Although Thuja Green Giant is widely grown, and has become one of the great plant success stories, there are still some things that new growers want to ask. We get lots of questions, but here are five of the most common. Hopefully the answers will help you decide if this is the plant for you, and put your mind at ease with any problems you might be anticipating.
How Fast Does It Grow?
When it comes to planting evergreens for screening and hedges, everyone wants to see that mature hedge as soon as possible. Maybe you have an ugly view to screen, or maybe you want to block out those people who keep looking in. Perhaps you want a wind and noise shelter from a busy highway. There are lots of reasons why we want quick growth, and just as many nurseries and sellers wanting us to buy their ‘fast growing trees’, or other ‘super plants’ that reputedly grow many feet a year.
When it comes to questions like this, some simple research is the answer, and for Thuja Green Giant we have that. Some years back, when this plant was first becoming widely grown, some horticultural scientists at the University of Arkansas decided to check out just how fast these plants really did grow. They took a field they had available, and gathered together all the fast-growing plants around. Among them was, of course, Thuja Green Giant. These were small plants, and they gave them some basic care, like weeding and a little water during summer. After 7 years they measured all the plants, and recorded how much they had grown. The Thuja Green Giant plants had grown taller and bigger than ANY of the other well-known fast-growing trees.
Remember these had been small plants, maybe a foot tall. After those 7 years, they were now 10 feet tall and 5 feet wide. That is a big, solid plant. Had they been planted closer together they would have grown more upright, and not as wide, so if this had been a hedge, they probably would have made 12 feet or even a little more. We know from observation that the most rapid growth takes place in the first few years, so they must have grown 2 or even 3 feet in the first couple of seasons, and then a foot a year for a while, then a bit less than that in the later years. So now you know. If the plants you use are already 3 or 4 feet tall, in 5 years they will be at least 10 feet, and probably more like 12 feet. If you water and feed well and regularly, you can expect a few more feet on that. That is big enough for most screening jobs, and certainly makes a large hedge. Remember, Thuja Green Giant was the fastest tree in the trial, so if you want speed, this plant is simple the right choice to make.
How Tall Does It Get?
This is an important question, because you don’t want monster plants in your garden. This was, and still is, a problem with some other fast-growing trees, particularly Leyland Cypress. Because it was so popular, many people planted that tree where they shouldn’t have. It can grow to be 60 to 80 feet tall, and 20 feet wide – that is one big tree! Thuja Green Giant is fast-growing, but much more modest in its final size – 20 to 40 feet is about as big as its gets, and maybe 12 feet wide. That is still large, so make sure you plant far enough away from buildings, roads and property lines that it doesn’t become a nuisance. Of course, as a hedge that is regularly trimmed, it can be kept much shorter, but if you want a screen, with little or no trimming, give it enough room. You almost certainly don’t need screening over 20 feet tall, and a hedge that tall is very complex to trim.
If your needs are for something under 10 feet, then perhaps you should consider something else, like Emerald Green Arborvitae, which tops out in the 8 to 12-foot size-range. Yes, it is slower growing, but of course you are not asking it to get so tall, so it will still reach the size you want in years, not decades!
How Far Apart Should I Plant Them?
This must be the most common question about Thuja Green Giant. The answer depends of course on what you are planning. If you want an informal privacy screen, or some tall background planting on your property, with little or no trimming involved, then 5 feet apart is about right. You could go more, but of course it will take longer for the plants to grow together and give you a solid barrier. For a hedge you plan to trim regularly, 3 feet apart is about right. Don’t be tempted to go closer, thinking it will fill in faster. Instead the plants will struggle upwards, and yes, they will get tall, but they will remain thin at the bottom, and not make the solid hedge you have in mind.
Do Deer Eat Them?
This is another common concern among gardeners, especially if you are in a more rural area, or on the outskirts of town. Deer are notoriously difficult to judge, and there will always be the out-of-character occasion, but everyone is pretty much in agreement on this question. Unlike most other arborvitae, deer usually leave your Thuja Green Giant plants completely alone. Only under extreme winter conditions, or if you have a large herd that have eaten themselves bare, will you see a deer touch this plant. This makes it especially useful if you have those critters around. You can put in a fence to stop them pushing through, and plant Thuja Green Giant up against it to create a solid barrier.
When Is the Best Time to Trim?
This depends a little on where you live. If you have real winter, with snow, temperatures well below freezing for weeks, and frozen ground, then avoid trimming in winter. in milder areas you can, but as a general rule, anytime between spring and early fall is the best time for trimming Thuja Green Giant. Wait in spring until you see a little growth beginning, and stop trimming a few weeks before the days start to stay regularly below freezing point. If you have hot, dry summers, then avoid trimming at that time too, as the foliage can scorch.
How often you trim depends on how neat you want your hedges to be, and how much water and fertilizer your plants receive. For a casual hedge, once a year is often enough – in fall would be the best time for that. Otherwise, two or three times a year will give you a hedge that always looks smart and neat – a great asset in any garden.