feeder, and the organic mulch adds to what you apply.

Temperature

Heavenly bamboo is hardy in USDA zones 6a to 9b. It withstands most cold winters; in zone 6, however, the stems can be damaged at around -0 °F and below.

Its foliage is evergreen to semi-evergreen: in hard winters it can lose part of it. A site sheltered from cold winds limits the damage.

Repotting

Heavenly bamboo transplants easily from a container; after planting, mulch around the base with bark. Its clumping habit and moderate growth suit containers and narrow spaces, and a well-kept planting can thrive for decades. For containers, borders and foundation plantings, choose compact, low-fruiting cultivars such as ‘Harbour Dwarf’, ‘Firepower’ or ‘Wood’s Dwarf’. When the clump grows too wide for its container, that is the time to remove suckers and propagate it.

Pruning

The canes do not branch: cutting a tip does not produce side shoots. To keep a dense clump, remove about a third of the canes at ground level each spring, starting with the oldest, thickest and weakest ones. New shoots then come up from the rhizomes. To rejuvenate a leggy plant, cut all the canes at different heights just above a node before growth starts, or cut only some of them one year and the rest the following year.

Compact, slow-growing cultivars hardly need pruning; a light trim in spring is enough. To keep the seeds from spreading, cut off the flower or fruit clusters.

Propagation

• Seed: the most common method. Collect ripe seed in fall and store it dry and cold, at about 39 °F, while the still-immature embryo develops. Sow it the following summer: germination takes about two months and the seedlings grow slowly.
• Division and suckers: remove the suckers that form at the base of old plants, with their roots, and replant them right away.
• Cuttings: harder; semi-hardwood cuttings root better with a rooting hormone.
• Tissue culture: it has also been successful.

For a new clump in a hurry, suckers remain the simplest option.

Common problems

• Invasiveness: in the southeastern United States, birds carry the seeds far from gardens and heavenly bamboo forms dense thickets in natural areas. Where it is listed as invasive, choose cultivars that set little or no fruit, such as ‘Firepower’ or ‘Harbour Dwarf’, or remove the fruit.
• Yellow leaves: chlorosis in strongly alkaline soil.
• Cupped, twisted leaves and stunted growth: a nonlethal virus that ‘Atropurpurea Nana’, ‘Firepower’ and ‘Harbour Dwarf’ can carry.
• Scale insects: cottony cushion scale can settle on the canes.
• Honey fungus: a rare root disease.
• Clump bare at the base: lack of renewal pruning.

On the whole, heavenly bamboo has few pest and disease problems, and deer leave it alone. A symptom can have several causes: check the soil, the exposure and any recent cold before drawing conclusions.

Toxicity

All parts of the plant contain cyanogenic glycosides, which release cyanide when the plant is chewed or damaged. It is toxic to dogs, cats, horses, livestock, birds and people. In animals, eating it can cause vomiting, drooling, weakness, incoordination, breathing difficulty and seizures; death is rare in pets. Cedar waxwings have died after eating large numbers of the berries. Wear gloves when handling it, keep it away from children and animals, and call a veterinarian or a poison control center if any is eaten.