Plant Care 101: Thuja Green Giants

Blair Brown — May 30, 2019

When we say Green Giant, we’re not referring to the Jolly Green Giant mascot associated with canned and frozen vegetables. We’re referring to the Thuja Green Giant. You can’t have ‘giant’ in the name of a plant that doesn’t get massive, so this tree lives up to its name.

Quickly growing to heights of 20 to 40 feet tall, the rapid growth of Thuja Green Giants makes them the perfect candidates for large Privacy Trees. However, Thujas are beautiful ornamental trees with a variety of uses.

What are Thuja Green Giants?

Thuja Green Giants are commonly known as arborvitaes, a word derived from Latin that means tree of life. They’re called trees of life because their sap can supposedly be used for medicinal purposes. This covers all varieties of Thujas, from the Nigra Thuja to the Emerald Green Giant.

The Thuja Green Giant is actually a cross between two different Thuja varieties: namely, the Standishii and Plicata varieties.

  • The Thuja Standishii is a Thuja variety that’s native to Japan and commonly gets 20 to 35 feet tall.
  • The Thuja Plicata is a variety native to North America that gets 65 to 70 feet tall.

When they come together to form Thuja Green Giants, they make a beautiful, fast-growing evergreen with a pyramidal shape. They also boast low-maintenance care, strong pest and disease resistance, and high level of cold hardiness.

Planting Thuja Green Giants

Facts on Thuja Green Giants

Thuja Green Giants are recommended for growing zones 5 through 9. They’re cold hardy down to about -20 degrees and can even put up with the snow since they boast strong, durable branches. Furthermore, if you line your driveway with Thujas, they’ll create a barrier that prevents snow from building up.

The thick emerald foliage on Thuja Green Giants creates a tough barrier against the wind as well. Cold, harsh winds can be damaging to smaller trees and shrubs. Cold blasts also hit homes and cause people’s heating bills to go up.

And if you need fast-growing Privacy Trees, then Thuja Green Giants are the way to go. Once you plant them, they’ll take off, growing between 3 and 5 feet a year. People love to plant them in order to create a living fence. Thujas may get quite large, up to 40 feet tall and 6 to 12 feet wide, but they respond very well to pruning for your desired height.

Best of all, the Thuja’s exterior light and feather foliage give it an attractive texture, while its interior dark green foliage with slight yellow hues make it pop. This conifer’s pyramidal shape is also very attractive to the eye.

Green Giant Arborvitae Care

  • How Much Sun Does a Thuja Green Giant Need?

    • Select a site that receives full to partial sunlight – they will grow more quickly in full sunlight. Six hours of direct sunlight a day will suffice.
  • Best Soil for a Thuja Green Giant

    • Thujas can adapt to a huge variety of different soil types, ranging from sandy to heavy with clay. Although they prefer slightly acidic soil, they adjust fine to soils that are alkaline and very acidic.
    • After planting your Thuja Green Giant, keep the soil moist but not soggy or oversaturated. Thujas won’t do well if they sit in standing water, so avoid low areas of your yard where standing water could collect.
  • Why is My Thuja Green Giant Turning Brown?

    • Thujas will turn brown due to a couple of reasons, most due to the environment in which they are living. These environmental causes include lack of water, sunlight and even freezing temperatures.
  • How Much Water Do Thuja Green Giants Need?

    • These arborvitaes get thirsty often. Water your Thujas three times a month during the summer months, and twice a month during the colder months. If you experience periods of drought or extreme heat, water your trees more often.
    • It’s easy to tell when Thujas aren’t getting enough water: their needle tips will start to turn brown or the foliage will look dull, yellowed and weak. Signs of overwatering include drooping branches and discoloration of the branches.
  • Best Mulch for a Thuja Green Giant

    • You can help your soil retain moisture by placing a 3-inch thick layer of mulch around the tree’s base. The mulch will also keep weeds away and regulate soil temperature. Mulch will keep your soil warm in the winter and cool in the summer.

Fertilizing Thuja Green Giants

Generally, Thuja Green Giants don’t need to be fertilized. But you can give your Thujas a boost once or twice a year with a well-balanced, slow release fertilizer, like formula 10-10-10 or 14-14-14. If you choose to fertilize your Thujas, do so in the early spring after the final frost of the season or in the early fall.

How to Prune a Thuja Green Giant

No pruning is required for Thuja Green Giants. They’ll quickly reach their massive heights if left untouched. You can promote wider growth that spreads out into a bushier formation by cutting back around a third of the tree’s central leader. With hand pruners or shears, you can cut and shape your Thujas as desired. You can even mold Thujas into hedges that are flat across the top, as long as their width is at least 6 inches.

Blair Brown

Blair is the Content Marketing Manager at, and though she's not your traditional gardener, the planting world is definitely growing on her (pun intended!). She's enjoyed digging into plant care and maintenance and growing her plant collection, especially with exotic indoor varieties.

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