How to Care for a Thuja Occidentalis Nigra


Thuja occidentalis 'Nigra,' also called Dark American Arborvitae, is a low-maintenance evergreen shrub that grows 15 to 30 feet tall and 5 to 10 feet wide. Thuja occidentalis is often grown for use as screens or hedges. The shrub grows in a pyramid shape with dark green leaves and the females produce cones. The Thuja occidentalis is native to eastern Canada and northeastern America, and it grows well in USDA Zones 3 through 7, so it's hardy down to about -35 degrees Fahrenheit.

Step 1

Plant in full sunlight in well-drained but moist, loamy, deep soil. Thuja occidentalis shrubs love moisture.

Step 2

Water your Thuja occidentalis once per week or more frequently during periods of drought or hot temperatures, especially when young. Mature, more established shrubs are more tolerant of dry conditions.

Step 3

Shear the shrub to shape it and maintain its size. Prune the shrub lightly in early spring to get rid of tips with winter damage. Use hedging shears to make straight cuts on the sides and top of the Thuja occidentalis in late June or early July.

Step 4

Protect the shrub against high winds, heavy snowfalls and ice. Plant your Thuja occidentalis in a protected area and cover it with blankets when an ice storm threatens. Remove heavy snow from the shrub to prevent branches from breaking.

Tips and Warnings

  • Watch for leaf miner, spider mites and bagworms. Keep an eye out for leaf blight and canker. Deer also love to feed on this shrub. Treat your Thuja occidentalis with an insecticide to get rid of pests or a fungicide to eliminate diseases.

Things You'll Need

  • Pruning shears or loppers
  • Hedging shears
  • Blankets
  • All-purpose fertilizer
  • Insecticide and fungicide (optional)


  • Monrovia: Dark American Arborvitae -- Thuja occidentalis 'Nigra'
  • Thuja occidentalis (Nigra American Arborvitae)

Who Can Help

  • UConn Plant Database: Thuja occidentalis
  • Pruning Shrubs - Both Deciduous and Evergreen
Keywords: grow Thuja occidentalis Nigra, Dark American Arborvitae care, Thuja occidentalis Nigra care

About this Author

Sarah Terry brings 10 years of experience writing novels, business-to-business newsletters, and a plethora of how-to articles. Terry has written articles and publications for a wide range of markets and subject matters, including Medicine & Health, Eli Financial, Dartnell Publications and Eli Journals.