Pruning Nandina (Heavenly Bamboo)

Nandinas (‌Nandina domestica‌) are tough, durable evergreen shrubs native to Japan that produce clusters of small pink or white flowers in the spring followed by red berries. These plants belong to the barberry family (Berberidaceae). However, nandina's common name is heavenly bamboo since the erect, canelike stems and compound leaves look like bamboo. Easy to care for, tolerant of adverse environmental conditions and resistant to disease, nandina is often used as an evergreen landscape shrub in USDA plant hardiness zones 8 through 10, providing colorful foliage in an attractive fall color display, and as a deciduous plant in the colder zones of 6 and 7.

Although this shrub grows lustily without maintenance or trimming, pruning nandina on an annual basis can keep it compact and prevent taller shrubs from getting leggy. If you are ready to prune your nandina, a few simple gardening tips will put you on the best path.

To prune or not to prune? That is the question with nandina. Drought-tolerant, tough, and independent, nandinas are broadleaf evergreen shrubs that stay healthy year-round without much human intervention. They are especially prolific in the Southeastern United States — think Florida and the Carolinas — where large specimens have been growing for over a century without any pruning care. But an annual pruning to remove dead wood is usually a good idea. This should occur in late winter.

1. Use a sharp, clean pruner to remove all dead branches.
2. Take out any damaged or diseased wood, making the cuts several inches into healthy wood just above leaf nodes.
3. Prune branches or canes that can rub off the bark and leave wounds. Direct the new growth outward rather than inward by making the cut just above an outward-facing bud.

Heavenly bamboo sometimes grows too tall for its space. Although compact cultivars (dwarf nandina) are available and rarely need trimming, taller specimen plants grow to 8 feet tall. They can begin to look leggy over time, especially if they are not given full-sun locations. If this happens to your plant, prune in late winter or early spring. This is also the time to prune for size.

Pruning Out Nandina Canes to Create a Fuller Plant

The nandina plant looks like bamboo with its lightly branched, canelike stems. If the shrub has become lanky with limited growth at the bottom, remove one-third of these stems. Make each cut at ground level and select the older canes for the pruning. The resulting new growth will fill out the plant during the growing season and increase the number of new leaves. They grow in an attractive bluish-pink when young before turning to soft light green.

Prune out the top third of the canopy of your nandina if it is getting too tall. Prune out up to one-third of the width with shears if it is spreading beyond its site. Nandinas generally grow 5 to 8 feet tall with a spread of 3 to 5 feet, shooting up 12 to 24 inches per year. Ideally, it is placed where it can attain its full mature size, but if space is a problem, annual height pruning helps.

Heavenly bamboo, despite its angelic name, comes with some down-to-earth concerns. It is considered invasive in the Southeast and other areas of the U.S. And the berries of ‌Nandina domestica‌ contain cyanide and are toxic to humans as well as dogs, cats, horses, and some birds (such as cedar waxwings). If you're growing nandina in an area where it is potentially hazardous to the ecosystem, take special pruning steps to prevent invasive spread of the plant and minimize threats to wildlife.

Victoria Blackstone, expert gardener and horticulturist, lives in South Carolina where these shrubs are terribly invasive. Blackstone says "the invasive spread of nandina is twofold: by rhizomes and also by the fruit."

Nandina has strong underground rhizomatous roots that can move into adjacent lands and naturalize there, establishing dense stands in forest habitats or disturbing other sites by shading and choking out native vegetation. Preventing this type of spread is difficult, because even if you remove plants by the roots, new plants can sprout from a single root or rhizome fragment left behind. The most effective way to control the spread of invasive nandinas is by using a nonselective herbicide, such as glyphosate or triclopyr, to remove the plants and their root systems.

Nandina also spreads via the seeds contained in its berries.

"The berries not only prolifically self-sow, but they're also consumed and disseminated by wildlife all over the place," Blackstone tells Hunker.

If the berries are left to fall on the ground, the seeds within will self-sow and grow into new plants naturally. Berries and their seeds are also spread by birds and other animals consuming the berries and distributing the seeds through their waste.

Blackstone suggests removing the flowers before they set fruit to prevent the spread of nandina. But if you really don't want to nip the flowers, you can wait until the berries form and remove them while they're still green (before they're ripe and consumed by wildlife).

If you've allowed your nandina to grow unchecked for a number of years or if you've inherited a neglected nandina, consider pruning it back several years in a row to renew the shrub. This will also reduce the chance that it will slip those roots under the fence and set up camp in nearby woodlands.

To prune back a neglected nandina, cut down the oldest canes to ground level in late winter in year one. Take out about one-third of the stems. The second year, repeat this procedure, removing more stems and taking them back to ground level. The third year, give the stems that have not been cut the same treatment. The resulting plant will have stems of different heights, producing attractive new foliage.