Spring is just around the corner now, and many people are thinking about hedges and screening plants. That means thinking about Thuja Green Giant, the biggest selling and most popular screening evergreen there is. Before making that investment of money and time, everyone has questions about this plant. Let’s look at the most frequent questions and give some much-needed answers to them.

7 Questions About Thuja Green Giant

  • How fast does it grow?
  • How big will it grow?
  • Is it eaten by deer?
  • Where will it grow?
  • How far apart is it planted?
  • Where did it come from?
  • How do I care for new plants?

How fast does it grow?

No one wants to wait forever to see a mature hedge, or have a screen do its job of screening an ugly view or protecting you from prying eyes. So the first question on everyone’s mind about Thuja Green Giant is just exactly how fast does it grow? Everyone will tell you ‘fast-growing’, ‘quick-growing’, ‘super-fast grower’, but what does all that really mean? Of course it’s hard to be definitive, since every garden is different, in a different growing zone. Soil varies, and so does the input of the grower. But still, there must be some objective data out there – someone must have run a trial and compared Thuja Green Giant to other popular hedging plants. Well they did. At the University of Arkansas, when this plant was still new on the scene, the plant department cleared a field, and planted a selection of trees and shrubs commonly used for screens and hedges. The started with small plants given them by local nurseries, and after planting, gave them some fertilizer, and watered them during dry spells. Otherwise, they did nothing special. Each year the researchers measured the plants and kept notes.

After seven years they took all their figures and tabulated the results. Thuja Green Giant outgrew every other plant and it had no pests or diseases in the whole time. That tiny little plant had grown to a full ten feet tall – that’s right, almost twice as tall as a person. That might not be the ‘5-feet a year’ you have seen advertised, but that figure is the maximum possible under the most ideal conditions, and no plant will grow that fast year after year. Ten feet is bigger than most hedges you will ever want, and a 10-foot screen will block almost anything anyone wants to block out. So don’t worry, you won’t have to wait long to get the result you are looking for.

How big will it grow?

If you are not planning to trim regularly, then you want to know how tall this plant will grow, or you may find yourself engulfed in green. Thuja Green Giant will grow to at least 30 feet tall, in less than 30 years, and it will be 12 feet wide. If you are not planning to trim, then plant at least 6 feet away from property lines, fences, walls and buildings. Don’t plant in front of windows, or even within 6 feet of either side of a window or doorway. Don’t plant it 2 feet from your driveway or paths either – for obvious reasons.

Is it eaten by deer?

This is always a big concern for people who live in areas where deer come near in winter. They can certainly do a lot of damage in a very short time, and these unpredictable animals are often willing to eat almost anything if they are hungry enough. So its not possible to say that a deer will NEVER eat a Thuja Green Giant, but everyone who has grown it around deer reports that they leave it alone. Deer eat a lot of other plants, including Emerald Green Arborvitae, but the green giant is usually left completely alone.

Where will it grow?

Thuja Green Giant is hardy from zones 5 to 9. That means it will grow well in areas where the normal minimum winter temperature is minus 20 degrees. It also means it will grow in areas where the temperature never falls below freezing. It will do best in areas without very humid and hot summers, and it grows most easily in places with rain during most of the year. If you are in a cold area, like zone 3 or 4, go for Emerald Green Arborvitae. If you are somewhere where rain is rare, especially in summer, Italian Cypress will be more useful to you, with its great drought resistance. Neither of these will grow anywhere near as fast as Thuja Green Giant, but they are excellent substitutes in extreme areas.

How far apart is it planted?

To create a screen or windbreak, space your plants 5 to 10 feet apart in a single row. A double row will give you a denser screen, and for that, make the two rows 5 feet apart, and put the trees 8 to 12 feet apart, staggering them in the rows. For a hedge, space them between 3 and 5 feet apart. For a double row, make the rows 3 feet apart and then put the plants 5 to 8 feet apart in each row. Wider spacings take longer to fill, of course, but by using fewer plants you can save some money.

Where did it come from?

Thuja Green Giant is a cross between Japanese Thuja (Thuja standishii) and Western Redcedar (Thuja plicata), which is a common tree throughout the Pacific Northwest. As a hybrid tree, it combines the best of each species, producing vigorous, rapid growth and making a hardy tree that grows well right across America. It was originally found in a nursery in Denmark belonging to the Poulsen family, in the late 1930s. The Second World War got in the way, and it wasn’t until 1967 that some young plants were sent to the National Arboretum in Washington, D.C. In the 90s visiting nurserymen who saw it – by then 30 feet tall – were excited about this fast-growing new tree, and they were given pieces to grow. Don Shadow, who was a nurseryman from Tennessee, was the person who coined the name ‘Green Giant’.

How do I care for new plants?

Once you have planted your new trees, the critical thing in the first year or two is regular watering. You need to encourage your new plants to spread their roots out into the surrounding soil, so that they can draw on water deeper down, and become thoroughly drought resistant. Once a week is not too often during the first year, and if you have a newly planted hedge, and an extended dry period, then twice a week is probably wise. Once established Thuja Green Giant is very tough and reliable and is certainly not a plant that needs much care at all, in the longer term. It’s a smart choice if you would rather spend your time doing something other than caring for plants.


Hopefully these answers to this list of frequent questions will help you decide if this is the tree for you. Knowledge is power.