Is Thuja Green Giant Right for My Garden?

When it comes to screens and hedges, the name ‘Thuja Green Giant’ is on everyone’s lips, but a hedge is a big decision you will live with for a long time, so let’s dissect that decision, so that you are sure this is the tree you want to be planting.

How Big a Plant do You Need?

Size matters, and untrimmed Thuja Green Giant are large plants, reaching 10 feet in 7 years in recorded trials in Arkansas, and ultimately growing more than 30 feet tall and 12 feet wide. Of course, trimmed regularly you can keep it under 10 feet tall, but if you want a hedge just 6 feet tall or less, and are prepared to wait a couple of extra years for it to mature, then there are a whole range of plants, from boxwood to Juniper, or for exactly the same look, Emerald Green Arborvitae, that will give you a great evergreen hedge that you can be more relaxed about trimming.

Of course, many people choose Thuja Green Giant exactly because it will become large. If you need screening from a highway, or some privacy from a neighboring tall building, then those extra feet are exactly what you want. Left unclipped the natural density of this tree makes for a solid barrier, and with regular trimming you can easily have 20-foot hedges if you want.

Where do You Live?

Thuja Green Giant is a tough plant, but it does have climatic limits. Its ideal growing range is between zone 5 and zone 8, and even into zone 9. That is a broad sweep across the nation, and if you are in those zones, then you will be making the right choice. But that does also leave a significant area where you might want to look to other hedging plants.

Considering the upper end first, it really depends on your exact climate. In damper zone 9 it will thrive, and certainly do better than Italian Cypress, which is often planted in Florida. There that tree will often suffer from fungal diseases, due to the humidity. In the same zone in the west – Arizona and southern California – Italian Cypress thrives, enjoying a similar climate to its southern European home, while Thuja Green Giant will find the extreme dryness a problem. So in humid, hot zones, stick with Thuja Green Giant, but in drier, drought-prone areas, you will find the Italian Cypress superior, unless you have excellent irrigation.

Looking north, there are significant parts of the country in zones 3 and 4, and even in zone 2. Sadly, if this is you, Thuja Green Giant is not for you. You can make excellent hedges however with its relative Thuja occidentalis, the arborvitae or white cedar. A top form for dense growth and ‘hedginess’ is Emerald Green Arborvitae. This plant is slower growing, and of course in colder areas the growing season is noticeably shorter. Since nothing beats Thuja Green Giant’s three feet a year plus growth rate when young, Emerald Green does still manage a respectable 18 inches a year in good growing conditions, so it will mature soon enough.

Do You Have Sun?

Like almost all evergreens, Thuja Green Giant is best when grown in sun. If you are looking at a partially shady spot for your planned hedge, then how many hours of direct sunlight does it get? Six hours a day, certainly in spring and summer, would be a minimum, and for a really dense hedge sun all day is best. If you have shade, then consider other possibilities for an evergreen hedge. The yew tree (Taxus) is the classic shade hedging plant, but boxwood is also a good choice. You might also move into broad-leaf evergreens, like English cherry laurel, or holly is also a good choice.

What is Your Soil Like?

Because it is a hybrid plant – a natural cross between two different species – Thuja Green Giant is tougher and more adaptable than either parent. So it grows well in almost all types of soil. From sand to clay, and in both acidic and alkaline soils, it does well. If you do have very sandy soil, prone to rapid drying, and lacking in nutrients, then the classic solution of adding plenty of rich organic material when planting is still the best solution. Using plenty of fertilizers may solve the nutrients shortage, but they will be rapidly lost, so you will need to do a lot of feeding. As well, they won’t tackle the water issues at all.

Organic material solves all three problems. It retains moisture, it provides a steady nutrient supply as it decomposes, and the humus created – a term for the long-term, very slow decaying parts of organic material – acts as a store for the mineral nutrients in the soil, preventing them from washing out in drainage water. An annual mulch with more of the same over the root zone will keep that soil in good shape, and reward you with rapid growth, and rich, deep green plants.

Not every garden is dry, and some suffer at the other end, with constantly wet soil. Perhaps you live in a low-lying area, or the place for this hedge is in a hollow. Maybe you are beside a stream or lake. Whatever the reason, if your soil is constantly wet then Thuja Green Giant will struggle. Most plants need oxygen at the roots, and wet soil is almost always low in oxygen, so roots are weak, and diseases easily attack them. The best strategy, and one that is often successful, is to mound up the earth in a long row, raising it at least 6 inches above the surrounding ground. If you do this by throwing up soil from trenches on either side, making the ridge at least 3 feet wide, and preferably wider, then you will also create natural drainage channels around your mound. Open them up for water run-off at the lower end, and you now have a well-drained planting area. It is some work, but the payoff is the great result. Now Thuja Green Giant will thrive, with good access to both water and oxygen around the roots. Problem solved.

Do You Have Deer?

Most Arborvitae are popular with deer as winter food, but Thuja Green Giant stands out as being deer resistant. This is not the same as ‘deer proof’, because of all grazing animals, deer are highly unpredictable. Young, inexperienced animals will test just about anything, and can damage plants even if they quickly give up. Very hungry deer, in the depths of winter, will eat just about anything too, so personal experiences can differ. Allowing for that, the consensus is that Thuja Green Giant is among the best of the deer resistant evergreens, so it’s a top choice is you are in an area where deer come around in winter.

Hopefully this run-down has been helpful in reaching a decision that will give you the best results. Thuja Green Giant is a great plant for many locations, but it is better to make a different choice than to make a wrong one.