There is no question that among evergreens, Thuja Green Giant is the most recommended and the most popular of them all. When it comes to rising to the top of the poles, it’s a case of, “May the best plant win”. So what qualities does this plant have that allowed it to rise to the top? In answering that question, we can learn more about this plant, its suitability for your garden, and what it is about it that has proved so successful. Now read on. . .

The Origins of Thuja Green Giant

When we think of famous places for producing plants, Denmark is not a country that immediately comes to mind – yet it is there we begin our story. Dorus Poulsen was a keen amateur botanist and gardener, and in 1878 he started a nursery, growing and selling plants, near a grand manor house called Frijsenborg. There he became known for his rose breeding, and the Poulsen name was associated with quality and innovation. When Dorus retired in 1925 his sons took over the nursery, and it was probably one of them, who, in 1937, found a seedling that would eventually become famous. Here the picture is a little murky, because we don’t know if this was something produced by a breeding program – the Poulsen family were all keen on plant breeding – or just an accidental event that caught their keen eye. In any case, within a short time World War II would engulf Europe, and seedling evergreens were not of much importance in that life-or-death struggle.

It is 1967 before we pick up the trail again, now at the National Arboretum in Washington D.C. They received a shipment of plants from a Poulsen nursery – the company now had a number of branches- in Kvistgaard, north of Copenhagen. There were several different plants of Thuja evergreens, and these were planted out for observation in a nursery area. Several staff members noticed the speed of growth of this plant, which was very rapid in the early years, and in 25 years this plant was 30 feet tall – a remarkable achievement. In the early 1990s people were starting to pay attention

What is Thuja Green Giant?

So what was this plant? The botanists could see that it was a Thuja, a relative of the eastern Red Cedar, which is a common plant throughout the north-east. Because of its vigor and rapid growth, they suspected it was a hybrid – a cross between two natural species – but they didn’t know. The records didn’t help much, and beyond tracing it back to that Poulsen plant found in 1937, they didn’t have much to go by.

However they now had DNA analysis available, a great tool for solving these kinds of mysteries, and using that a team of scientists from the major American botanical gardens figured out what they were dealing with. This mystery plant really was something remarkable and never seen before – a hybrid between the Western Redcedar, Thuja plicata, and the Japanese Arborvitae, Thuja standishii.  One grows in Oregon and Washington state, and the other grows in Japan. We may never know exactly what happened in that nursery in Denmark 80 years ago, but it produced a trans-pacific hybrid, full of what plant breeders call ‘hybrid vigor’.

Why Does Thuja Green Giant Grow So Fast?

When two plants are bred together, all the best forms of the many genes it has hide the bad forms, that naturally accumulate over the millennia. So a hybrid plant is running on all cylinders perfectly, creating this hybrid vigor, and this is the simple explanation of why Thuja Green Giant grows as fast as it does. Growth rates of over 3 feet a year have been seen in young plants. In a trial at the University of Arkansas, tiny plants grew 10 feet tall and 5 feet wide after only 7 years. This was a trial of many hedging plants, and the fastest was the Green Giant. This is the major reason for the popularity of this plant – its growth rate. If you need large evergreens in a short time, then Thuja Green Giant is the number one choice – right on top of the list.

Deer Don’t Touch It

Deer are a serious problem for some gardeners, and they can and do decimate plantings. Some kinds of Thuja are popular winter food, and a hedge or screen can and is often stripped completely of its lower branches – ruining the work of decade or more.

Deer are very unpredictable, and when driven by hunger will eat just about anything, so it’s impossible to make an absolute statement, but the evidence is that Thuja Green Giant is almost always left alone. Spraying with a deer repellent in winter, especially when plants are young, is always a good idea, but compared to other Thuja, deer resistance is another reason why Thuja Green Giant is at the top of the polls for large evergreens.

Lack of Pests and Diseases

That hybrid vigor that produces such rapid growth also protects Thuja Green Giant from any serious pests or diseases. This is unlike some other evergreens, and one reason for the success and popularity of this plant is its usefulness in replacing old hedges that have become diseased

How Winter-hardy is Thuja Green Giant?

If you live in zone 5, or anywhere warmer, then there is no question that this plant will thrive, and it will survive winter in a perfect green state. If you have heavy snow, then any evergreen needs to be trimmed from time to time, so that it doesn’t have long side branches that can bend and break under wet, heavy snow. But as for winter burn, browning, or the bronzing that plagues some evergreens, those will not be a problem.

If you live in colder zones, then Emerald Green Arborvitae is a better choice. It’s hardy to zones 2 or 3, making it a top choice. At the other end of the scale, if you live in zone 9, or in a hot, dry area like Arizona, then the Italian Cypress is the best choice. It’s still fast-growing, and it is acclaimed for its drought-resistance.

Looking at these things -from growth rate to hardiness – it’s easy to see why Thuja Green Giant has risen to the top of the list for larger evergreens, whether you need an informal screen or a trimmed hedge. Just remember that it does get large, so don’t use it for hedges less than 6 feet tall, or plant it in narrow spaces, or too close to buildings. It’s a great plant, but sometimes something smaller is a better choice!