Does Thuja Green Giant Attract Pests or Diseases?

The short answer to this question is ‘NO’, but despite the toughness and resistance of this great evergreen, problems can very occasionally develop, some caused by growing conditions and some by specific pests or diseases. Don’t worry, these problems are rare, and most gardeners never see any problems at all with their plants. So that you can be equipped to deal with anything that may seem to be going wrong, it’s time for some advice. So here are some things you may see, and what to do about them.

My new plants look dull and the ends of some of the branches are turning brown

New plants of Thuja Green Giant need plenty of water. When they are first planted they only have roots in the root ball from the pot. Especially if the surrounding soil is a bit dry, those roots won’t be able to take up water and this will first show by the ends of the branches bending over and beginning to turn brown. If the weather is warm you may need to water your plants every second day for the first few weeks after planting. Otherwise water them at least once a week. New plants need plenty of water to establish in your garden, so don’t forget them – they need you!

My plants look yellowish, not bright green, and they aren’t growing

Especially when young, these fast-growing plants need lots of nutrients. They don’t have a big root system yet to get enough from the soil around them. So they can easily run low on essential food elements, grow more slowly and show a characteristic yellowing of the leaves. If you see this, it is time to start fertilizing your plants. For young plants choose a water-soluble fertilizer formulated for evergreen hedges and apply as directed. If your plants are older, then a granular fertilizer will be lower-cost and quicker to apply. Modern slow-release fertilizers cost a little more, but they only need to be applied once a year and they will continue to feed your hedge all season long.

There are strange-looking clusters of dry needles hanging in the tree

These could be bagworms. This is a common pest of some arborvitae trees, and it is occasionally found in Thuja Green Giant. Since this tree is so tough and hardy, they are only very rarely attacked by this insect. If you see what look a bit like hanging greenish or brown ‘cones’ one or two inches long on your plants, then you have bagworms. Inside there is a green caterpillar that will eat the leaves, and can make parts of the bush very bare. If you just have a few, or your plants are young, then simply pick them off and throw them into a bucket of hot, soapy water. The caterpillar makes the bag out of silk and pieces of the plant it has chewed off. Once you remove the bags your trees will quickly grow back. If you have larger bushes, or a lot of bags, then spraying with Bt (pronounced ‘bee-tee’) or Spinosad. Ask at your local garden center for specific brands of these safe, non-toxic sprays made from naturally occurring microbes. These products only kill caterpillars and they will not hurt other insects, animals or humans. Since bagworms usually don’t attack Thuja Green Giant at all, you will probably never see this pest on your hedge.

I have something sticky on my leaves, and black powder on them too

Again, this is a very rare problem, but it can happen. The stickiness comes from sap being taken from the plant by scale insects. The black (or occasionally white) growth is fungus growing on the sugary sap. Neither the sap or the fungus will hurt your plants, but the little scale insects, that look like brown pimples on the stems, do weaken the trees and can cause browning. Luckily Thuja Green Giant grows so fast and so vigorously that scale is rarely a problem. If you see areas like this, usually you can trim them away, clean up carefully, feed and water your trees and they will quickly recover. Only very rarely, perhaps if your trees are growing in poor, dry soil, will scale be bad enough to need spraying. Ask at your garden center for something suitable.

Poor growth, and branches are dying

Although your trees need water, they can have too much of a good thing. If the soil is constantly wet no air gets to the roots, and they die and rot. If your plants are not growing, well, and parts of them turn brown and die, or if a whole plant in your hedge dies, you may have root rot. Once the symptoms show it is hard to do anything, so first make sure you plant in an area with good drainage. If you need to plant in a badly-drained spot, then mound up the soil and plant on that mound. If the plants are a few inches above the soil the roots will get more air. If you have an irrigation system, check that you don’t have a leak, or reduce the watering time. Your plants should get plenty of water, but the soil should become a little dry in between each watering.

In the End

Thuja Green Giant is one the most pest and disease resistant plants you can grow, so if you give them a little basic care with water and fertilizer the chances are very good you will never see any problems at all. Now that you know what to look for, you can take some simple steps to deal with any rare problems that might come along.

Where Did Thuja Green Giant Come From?

Thuja Green Giant is the most popular and widely-grown hedging plant off all time. Millions of satisfied gardeners enjoy the benefits of its rapid growth and easy care. Most people take plants for granted, thinking they just ‘are’, but perhaps you have wondered, “Where did this plant come from? Does it grow somewhere in the wild? Did some scientists or nursery-person create it? Is there a connection between its origin and how fast-growing and sturdy it is?” Let’s see if we can answer these questions.

First of all, Thuja Green Giant is not a wild plant – it is the product of gardening itself, which has brought into being thousands and thousands of plants for us to eat and enjoy. Selecting certain plants for their special features is as old as agriculture. If we could only put on our tables plants that can be found growing wild, then we would have to ignore almost every fruit and vegetable we eat. There are plenty of ornamental plants growing in our gardens that can be found growing wild somewhere in the world, but many more that have been created for our enjoyment. Thuja Green Giant is such a plant, with a long and complex history.

The Origins of Thuja Green Giant

About 150 years ago, in 1878, a gardener and amateur botanist called Dorus Poulsen started a nursery to grow and sell plants, in Frijsenborg, Denmark. It soon became famous and very well-regarded, especially for its roses, which Dorus bred himself. He opened several branches across Denmark, and when he died in 1925 his sons continued the business, producing many new plants from their breeding programs. In 1937 they noted a novel Thuja growing, but it is not clear if this was an accidental seedling, or part of some breeding they had done.

History stepped in, World War II broke out, and Europe had more important things to think about than plants. After the war the nursery returned to normal activity, and eventually, in 1967, thirty years after that first chance discovery, the National Arboretum in Washington D.C. received a package of plants from one of the Poulsen nursery branches, in Kvistgaard, Denmark. Included in the shipment were several different Thuja plants, which the Arboretum staff planted out in a nursery area at the arboretum. The speed of growth on one of them was noticed, and that plant started to get some excited reactions when it reached 30 feet tall in 25 years.

When the staff looked back through their records, they quickly found that the book-keeping had been less than perfect. The plant numbering had become confused, and they could not figure out which Danish plant ths was. Suspecting the plant was a hybrid, something that had never been seen before among Thuja plants, three scientists became interested, and with the recent development of DNA analysis, they saw a way to solve the mystery. These three scientists, Susan Martin, from the National Arboretum; Robert Marquard, from the Holden Arboretum in Ohio; and Kim Trip, from the New York Botanic Garden got to work, and succeeded in analyzing the DNA all the plants at the Arboretum, and comparing it to that of the parents of those 1967 plants from Denmark.

A Hybrid Child

The scientists were able to link this mystery giant Thuja to the plant found in 1937 at the Poulsen nursery, and showed that it was indeed a hybrid between two species of Thuja. One parent was the Western Redcedar, Thuja plicata. This forest giant can reach 200 feet in height, and grows wild in Oregon, Washington State and British Columbia. It is the source of the lumber called red cedar, which is ideal for garden construction and furniture, since it is naturally resistant to decay and needs no paint or preservatives.

The second parent was the Japanese Arborvitae, Thuja standishii. This plant grows wild high in the mountains of the Japanese Islands of Honshu and Shikoku. It is also cultivated in Japan for its wood, which is aromatic and waterproof, and is used for sake cups and barrels.

Just what had happened in that nursery in Denmark in the 1930s is not clear, but somehow a trans-pacific hybrid had been created, a plant that had beautiful foliage all year round, grew vigorously and very quickly, and was graceful, upright and worthy of a place in every garden. Botanist already new that crossing together two different species of plants produced what they call ‘hybrid vigor’ – strength, hardiness, speed of growth and resistant to pests that neither parent has. Thuja Green Giant had hybrid vigor in spades.

Thuja Green Giant Takes Off

A nurseryman from Tennessee called Don Shadow was the person who suggested the name ‘Green Giant’, and a major US nursery group called Wayland Gardens decided to multiply and promote this plant to home gardeners. They propagated thousands of young plants of Thuja Green Giant from that original plant, and began a program to describe its benefits to gardeners. This great evergreen lived up to everything promised of it, and by 2004 it was the top-selling plant at Wayland Gardens. Other growers picked it up, and since there was no plant patent on it, everyone could freely reproduce it. In the south-east, many gardens had old hedges planted in the 50s and 60s, which were diseased and needed replacing. So the timing was perfect for the introduction of a new hedging evergreen. Millions of plants were sold to replace those old hedges, and Thuja Green Giant, the child of two trees from different continents, who met on a third, became the most popular and successful hedge plant in America.

Maximize the Growth of your Thuja Green Giant Hedge

Thuja Green Giant has become the most popular choice for evergreen hedges across most of the county. Everyone is using this fast-growing tree to build beautiful hedges for privacy and as the perfect background for their gardens. This plant so popular because of its fast growth rate, and such a tough plant will thrive and grow well in lots of different situations. It is a living thing, though, and it performs best with a little help from us. Here are some simple tips will make sure that your Thuja Green Giant Hedge grows at its fastest rate, soon maturing into the perfect hedge you are looking for.

Preparing the Soil for Thuja Green Giant

Making sure your plants have everything they need when you plant them is the first place to start. Once you have decided where your hedge is to run, prepare the ground by digging it as deeply as you can. For a smaller area you can hand-dig to the depth of a full-sized spade. For longer distances using a rototiller is a good idea, and will make the job so much easier to do. The bigger the machine the better, and it is easy to rent a full-sized professional machine for a day, and do a great job. You also want to have some organic material to add to the soil. This can be almost anything, from garden compost to peat moss, but the richer the material the better. Spread several inches of organic material over the area for the hedge, to a width of three feet. If the area is already lawn, cut it short and dig or till the grass into the soil. It will rot and add nutrients for your hedge. If it is rough ground, go over it first with a spade and dig up any large weeds, removing the roots as much as you can.

The secret with rototilling is to take your time. Go over the ground as slowly as possible, using the lowest speed for the machine, and allowing it to dig itself into the ground and move forward slowly. Till the area two or even three times, until the tiller is as deep as it can go. Till a strip three feet wide, and when you are done, rake it level, removing any weeds.

Planting Thuja Green Giant

The temptation to pack your plants very close together is understandable, but a big mistake. You need to allow enough room for the plants to develop, and spread sideways to make what will become the bottom of your hedge. If you pack them close together there is a danger that in a few years the lower part will become thin and open, so you never build a thick, strong hedge right to the ground. The minimum spacing should be 3 feet apart – Thuja Green Giant is so quick growing that it will very soon fill that gap. For a tall hedge or a natural screen you can even go wider, 4 or 5 feet, and for a very dense screen a double row, with the plants staggered, is even better.

At planting time, water the pots thoroughly the night before, because you never want to plant dry root balls. If there are roots circling around inside the wall of the pot, cut through them in a couple of places to encourage the roots to spread out and find that rich organic material you added. Don’t wait to water your plants until after you have put back all the soil.  Do it when about two-thirds of the soil has gone back. Then add the final layer of soil. That way you have made sure the water is well down in the planting hole, and not just on the surface.

Water and Fertilizer for Thuja Green Giant

To get the best start with your hedge, a regular watering and fertilizing program is important. In the first growing season, water your plants once a week, and twice a week during hot weather. Running a trickle hose along the row and connecting it to a tap is the easiest way to really soak your hedge without taking up much of your valuable time. For the quickest growth in that first season, water-soluble fertilizer gives the best results. This soaks right down into the root zone, and it is quickly absorbed and used by the trees. Look for a blend made for evergreen hedges and follow the directions. Normally these kinds of fertilizers are used every two to four weeks. Make sure you follow the dilution directions carefully, as too much is not a good thing. If you have planted a large hedge, a hose attachment for putting down the fertilizer will save you a lot of time.

Once your hedge is established, switch to a granular fertilizer program. These are usually applied in early spring and again in mid-summer, but some modern types are slow-release and only need one application a year. Alternatively, you can continue with water-soluble feeding during the second year as well, which should give you a slightly better growth rate. After that granular fertilizer work just fine and save time too. Continue to water during dry-spells, as a good water supply is needed for maximum growth, but allow some drying of the soil between each watering. Water thoroughly at intervals, rather than small amounts all the time. Don’t let the soil around the roots dry out completely, especially during the early years. Established plants are very drought-resistant, but they won’t be growing when the soil is dry – just staying alive.

Even though Thuja Green Giant is a naturally fast-growing plant, a little care will give you the quickest and best results possible. Like raising children, care in the early years makes for strength and health in the later ones.

The Right Soil for Thuja Green Giant

Your soil is the foundation of your garden, and the support for everything that grows in it. This means that no matter what you plant, considering your soil is always going to be step one. Thuja Green Giant is often among the first plants bought for the garden, since hedges and screens made from fast-growing plants are the first step in building privacy, protection and a sheltered environment for more demanding plants. Fortunately, Thuja Green Giant is a plant that is very tolerant of a wide range of soil conditions, so most gardens can accommodate it without problems developing. Even so, since this is vital information for all your later plant choices, this early stage is a good moment to check out your soil and collect some basic information.

Find Out Your Soil Type

There are two important aspects to soil that you need to know, and both are easy to find out. The first one is your soil texture. This is how fine or coarse the particles in your soil are, and it is what is meant when we talk about sandy or clay soils. There is a simple way, with no tools required, to find the texture of your soil, and it is one of the first things to do when you start working with your garden. First, scoop up some soil from a few spots in your garden, and mix it together. Then take a couple of teaspoons of that soil, and place it in the palm of your hand. Add a few drops of water, and mix until the soil stick together and feels like Play Doh.

Now make a ball and squeeze it in your hand. When you open your hand, is it still in a tight ball? If not, and it is falling apart, then your soil is Sandy Soil. Now squeeze and push the ball of soil out of your palm over your first finger, into a ribbon. Do this until the ribbon breaks under its own weight. If the ribbon is only an inch long, then you have a Loam Soil. If the ribbon is between one and two inches long, you have a Clay Loam Soil. If the ribbon is longer than two inches, you have a Clay Soil. If the soil also feels gritty, no matter how long the ribbon, then you have a sandier version of these three types of soil, and one that will drain well, but perhaps need more frequent watering. The less gritty it is, the more clay there is in it, and the longer your soil will take to drain.

The next important thing you need to know is the acid balance of your soil. You can easily test this with an inexpensive kit from your local garden center or hardware store. Acid balance is measured on a special scale called the pH scale, and 6.5 is the best number to have for most plants. If you have that, or a lower number, then you can grow acid-loving plants. Soil around the number 7 is called neutral, and above 7 is alkaline.

What Soil Type does Thuja Green Giant Like?

Fortunately, Thuja Green Giant is very adaptable and will grow well in all four main types of soil. In more sandy soils it is best to add lots or organic material when planting, and to water more frequently. Clay soil too benefits from organic material, since it opens up the soil and improves the drainage. If you have a clay soil, then only water when it begins to dry, as this kind of soil drains slowly. If you have the ideal soil – a loam type – then you are lucky, and you will have an easy garden to grow plants in, but even if your soil is sand or clay, Thuja Green Giant will do well if you put a little extra effort into preparing the soil. If you have a very sandy soil, then extra water and fertilizer will be needed to get the maximum growth from your plants.

With the acid balance too, this is a plant that is happy in all types of soil, from acid to alkaline, so it will thrive, no matter what your soil type is. You will not have to try and modify it, although if your soil is very acidic, with a pH below 4.5, adding some garden lime to the soil when preparing the planting area will help release extra nutrients to encourage the maximum growth for your Green Giants. Even in very alkaline soils, over 7.5, this plant will thrive, unlike many other evergreens.

The one thing you should pay attention to is drainage. Does water lie on the soil surface for more than a few hours after heavy rain? If it does, you have poorly-drained soil, and it is a good idea to plant your hedge on a ridge, by mounding up the soil in a row. This will lift the roots out of the wet soil, and keep them a little drier during the important establishment stage of growth.

The information you gather about your soil will really help you make good choices for future garden plants, and help you plan watering and fertilizer applications. Whatever your soil, you can be sure that Thuja Green Giant is such a tough and reliable plant that it will flourish in all but the most adverse conditions. Just a little care will make all the difference.

Correct Spacing for Thuja Green Giant

Thuja Green Giant is the most popular screening and hedging plant for a wide area of the country. It is so fast-growing that an attractive, durable screen or hedge can be created in a few short years. When planning to plant a screen or hedge, how far apart you are going to place your plants is the first decision you must make. Spacing depends on several factors, and it is going to have a big effect on how soon you have an effective screen, and how durable that screen is going to be. It is definitely worth putting some serious thinking and planning into this step, before purchasing your trees.

Why Close Planting is a Bad Idea

The most common mistake made is putting the plants too close. This becomes more of a problem the taller you want your final screen or hedge to be. It is always tempting to go for an ‘instant hedge’ and pack the plants as closely as you can in the row. This might give a quick effect, and for a shorter hedge it can even work out OK, but it usually just creates future problems instead. One obvious problem is that by packing the root balls together, there is no room for future root development, so the plants become stunted and starved for food – meaning slower growth over the long term. The second problem is that plants naturally compete with each other for light, so by crowding them together they grow tall and skinny, and the lower branches quickly die, leaving your hedge bare and thin.

A tall thin hedge is also much more likely to bend over or even break in a storm, strong winds or a blizzard. The thin stems just can’t hold up the branches once they are weighed down with water, ice or snow. That is that last thing you want to happen to your hedge, so you need to encourage sturdy growth, and to do that means allowing the plants more room.

Choose the Right Spacing for the Result You Want

Grown as a single plant, Thuja Green Giant will be about 12 feet across in 12 years or so. That means that a screen even at that spacing will eventually form a solid barrier. Most of us don’t want to wait that long, so something closer makes sense. In trials that were done at the University of Arkansas, very small plants were 5 feet across in 7 years, meaning that the typical 4-foot or 5-foot tree bought for a screen or hedge will be that wide in just 2 or 3 years. So, if you space your plants 5 feet apart you will get the best combination of sturdiness and speed to complete your screen. If you have more time, or less money, then spacing between 5 and 10 feet wide will always give you a solid screen, some just take a little longer to get there.

For hedges, closer spacing is best, because you want a denser surface to trim it into that beautiful solid, green hedge you are dreaming of. This means that for hedges, spacing your plants between 3 and 5 feet apart will give you perfect results in a very short time.

Single or Double Spacing?

The answer to this question depends on how solid you want the barrier to be, and how much space you have. Double spacing – where we plant two rows, not one, with the plants staggered in the rows to create a zigzag pattern – is the best way to get a really dense screen that will block wind, noise, dust and drifting snow. It will be wider, so you need more room, and it takes a few more plants. However, since the spacing in the rows is increased, it actually doesn’t take a whole lot more plants at all. For example, if you are planning a single row spaced 5 feet apart, then a double row, with the rows 3 feet apart, and the plants 8 feet apart in the rows, still gives you plants that are 5 feet apart on the diagonal. (Some quick school geometry with Pythagoras’ Theorem will prove that). This means that for a 150-foot screen, you need 30 plants with single spacing, and only 8 more for a double row. Those few extra plants will give you a really solid and dense screen just as quickly, and a superior result in the long-term.

Planning and Planting Your Hedge

The first step is to measure out the length you want your hedge or screen to be. Then try dividing that length by 5 for a screen, or 3 for a hedge – how many plants is that? Let’s take an example. I want a hedge that is 123 feet long. If I divide that by 3 I find I need 41 plants. If I go with a wider spacing of 4 feet, that number comes down to 31 plants. Is the saving worth the slightly longer wait for that perfect hedge? Only you can answer that question.

Once your plants arrive, and you are ready to plant – something we have looked at in other blogs here – it is important to place all your plants in their final location before beginning to plant. Put the first and last plants half your chosen planting distance from the place you want the hedge to end, and then place the plants in between. Adjust the positions so that every plant is evenly spaced BEFORE you start planting.


Thinking about spacing in the planning stage, and making the right decision before you place your order, is time well-spent, and will give you the best possible result for your investment. Thuja Green Giant is a tough, adaptable plant, but it will give you its best if you help out with a little planning. You will soon have that screen or hedge you have been dreaming about.