With the first flush of spring growth well underway, it won’t be long before your hedges need trimming. Hedges are the basic architecture of many gardens, and the privacy and shelter they bring are essential for creating a personal garden space. Often they have a practical purpose, sheltering you from neighbors or traffic, but they also give form and structure, creating a stage for your plants to strut their stuff on.

Popular hedging plants like Thuja Green Giant have a natural density that makes it easy to grow them into solid green walls, but you also need to treat them right, and good hedges follow some simple rules for success.

Follow These Six Tips for the Perfect Hedge

• Trim regularly – the more you trim, the denser it gets
• Trim while your hedge is young – waiting till it reaches full-size is a mistake
• Trim in the right seasons – too early, or too late, can cause problems
• Slope the sides – an inward slope keeps the bottom green and healthy
• Narrow the top – round or square, a narrow top sheds snow and ice
• Feed and Water – like a lawn, you need to replace what you removed

Trim Regularly

Old-time gardeners don’t waste their words. They say, “The more you trim, the denser it gets”, and they are right. When you cut the tip off a growing stem, of any plant, it produces several new shoots a little below where you cut. Buds at the ends of stems produce a plant hormone that stops the dormant side buds lower down from growing. When you cut off that bud they are released from control, and spring into action. Think of how many tips you cut off with your trimmers going over a hedge. Multiply that by three or four, and you can see how many new stems you have. Many stems give us the crowded, dense growth that makes the perfect green wall. It really is that simple.

Trim from an Early Age

If there is one single mistake made when hedges are planted, this is the one. It seems logical that you would leave your hedging plants, like Thuja Green Giant, to grow to the size you want and then start trimming. But logic is not your friend on this one. A solid hedge that is resistant to wind and snow needs a strong internal structure of many short branches. Taking off just a little growth as your hedge is expanding will give you that sturdy structure. If you wait until it has grown taller, then all the density will be on an outside ‘skin’, and that makes your hedge vulnerable.

Start trimming as soon as you see new growth on your new hedge. Just take off an inch or so, regularly, and you will see how quickly it becomes solid. It will still grow up almost as quickly as if you left it alone, but this time you will have many branches, making a tough and sturdy hedge.

Trim in the Right Seasons

There is a rhythm to plant growth, and to the seasons. The longer days and warmer temperatures of spring trigger a big flush of growth, drawing on reserves stored in the previous year. The buds for that growth develop in late fall and early winter of the year before. So you need to let that first flush mature before trimming, as it is the new foliage that keeps your hedge dense and green. If you cut it all off, the older parts now have to make new buds to replace it, and the older leaves soon fall off, keeping the surface of your hedge always thin and weak.

To allow room for that new growth, without letting your hedge get bigger and bigger, you need to trim in fall, leaving all winter for the new buds to form. This also gives you perfect, tight hedges in winter, when they are especially prominent and visually important. When to make that last trim of the season depends on where you live. In colder area you should allow a full month before the normal beginning of cold temperatures and the chance of ice and snow – the odd morning frost is fine. That probably means mid-September is the latest time. In warmer areas you can trim later, often up to the end of November, depending on your climate.

Once the spring flush has started to darken in color, trim it, leaving a couple of inches of that fresh new growth. That trim will stimulate some more growth – a lot in a young hedge, less in an older one. How many times you cut between now and that vital fall trim, is up to you. At least once is usually necessary, and that will keep your hedge both neat and dense. For a super-hedge, make that two, one in early summer, and another in early fall, if you are in a warmer area.

Slope the Sides

This is another secret that is often ignored. The top growth of a plant is always more vigorous, and longer, than the lower growth. If you trim the same amount from all over your hedge, it will become fatter on the top, and narrower lower down. This will shade the lower parts and reduce their growth. In a short time the lower branches will die, and your hedge will be bare for several feet at the bottom – exactly where you want dense green growth.

So always slope the sides inwards just a little. You will be cutting more from the top than the bottom, but don’t worry about that. The less you cut from lower down, the better, as long as it is neat and flat. The best hedges have a flat side, like a sloping board, not a curve, and learn to keep that slope even all along the hedge – it is not difficult with a good quality, sharp hedge trimmer.

Keep the Top Narrow

Sloping the sides will naturally keep the top narrow, and that is something to encourage. A narrow top will shed snow and ice better, and the chance of your hedge collapsing is reduced greatly. With a narrow top you can keep it square and flat, if that suits your garden design, although rounding it for a less formal look is even better for shedding snow.

Feed and Water Regularly

Finally, trimming a hedge is like cutting the lawn. You remove material that is part of the strength of the tree, so hedges need more nutrients than untrimmed plants. Have a regular fertilizer program – organic or not, it’s your choice – and water during dry spells. It doesn’t take a lot of time, but that extra care, and the tips we have given, will make your hedge a stand-out feature of your garden.

There is a very good reason that Thuja Green Giant is the top-selling evergreen for hedges and screens – it’s growth rate. Proven in trials to grow faster than any other evergreen, during its early years you can expect growth of 3 feet a year or more, so that solid, tall plants will be yours in just a few short years. But plant growth is complex, and when rapid growth is not seen gardeners are understandably frustrated and look for answers. Let’s examine in detail the different factors that control the growth of those Thuja Green Giants you just planted or are thinking of planting.

Some of the factors that control the growth of plants are a given of their location and can’t really be controlled by us. Let’s start with those, as they alone can often answer the question, “Why aren’t my plants growing faster?”

Climate

Although we rely mostly on the USDA hardiness zones to look at this, these only measure winter low temperatures, and don’t take into account other factors, such as rainfall. How do these things control the growth of your plants?

Low Temperatures

Winter minimums for your zone are averages, and in bad years the real numbers can be much lower. Severe cold snaps kill many plants considered hardy in a zone, while in other, milder years borderline plants thrive. Thuja Green Giant is hardy throughout zone 5, but if there is a severe period of lower temperatures, they can suffer. Foliage may burn, so that plants in spring are now smaller than they were the previous fall. With evergreens, the ability to take up water from the ground all winter long is essential to keeping the foliage green, and especially if plants are new, and a lack of snow cover during a cold spell allows the ground to freeze, then foliage burn can easily follow, even in ‘safe’ zones. If you see dead leaves and burned foliage in spring, then a hard winter is often the simplest explanation.

As well, the amount of sunlight and dry winds in winter are a big factor in foliage burn. Cold dry winds and bright sun will cause damage at temperatures that will be just fine in humid, cloudy conditions.

Dry Summers

If you garden in a zone that typically has hot and dry summers, you will not see the same growth on your plants compared to places where they receive a regular water supply. Even watering cannot completely make up for those periods gardeners often call, ‘growing days’, when gentle rain encourages rapid growth. Only an Arizona-style full irrigation system can produce a lush oasis in hot, dry areas, and that is beyond the reach of most of us. So if growth happens mostly in spring and fall, with a long, dry, dormant summer period, you will not see as much growth on your Thuja Green Giant.

Wind

In exposed, windy places plants naturally respond by hunkering down, and creating broader forms, with shorter extension growth. Although Thuja Green Giant is often used for windbreaks – and it’s a good choice – the growth rate will be slower than in a sheltered area, which encourages the longest stem extension.

Location

Every garden is different, so your Thuja Green Giant plants may not have ended up in the perfect spot for maximum growth. There are two main limitations that can only be fixed in theory, since were we plant is often determined by the layout of our gardens.

Sunlight

Thuja Green Giant grows best and fastest in full sun, yet in gardens many places, including where you want a hedge, may be shaded, at least partly, by trees or buildings. Not only will the growth be slower, it will inevitably also be more open, and creating a dense, solid hedge will be more difficult. Like wind exposure, you can rarely control this, since a hedge has to go where a hedge is needed, so if there are significant periods between early spring and late fall where your hedge is in shade, the growth rate will be reduced.

Competition from Other Plants

While shade from surrounding plants is obvious, their underground activity is not, and we underestimate how far the roots of trees spread. Those planting holes you created, filled with good rich earth and fertilizer, are magnets for surrounding mature plants, which will have their roots into them in a couple of years. Thuja Green Giant will not grow at its maximum rate when it is fighting with tree roots for water and nutrients.

How to Improve the Growth Rate of Your Plants

All the above elements are pretty much out of our control, but there is lots we can do, with a little work, to get the best from our Thuja Green Giant plants, even if there are intrinsic limitations.

Soil Preparation

This is number one. Digging deeply, adding organic material and basic nutrients, as well as started micro-organisms, all give your plants the best possible start. This will be reflected in the speed they grow. Some people are disappointed when they do all this and still see limited growth during the first year after planting. Remember that until they spread out into that inviting soil, your new plants are dependent on the root ball that came out of the pot, so slower growth in the first year is, unfortunately, something we can do little about. The maximum period of growth for newly-planted trees is usually from year 2 to year 5, and it is during those establishment years you will see the biggest changes.

Watering

How, and how often, you water depends on where in the establishment cycle your Thuja Green Giant plants are. During that first year there are two goals. The first, basic one is to keep your plants alive, and that means keeping that root ball moist. A common mistake is to thing that if the soil looks damp everything is good. In reality your trees are at first dependent on that limited volume of root ball, so keep it moist by watering close to the stem.

Equally, you want to encourage your trees to spread their roots outwards, and they will only do that if the surrounding soil is moist. See that as a separate job, and keep the nearby soil damp, especially deeper down. Since a lot of root growth happens in fall, early winter and early spring, watch out for drought at those times, not just during spring and summer.

After that establishment period watering should be deep, and spaced out, so that the ground dries between watering, especially in the top few inches. You want to encourage deep rooting, so moisture needs to be lower down in the ground.

Fertilizer

For maximum growth, regular fertilizer application, either traditional or organic, is needed. This releases nutrients directly around the trees, so they have rapid access to them. In the first two or three years, liquid applications are best, as that really does get them down to the limited root area. After that, granular fertilizers work well, and they are a lot easier to use, especially if you opt for a slow-release type that only needs one application a year.

Many people today want to grow their plants the natural way, without using synthetic chemicals and sprays, to protect themselves, their families, their community and the greater environment from harm. For decades we became so used to growing with fertilizers it can seem it must be hard to do it any other way. It isn’t. Let’s look at how you can grow hedges, screens and evergreen specimens of Thuja Green Giant, or any evergreen, successfully, without resorting to artificial methods using chemicals. Instead you can grow it naturally – the organic way.

The Power of Organic Material

In the natural world there is a great cycle of decay and renewal. Plants and animals begin their lives, grow, and then die. During that life they excrete the things they don’t need. That cycle is part of a great exchange of materials, between the complex chemicals that characterize living things, and the simple chemical elements of the rocks and soil. Between these things are the decomposers – fungi and bacteria that break down complex molecules into their simpler components. They take dead things – leaves, branches, fruits and roots of plants, and the waste from animals – and live on it, and in the process bring back the basic elements other plants need to grow.

We call that broken-down stuff, which still has further to go before it is completely returned to simple minerals, ‘organic material’. This can be garden compost we make ourselves, or that is made on a larger scale from city waste, or it can be the waste from farming. Animal manures from cows, horses and sheep are mixed with straw and turn into organic material. Plus, there are other sources of this valuable stuff, such as seaweed, or the waste left over when the oil is extracted from seeds like corn, soya or sunflowers. Even sawdust, if treated properly, can be used for this purpose.

This organic material is the basis for all organic growing, and fortunately, even if you don’t make your own garden compost, it is readily available in some form or other from garden centers and nurseries. So, if you are starting a hedge or screen with Thuja Green Giant, or if you already have plants you want to grow organically, the first step is to get yourself some.

Organic Material Works Miracles in Your Soil

What is so wonderful about organic material, and what sets it apart from artificial fertilizers is not the elements it contains. Every scientist will tell you – correctly – that the minerals it releases, such as Nitrogen, Potassium, or Iron, are exactly the same to the plant as a box of artificial fertilizer.

No, the secret of organic material lies not in its minerals but in what it does in the soil. Organic fertilizing is about feeding your soil, not your plants. If well-maintained your soil will do the feeding, from the vast mineral reserves locked up inside it. As well, organic material improves the physical structure and properties of your soil, making every soil more suitable for growing.

In clay soils, when we add the coarse pieces of organic material, we open up the structure of the soil, letting air in and water out. The enemies of plants in clay are just that – not enough air, and too much water. Roots need air and when it is excluded by too much water the roots suffer, become prone to disease and die. Clay soils usually have abundant chemical reserves in them, but these cannot be liberated for plants, because the airless, wet environment is unsuitable for the organisms that release them, and for the plant roots to find them. So digging organic material into the soil before planting Thuja Green Giant will open up your clay soil to good growth.

Amazingly, it works just as well in sand. There the problems are the opposite ones. Sandy soils don’t hold enough water for vigorous plant growth, and the rapid movement of water between the coarse soil particles removes nutrient minerals as fast as they are produced. Organic material holds more water, and it also acts as a bank account for minerals. As they are produced they bind to the material, so they are not lost, and the soil becomes richer and more nutritious.

So the practical lesson is, when planting, and as mulch each spring on young plants, organic material of almost any kind is your friend, and the key to growing Thuja Green Giant the natural organic way.

Feeding Young Trees

Now to access all those nutrients plants need an extensive root system. Young plants don’t have that, so they can use a hand to get going. The best way to do that the organic way is to use more concentrated sources of organic material. There are lots of these, but popular and reliable sources include poultry manure, decomposed feathers (rich in nitrogen), bone meal (for phosphorus) and alfalfa meal (another rich but gentle source of nitrogen).

As well, poor soil often lacks those microbes that do the work. These microscopic miracle workers take all that organic material and turn it into mineral elements, as well as releasing materials like gums and resins that bind the soil together into crumbly particles, creating the rich, healthy soil we want. There are several different materials on the market to kick-start both your soil and your plants. One good one is the Bio-Tone range, that includes a great ‘starter plus’ product for planting, which supplements your soil preparation and provides a solid base of microbe activity. This is especially important when you are starting a garden in disturbed soil, perhaps following construction. All that digging and soil moving disturbs the system, which needs to be restored or it can lay barren for a long time.

Once initial establishment is over, switch to a supplementary organic food, like seaweed emulsion, or another product, like Bio-Tone ‘Tree Tone’, which is designed for evergreens and trees, with a good nitrogen level for rapid growth and rich-green foliage.

Green Gardening is not Rocket Science

Growing Thuja Green Giant – or your other evergreens – in a natural, organic way is easy. Take care of your soil, and boost growth with the minerals released by the decomposition of organic materials, and you are there. You preserve the soil environment and improve it for growing plants at the same time. After all, these natural cycles have kept the planet green for millions of years, so harnessing them for our gardens is not rocket science. Good soil preparation and a steady, natural trickle of nutrients is all it takes – enjoy growing green!

Thuja Green Giant is an evergreen conifer, widely planted for hedges and screens. Its vigor and reliability come from its hybrid parentage, marrying the best features of each parent, and masking their limitations.

Let’s look at those parent plants and see what features they have that produced this remarkable plant that has been planted in millions over the last few decades.

The Basic Story

Thuja Green Giant began its life in Denmark, at the Poulsen nursery in Denmark. This family nursery dated back to 1878, and it has once specialized in roses. In 1937 an unusual Thuja plant was found there, but because of the Second World War very little attention was paid to it. In 1967 the National Arboretum in Washington, D.C. bought a shipment of plants from Poulsen, to look for possibly valuable introductions for American gardens. Among that shipment were several Thuja plants, which were put out in a nursery to grow. By the 1990s, one plant was catching the attention of visiting nurserymen who were amazed to see it had grown 30 feet tall in just 25 years. They were given pieces to grow and test, and a nurseryman from Tennessee called Don Shadow suggested the name ‘Green Giant’ for the plant. A major grower – Wayland Gardens – produced many plants, and promoted it as a replacement for older, diseased hedges, and the rest, as they say, is history. But how this plant developed was at first a mystery.

DNA analysis was a new thing in the 1970s, but some scientists from the National Arboretum, The New York Botanical Gardens and the Holden Arboretum took on the challenge, and they found this plant was something that had never happened before – a hybrid between two species of Thuja, one from Japan and one from America. We don’t know how it came about – probably a chance cross-pollination – but the result was a demonstration of something well-known to plant breeders. They call it ‘hybrid vigor’, and it is seen in many of our food crops for example. When two closely-related plants are crossed together the strongest genes dominate, and most of the weaker ones are hidden. As a result, the offspring are far more reliable and vigorous than either parent. But our interest here is in Mom and Dad – the two parent species. Let’s look at them in more detail.

Japanese Arborvitae – Thuja standishii

Known as nezuko (クロベ ) in Japanese, this tree is an important timber tree in Japan. Light and soft, and therefore easy to work by hand, but durable, waterproof and pleasantly scented, it is used for sake kegs, tubs, and other bent-wood items. It is one of the Five Sacred Trees of Kiso, along with Sawara cypress, Hinoki cypress, umbrella pine and Hiba arborvitae. These were, and still are, the trees used to build Shinto shrines, temples and palaces, so for common people cutting one down was punishable by death.

Japanese Arborvitae grows 65 to 100 feet tall in the forests of Japan, with broad trunks up to 18 feet in diameter 4 feet above the ground. The foliage has a pleasant lemony smell, and in appearance it is typical of arborvitae. Only an expert can quickly tell one species of arborvitae from another.

This tree is found in southern Japan, mostly on the islands of Honshu and Shikoku. We might expect it to enjoy hot weather, but in fact it grows only at high altitudes, in mountainous areas up to 8,000 feet high. This means it grows well only in cooler, moist climates, an in North America it grows best in the northwest and northeast. It will not grow in dry areas, and in fact if you wanted to grow one it would be hard to find a plant except in a specialized nursery, or if you grew it from seed. If you live in a part of the country where it will grow, you might be able to find one at a local botanical garden or horticulture school in a college or university.

Western Redcedar – Thuja plicata

Since we don’t know how Thuja Green Giant came about, we don’t know for sure which plant Mom was – the seed parent, and which was Dad – the pollen parent. But it is nice to think that it might have been Western Redcedar, the rugged American meets the Geisha Girl. Sexual stereotypes aside, the American side of this meeting is not such a different plant, although much more widely known to the average American.

Even non-gardeners know the lumber called ‘red cedar’. Waterproof, and so very popular for outdoor construction, it has a well-deserved reputation as the lumber of choice for gardens. It needs no preservatives, and ages gracefully to a soft gray color, while weather brings out the grain in the surface, creating over the years that ‘lived in’ feel to the garden. Don’t confuse it with cheaper white cedar, from eastern arborvitae, Thuja occidentalis. That wood lacks much smell, and it is generally inferior. Red cedar has a very characteristic smell, of spicy decongestant chest rub, from the camphor in it, which fades over time.

Red cedar lumber is cut from the Western Redcedar tree, the other parent of Thuja Green Giant. This is an even taller tree than its Japanese cousin, and old trees approach 200 feet in height, and they can be 1,000 years old. The foliage when crushed smells like pineapple, and it has the same stringy reddish bark as the Japanese Arborvitae. It grows on both sides of the border between Canada and the USA in the northwest, and on Vancouver Island. In the US it grows through Oregon and Washington State. It also grows as a forest tree around the world, from Australia to Hawaii, and in Great Britain it has become a naturalized tree, spreading by itself. It grows along rivers and in the lush forests of those areas, kept constantly moist by rainfall in all seasons.

Like Japanese Arborvitae, you would have to search for a tree to plant, certainly outside of its native states. In Europe and Great Britain it is widely grown, especially for hedges, as the mild, damp climate suits it well.

Thuja Green Giant

So given the parents, both of which thrive only in damp, cool places, it is remarkable what a tough child they had. From zone 5 to zone 9, in a wide range of growing conditions, including drier zones, this reliable plant certainly shows us what hybrid vigor looks like in trees. For consistent rapid growth and reliability, it is still the number one choice almost everywhere.