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Green Giant Arborvitae

(Thuja plicata × standishii ‘Green Giant’)

Thuja x Green Giant

Green Giant Arborvitae is an outstanding, easy-care tree that is versatile and adaptable for multiple uses in the landscape. It was first sent from Denmark to the U.S. National Arboretum in 1965 and has been a favorite with landscapers and homeowners ever since. Green Giant is a hybrid between Thuja plicata (Western Red cedar) and Thuja standishii (Japanese Arborvitae) and has qualities that surpass both of its parents. It grows well in USDA hardiness zones 5 through 8, which is a large area that includes more southern states than the range of other varieties of Arborvitae. Because of this, Green Giant can withstand heat and humidity, making it an excellent choice for southern U.S. gardens. The growth rate of Green Giant Arborvitae is 3’ to 5’ a year, and it is virtually pest-free and more deer-resistant than most other Thuja varieties. Its year-round, dark green, feathery foliage makes a beautiful, dense border or windbreak, and it can be easily clipped into a hedge, grown as a specimen tree, or planted in a container.

How to Care for Green Giant Arborvitae

  When to Plant  

The best time to plant your Green Giant is in the late winter or early spring when the ground is workable, but when the tree is not actively growing. It needs the growing season to establish a good root system before the following winter, so it is best not to plant it in the fall.

Green Giant Tree Pot, ready to plant

  Where to Plant

Site the trees on your property where they will best fulfill your need for a windbreak, privacy hedge, sunscreen, or border. Wherever you plant them, they will have the following sun and soil requirements.

Where to plant green giant arborvitae
Green Giant grows best in full sun in well-draining soil

Arborvitae will grow fastest in full sun, but they will also grow in some partial shade as long as they receive six hours of full sun during the day. The more sun the better since they will tend to thin out in shadier locations.

Since Arborvitae have extensive root systems, they will need soil that is loose, well-draining, free of rocks, and rich in organic matter. The pH of the soil should be between 6.0 and 8.0. You can easily test the pH of your soil with a pH meter or send a sample of your soil to your local county extension agent.

  How Many to Plant

Once you have selected a site, you’ll need to know how many trees to buy. If you’re looking for a Green Giant hedge, it is best to order Green Giant InstantHedge that are ready-to-plant sections of appropriately spaced planted hedging that come in several heights. They create a beautiful, dense hedge as soon as they’re planted and require minimal maintenance.

Green Giant InstantHedge unit
Installed Green Giant InstantHedge

If you want a windbreak, screen, or border, the spacing between the Green Giant trees will determine how many you’ll need. This is important! If Arborvitaes are planted too close together, they won’t have enough space above ground to spread their branches or space below ground to develop wide, substantial root systems to anchor the trees. Shorter trees can be planted closer together, but taller trees need enough space to grow healthfully. Below is a spacing guide according to desired tree height, with the distance between trees measured between trunks or centers. If you’re planting your trees near a fence or building, space them at least 10’ away for adequate growing room. Allow at least 20’ between other trees or plantings to prevent competition for water and nutrients.

Desired Screen Height6-8’10-12’15’+
Spacing Distance3’4-6’7-10’

  How to Plant 

When your trees arrive, water them immediately, before planting.

For individual trees, dig a hole the depth of the pots or root balls and two to three times as wide. Tease the roots apart and place the trees in the holes with the top of the roots just below the soil surface. Backfill the holes with soil and tamp them down gently so that they are firmly set and there are no air pockets.

Planting Tree Pots or Gallon sizes – note the soil level is even with the root flare

You can plant them in multiple configurations: linear, staggered, or creative.

Linear – space the plants evenly in a straight line. Staggered – space the plants evenly but in a staggered line. Creative – vary the spacing and lines to create a more natural or artistic line.

For a standard InstantHedge, dig a trench 12” deep and at least 18” wide to the length desired.

3 InstantHedge units (10 linear feet) being planted in a trench. Yes, you plant the cardboard box which then decomposes!

For a MiniHedgeXL, dig the trench 10.5” deep and 18” wide.

3 MiniHedgeXL (8.75 linear feet) being lifted from their pots and planted in a trench.

Plant the hedge units end to end, as closely together as you can get them. Add a layer of mulch over the root zone (without letting it touch the trunks), and water it in thoroughly.

Watering

Drip irrigation is a great way to irrigate your hedge without wasting water.

While the trees are established during their first and second years on your property, they will need to be watered weekly. Arborvitae requires moist soil, but are not soggy. Water by hand or with a slow-drip system a few feet away from the trunk to soak the soil, but not directly on the roots to prevent root rot. A long, deep soaking is always better than a quick, shallow watering.

  Fertilizing

A slow-release granular fertilizer in early spring will fuel your hedge’s growth throughout the growing season.

As your Green Giant trees grow, they will need nourishment to keep them in tip-top shape. Fertilize them every spring with an all-purpose, slow-release, granular fertilizer with high nitrogen content, like 16-5-9 or 18-5-12. Follow the instructions and water it in thoroughly.

  Pruning

pruning
Pruning any type of Arborvitae hedge requires some forethought, as cutting into old wood should be avoided.

Green Giant Arborvitae is very fast growing — 3’ to 5’ per year when established. To keep them at the desired height, you can prune them every year to a shorter size with clean, sharp shears or electric hedge trimmers.

Arborvitae only produces new growth at the ends of the branches, not on the old, bare sections close to the trunk. To shape the trees, limit their width, and achieve overall good density, cut the branches back up to a third of their length before the flush of growth in the spring or summer. Cut back any rogue branches that extend beyond the rest of the growth to maintain an attractive shape.

If the trees are growing too tall, cut the tops back to no more than one-third of the trees’ height early in the year. This is called topping the trees. Choose a spot where the existing branches will hide the cut leader, and then the tallest of the top branches will grow to become the new leader.

Prune your hedges every year before new growth on the tops and sides to maintain their shape and to encourage the best density.

  Mulching

mulching arborvitae
A 2-3” layer of mulch over the hedge’s root zone helps regulate soil temperature and conserve moisture.

To retain moisture at the roots, spread 2” to 3” of mulch out to the dripline of the trees, making sure to keep it away from the base of the tree trunks. 

Growing Green Giant Arborvitae in Containers

Growing Green Giant Arborvitae in Containers
Green Giant can be grown in containers for years before needing to be replaced.

Green Giant Arborvitae can be successfully grown in containers as accents around a pool, patio, or front entrance.

Choose a large pot, 18” to 24” in diameter, or a half barrel for trees 6’ to 8’ high. Make sure there are holes in the bottom of the pot so that the water can drain. Water that collects in the pot can put your tree at risk for root rot.

Use a loose, well-draining potting mix in the container so that there will be room for root expansion and air circulation. Do not use soil from the garden or a commercial garden or tree soil. It is too dense and compacts too quickly in a container, and will choke the roots.

Water your Green Giant when it is dry an inch down from the top of the soil. Always water thoroughly so that it runs through the soil and out the drainage holes. In warm weather, you will need to water every few days, but in cold weather, you can water it every week or two.

Since it is growing in a pot, your tree will need more frequent fertilization than if it is growing in the ground. You can use an all-purpose liquid fertilizer with a high nitrogen content every two weeks during the growing season. As an alternative, you can sprinkle granular all-purpose fertilizer on top of the soil and water it thoroughly following the directions.

Prune your tree at the top in the spring to keep it at the right height and around the sides if it’s growing too wide, using clean, sharp shears. Cut Green Giant Arborvitae tree back to no more than one-third of its size to encourage healthy growth.