Nandina, or Heavenly bamboo, is a deservedly popular landscape staple in the south. Few other shrubs are super-low maintenance, are sun and shade tolerant, have attractive feathery leaves that are a lovely bronze in spring and showy red for fall and winter, plus many varieties flower nicely and adorn themselves with brilliant red berries. They are by nature fairly slow growing and rarely outgrow their location. What’s not to love?
The only flaw, and a minor one at that, is that they can become overly thick with age, or develop an irregular shape. I say minor flaw because it is so darn easy to prune them properly, and late winter is the best time to prune Nandina in the Piedmont. There are several forms of Nandina that vary in size from about 2 feet to well over 6 feet, but the basic technique is the same. As far as frequency goes, dwarf or groundcover Nandinas may need little if any pruning, with perhaps only the occasional tall stem removed; taller varieties may begin to show bare stems that need removing yearly.
You'll need a good pair of pruners, or loppers for very old, thick canes. Remove the tallest, oldest canes, or any that lean or cause the overall shape to become irregular and awkward. In addition, if the clump is very thick and the foliage seems crowded, thin out by removing a few of the oldest or thickest canes. Prune the canes out all the way to the ground and don’t remove more than 1/3 of the total canes. This will encourage fresh, new stems to sprout with beautiful new foliage. Never shear Nandina as it destroys the soft, informal character of the plant.
In almost every instance you will remove all of the tall bare stems completely and not leave any visible after pruning. The exception would be an old clump of Nandina that has become very sparse with a lot of bare cane showing and little or no bottom growth. In this case you would remove one-third of the canes in the first year, starting with the tallest or the ones leaning the most. Then prune another third of the total canes the next year, and so on. Cutting the tall canes will encourage new growth to sprout from the base the following spring. In three years all of the oldest canes will have been removed, and new growth encouraged.
That’s it! Check out this video with Katie Cardille demonstrating how to prune a Nandina.