Thuja Green Giant tree has become one of the most popular trees for creating a living screen. It’s no wonder: Green Giant is an evergreen plant throughout the year; it is adaptable to most soil types; it is tolerant of light shade and of moderate drought; and it grows extremely fast.
I. Appearance and Characteristics
Thuja ( THEW-jə) is a genus of coniferous tree or shrub in the Cupressaceae (cypress family). There are five species in the genus, two native to North America and three native to eastern Asia. The genus is monophyletic and sister to Thujopsis. Members are commonly known as arborvitaes (from the Latin term for ‘tree of life’), thujas or cedars.
Thuja are evergreen trees growing from 10 to 200 feet (3 to 61 meters) tall, with stringy-textured reddish-brown bark. The shoots are flat, with side shoots only in a single plane. The leaves are scale-like and 1 to 10 mm (0.039 to 0.394 in) long, except young seedlings in their first year, which have needle-like leaves. The scale leaves are arranged in alternating decussate pairs in four rows along the twigs. The male cones are small, inconspicuous, and are located at the tips of the twigs. The female cones start out similarly inconspicuous, but grow to about 1 to 2 cm (0.39 to 0.79 in) long at maturity when 6–8 months old; they have 6-12 overlapping, thin, leathery scales, each scale bearing 1–2 small seeds with a pair of narrow lateral wings.
The five species in the genus Thuja are small to large evergreen trees with flattened branchlets. The leaves are arranged in flattened fan shaped groupings with resin-glands, and oppositely grouped in 4 ranks. The mature leaves are different from younger leaves, with those on larger branchlets having sharp, erect, free apices. The leaves on flattened lateral branchlets are crowded into oppressed groups and scale-like and the lateral pairs are keeled. With the exception of T. plicata, the lateral leaves are shorter than the facial leaves (Li et al. 2005). The solitary flowers are produced terminally. Pollen cones with 2-6 pairs of 2-4 pollen sacked sporophylls. Seed cones are ellipsoid, typically 9 to 14 mm (0.35 to 0.55 in) long, and mature and open the first year. The thin woody cone scales number from 4-6 pairs and are persistent and overlapping, with an oblong shape, they are also basifixed. The central 2-3 pairs of cone scales are fertile. The seed cones produce 1 to 3 seeds per scale, the seeds are lenticular in shape and equally 2 winged. Seedlings produce 2 cotyledons.
A hybrid between T. standishi and T. plicata has been named as the cultivar Thuja ‘Green Giant’.
Another very distinct and only distantly related species, formerly treated as Thuja orientalis, is now treated in a genus of its own, as Platycladus orientalis. The closest relatives of Thuja are Thujopsis dolabrata, distinct in its thicker foliage and stouter cones, and Tetraclinis articulata (Ancient Greek θυία or θύα, formerly classed in the genus and after which Thuja is named), distinct in its quadrangular foliage (not flattened) and cones with four thick, woody scales.
The genus Thuja, like many other forms of conifers, is represented by ancestral forms in Cretaceous rocks of northern Europe, and with the advance of time is found to migrate from northerly to more southerly regions, until during the Pliocene period, when it disappeared from Europe. Thuja is also known in the Miocene beds of the Dakotas.
II. How to Grow and Care
Sunlight
Photo by David J. Stang
CC BY-SA 4.0
“Green Giant” Arborvitae prefers full sun. It will tolerate part shade and actually thrives in some light afternoon shade in hot summer climates.
Watering
For the first two weeks, water your new tree every other day by holding a hose around it and counting to 20. If you don’t have a hose, 2 large watering cans full of water will do (smaller trees may only need a light soaking so a single can may suffice).
During the second two weeks, switch to watering every three days with the same method mentioned above. After the first month, water once a week unless it is dry and hot (no rain and temperatures above 80 degrees). If it is hot and dry, water twice a week. After the first six months, the trees will be established and won’t need any extra water. Your natural rainfall should be sufficient at this stage.
Soil
Able to grow in a range of soils such as poor soil and clay, it does best in moist, fertile, well-drained loans. Avoid wet soil that does not drain well and exposure to spray or salt.5
Fertilizing
For optimal growth feed your Thuja ‘Green Giant’ with a balanced evergreen tree and shrub fertilizer starting in the spring.
Photo by David J. Stang
CC BY-SA 4.0
Planting Instructions
This is a large landscape tree and as such, requires a bit of planning before planting. First, measure the area where you would like to plant your hedge or row. You will need the length of the area of planting to estimate the number of trees you need.
When planting, dig a hole for each tree that is three times as wide as the root ball but just as deep. You don’t need to add anything to the planting hole. Place the tree, fill in around the tree with the same soil you took out when initially digging the hole. Finally, tamp down as you fill to cut back on any air pockets from forming, water the tree, then mulch to conserve moisture.
Pruning
Covered in dense, dark, evergreen foliage from the ground up, the “Green Giant” arborvitae needs little to no pruning or shearing. Growing elegantly and consistently, it only needs to be pruned if necessary or for aesthetic reasons. Shear into a desired shape and size, and maintain it throughout the warmer months.
Propagation
Propagate the tree from stem cuttings from July through March. Root cuttings under mist with bottom heat (3000–8000 ppm IBA)
Winter Care Recommendations
If you have young Thuja Green Giant trees and live in a cold and snowy winter climate, you should take some extra precautions and care to help them along during their first winter. If your plants are exposed to strong northerly winds, adhering burlap or a light screen to posts placed in front of the trees, will help shelter them from wind damage. Keep in mind that you don’t want to lay the screen on the plant, or you risk it freezing to it. Therefore, leaving about a foot of space between the post and the plant will likely provide the best results.
hoto by David J. Stang
CC BY-SA 4.0
As far as snow is concerned, be sure that you don’t allow it to pile up on the plant or push it over. Simply move heavy snow piles promptly, before they have a chance to freeze or become a solid mass due to the rapid thawing and refreezing that often happens in winter cycles.
Planting your Thuja Green Giant privacy screen can offer you protection from wind and unwanted views year around. Plant them in your front yard to create a wall between you and your neighbor. Plant them in the backyard for a natural fence. Whatever you choose to do, just provide minimal care and these beauties will thrive. Shop our online plant nursery and privacy tree collection for more privacy screen options.
III. Uses and Benefits
Thuja or Arborvitae plays a large role in the garden, with the taller kinds making wonderful hedges that clip into dense screens or they can be left unclipped to make more informal barriers. Planted alone or in small groups they are excellent accent specimens around the house, in lawns or in shrub beds. They can be used to frame a doorway or entrance, outline a driveway or stand as dramatic solitary specimens. The many unusual forms, with colored or exotically-formed foliage and in many sizes, can be used as interesting specimens too, in beds, rock gardens or gravel-covered areas. Thuja can also be grown in containers of various sizes and used on terraces and decks as vertical or rounded accents that need very little attention to always look good.
- As Screens
Thuja trees make great screening plants. They are naturally dense, upright and lush green all-year-round. They need little or no clipping to maintain an attractive form and can be planted as a screen and left to develop naturally. They soon reach 20 or 30 feet in height, creating a solid barrier that filters wind, noise and pollution and gives complete privacy.
Particularly important for this function is Thuja Green Giant, which has a rapid growth-rate, perfect foliage all year round and a dense form. Since it will grow three feet a year when young, it rapidly fills in and gains height, making an excellent screen very quickly. It can grow unclipped up to 60 feet, so it makes the perfect tall screen too, although with clipping it can be kept at any height.
For smaller gardens, especially in colder areas, Thuja Emerald Green is an excellent shorter screen, quickly growing to around 12 feet tall.
- As Hedges
Thuja trees also make great hedges because they take well to clipping and shearing, so they can be turned into formal hedges easily. They quickly fill-in and become solid and dense, making the perfect backdrop to all kinds of garden designs and styles. If clipped from an early stage they can be as short as two feet, or as tall as 30 feet or even more. By choosing the right variety, a perfect hedge for any climate can be easily grown to almost any size and form. For larger hedges Thuja Green Giant is the outstanding and premier choice, while for smaller hedges in cooler areas Thuja Emerald Green is perfect.
Photo by David J. Stang
CC BY-SA 4.0
- As Accent Specimens
Thuja do not of course have to be grown in rows, and as single specimens or groups they make beautiful accent plants in the foundation planting around a house or in shrub beds. With a wide variety of forms available, from upright to rounded, and in green or golden foliage, there is lots of variety to choose from. Evergreens give stability to the garden and a permanence that other plants lack. Since they can be trimmed, controlling size is easy, so they can be used to frame a door, fill a corner, grow beneath windows and occupy lots of places in the garden where they will be right at home.
- As Container Plants
As well as growing in the garden, Thuja make perfect low-maintenance container plants. A matched pair in large pots makes a welcoming entrance feature, or they can be placed around a terrace or patio. Although all types can be grown in pots, the dwarf varieties are usually the ones chosen, since they will live for many years without out-growing the container and they will need little or no clipping.
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