Fastest Tree on Roots – Thuja Green Giant

Seems like we live in an age of speed – everything happens faster – instant messages, instant email, instant meals – and our gardens are in on the trend too. There was a time when we were patient enough to wait years for hedges of yew or hemlock to grow, but today we want our hedges fast, not slow. It often seems that when we need something, along it comes, and with hedges too, over the years, new plants have been introduced that give us the faster growth we are looking for.

The first super-fast hedging evergreen to come along was the Leyland Cypress. This plant has a long and complex history, dating back to 1888, at a grand estate in the British Isles. It took many years for this unique plant to be noticed, and although it became popular for hedges in England in the 1930’s, it was the 1950s and 60s before it arrived in America. Its distribution by Clemson University in South Carolina at that time made it hugely popular in the southern states – even more popular than in Europe. The arrival of this fast-growing plant coincided with the expansion of cities and the growth of suburbs, and it became the ‘go-to’ plant for privacy and screening between the new homes spreading across the landscape.

Leyland Cypress remains justifiably popular, but over time the plants become very large, especially if they are not regularly trimmed. So many hedges simply became too large, and after 30 years or so, there was a need to replace them. As well, in hot places some disease problems developed, making it necessary to find a substitute. Anyway, for practical reasons, it always makes sense to replace an old plant with something different – using the same plant can result in poor growth.

It was at this point – just when it was needed – that Thuja Green Giant came along. Although this tree had first been found in Denmark, the Second World War prevented it being introduced into America until 1967. A single plant was growing at the National Arboretum in Washington DC, but it was only in the 1990s, when that plant had reached an impressive size, that it began to attract attention. Several nurserymen who visited the Arboretum wanted to grow this remarkable plant, and they were given pieces to root and grow. The name ‘Green Giant’ was dreamed up by a nurseryman from Tennessee called Don Shadow, and that great name certainly helped to draw attention to this terrific plant.

There were several things about Thuja Green Giant that got those nurserymen excited. The first was its speed of growth. Young plants grow as much as 3 feet in a year, and sometimes even more. As plants mature they slow down, but in 7 years a 10-foot hedge is virtually guaranteed from the smallest plant, and obviously if you start with 3, 4, or 5-foot trees, they will double in size in just a few years. Nothing else approaches that – not even Leyland Cypress.

What is the secret to this rapid growth? It happens because this plant is a hybrid between two natural species of Thuja – the Japanese Thuja (Thuja standishi) and Western Redcedar (Thuja plicata). Neither of these plants is particularly fast growing. When they get together, however, we see what scientists call ‘hybrid vigor’ – offspring that are stronger, faster-growing and generally tougher than either parent.

Because it is not only in speed of growth that Thuja Green Giant excels, and shows this hybrid vigor. Other kinds of cedar are likely to show browning in winter, but not this one. Others may be particular about the soil they grow in, but not this one. Others suffer from pests and diseases that can make them unsightly, or have preferences for particular soils, but no, not Thuja Green Giant. It doesn’t really matter what kind of soil you have – sand or clay are all suitable, and so are acid or alkaline soils. Dry or wet, all soils are suitable. Only if your soil is regularly flooded can this great plant not be grown. It is very rare to see any kind of pests or diseases on it either, and even if you do it will be very minor and cause no particular concern.

Now if course this tree is a fantastic grower, but it does benefit from some attention. In particular, good soil preparation will give it the best start in life. This means digging the soil well, by hand or with a roto-tiller. It also means adding organic material, like compost, rotted manure or peat-moss to the soil. Some starter fertilizer is an excellent idea too. These basics will give your plants a great start – and give you those growth rates you are looking for.

So will regular watering, especially during the first season or two, while your plants become established. If you are really keen to see the maximum growth this plant is capable off, make sure it doesn’t become dry, and use a liquid hedge food regularly, according to the directions of the particular one you use. Don’t make the mistake of thinking, “If some is good, more is better.” That rule does not apply to feeding your plants – too much can bring problems.

The third way to get the most from your new hedge is to trim it right from the start. “Wait a minute,” I can hear you say, “How can it grow tall if I keep clipping it?” Well you are only going to remove an inch or two each time, so it will hardly affect the height at all. The reason for clipping from the start is to build a dense, twiggy structure to your hedge. Keeping it tight, and building a strong structure will make a hedge that can resist strong winds, snow, and ice. You see, the only problem with this plant is that it cannot produce new, green growth from thick woody stems. As a result, you cannot cut it back if it gets too large. If you have to cut a large amount off, you will have a thin structure that will only very slowly recover and become dense. By trimming a little, but often, you will never have that problem, and you will keep a neat, dense hedge of the size you want for many, many years.

Thuja Green Giant has been planted in the millions, by millions of satisfied gardeners, and it remains the number one choice everywhere it can be grown. If you garden in zones 5 to 8, and you need an evergreen hedge that is 6 feet tall or more, then choose the Green Giant – you won’t be disappointed.