Monthly Archives: July 2018

A lot of the focus with caring for Thuja Green Giant is on the actual planting and establishment of new plants. This is important, because good establishment means durable plantings and a long life for your bushes. But after a few years your hedge, screen or specimen plants will be established in your garden, and questions come up about caring for these older plants. So in this blog we are going to focus on that – what special care and steps are best for older plants, particularly so that they go on to have a long, healthy life, and continue to play their vital role in your garden for years and decades to come.


It is obvious that newly-planted bushes need extra water until they settle in and send out their roots into the surrounding earth. But how long should this go on? What should we do for established plants if a long drought period arrives?

You should continue with watering new plantings throughout their first growing season. So if you planted in spring or early summer, it is best to water deeply once a week until the cold weather arrives, and winter rain or snow takes over. In the following year you should only need to water if there is a drought of three weeks, but if you have very sandy soil it pays to water regularly – perhaps every two weeks, for that second season. In later years you only need to think about watering if there has been no rain for a least a month, and in many soils your Thuja Green Giant plants will be unaffected by drought periods much longer than that.

The critical season for watering established plants is spring, not summer. Spring is when the major growth push takes place, and that is when the plants need plenty of water. So a spring drought can be damaging – although probably not fata – even to established plants. The new growth will be reduced, it will be thinner and not so green, and repeated over several years, the result will be a thinner plant. So if the weather turns dry in spring, as it so often can, a thorough soaking of your established plants will make sure they perform at their peak best.

Mulching also helps, and with hedges and screens leaving at least some of the clippings under the hedge is the easiest way to create a natural mulch for your plants. That layer of dead leaves will conserve moisture by reducing evaporation from the soil surface, as well as inhibiting weed growth. If you keep your hedge green right to the ground, then those clippings won’t show, and you save time by just blowing or brushing them underneath, instead of having to collect them up.


Young plants always perform best with a regular fertilizer program, but after a few years it can become less important. If your natural soil is a loam or clay soil, it will almost certainly have good natural levels of plant nutrients, and most plants will grow well in it without any assistance. If you have a sandier soil this is not true, and if that sounds like your soil situation, a fertilizer program should be kept up indefinitely. For established plants granular fertilizers, and slow-release fertilizer are best. These require fewer applications a year, and slow-release forms usually need just one spring application, saving you a lot of gardening time. Compare that to liquid fertilizers, which need applying every two to four weeks throughout the growing season – this can become a real chore, especially over the years.

It is usually best to keep up annual fertilizer application even if you have good soil, when growing a hedge of Thuja Green Giant. Trimming removes nutrients that would naturally be re-cycled within the plant, so these need to be replaced for optimum growth. This is also another good reason to spread your clippings underneath your hedge, rather than throwing them away, as their gradual decay will eventually return the nutrients in them to the roots. Evergreen clippings are generally not good in a compost heap, so leaving them in place is the best and easiest way to dispose of them.

In summary, keep fertilizing your evergreens indefinitely if you trim them more than once a year or more, and in all situations if your soil is sandy. For plants left to grow naturally, keeping up fertilizer application is less important on most soils.


If you have Thuja Green Giant, you probably decided when planting if you were going to trim them or not. Some people do underestimate the final size of this big plant, and trimming can become a necessity. If you suddenly see that your plants are too big, don’t rush out and cut them back hard. Like most evergreens, you cannot cut a branch back below where it has green shoots, and have it sprout back. If you get carried away and trim too hard you may destroy your hedge. If it really has become way too big, take back as much as you can, being sure to leave some green growth on every branch. After a year or so it will thicken up, and you can usually go back and get it even smaller than the first time. Better to take your time than destroy those old, established plants.

Even better is to anticipate a plant that is about to become too big, and trim it before, not after, that happens. It is much easier that way, and you will never have to trim so hard that your plants look bad for months, before filling out again.

With a hedge you should have trimmed regularly from an early age, but as your hedge matures it pays to anticipate problems. Keep those sides sloping inwards a little, so that the lower part stays green and thick, and if you live in an area with snow or ice storms, round off the top, keeping it as thin as you can, or the accumulation of ice and snow will break the top and open your hedge out. Watch for sections that seem to be yellowing, as branches can sometimes die back naturally. If you see this beginning, trim back those weak areas while they are still green, so that the surrounding foliage can spread into them. That way, if and when the weak branch dies completely, you will have a much smaller gap to fill in, and you will avoid the eye-sore of a gaping hole for several years. Sometimes too, trimming back an area that is weak will rejuvenate it.

Thuja Green Giant will live for many years, stretching into decades, and it can be maintained as a screen or hedge more or less indefinitely. The secret is to adjust your care techniques as they age, so you avoid problems down the road.

Screening is often high on the list of garden projects for many people, especially if you live in a built-up area. Evergreen screening is an effective and low-cost way to screen out unwanted noise, an ugly view, or neighbors, especially if you need screening above 6 feet. Tall fences are expensive, difficult to erect, and are often prohibited by city by-laws, but planting is not. You can put in screening plants that will grow pretty much as tall as you want, and a popular choice for that is Thuja Green Giant. There are lots of good reasons for this – perhaps the most obvious is the rate of growth – so let’s consider this choice in more detail, to see if it’s the right one for you.

Do You Have Enough Room?

Thuja Green Giant will grow, if unclipped, to a height of about 30 feet, and while that might take 30 years, it will be half that height in as little as 10 or 12 years. The bigger trees get, especially in a long screen, the more difficult and expensive it is to trim them, so the first thing to think about is the effect of planting a green wall, 20 feet or more in height? What about light into your home and garden? That will depend a lot on how close to your home the screen is going to be, and of course whether it is to the north or south, or some other compass position. Tall plantings to the north side will not cast a shadow, while in other positions it will. Consider too that the shadow will be longest in winter, because the sun is lower in the sky, and that may be just when you want that extra light.

Remember too that Thuja Green Giant will be up to 12 feet wide in time, again if left untrimmed, so consider how much ground space that is going to take up. Depending on your particular situation you could trim up the lower several feet, as they grow, creating trunks on your screen, which will free up ground-level space, but even then you should plant 6 feet or more from your property line, so that the trees are actually ‘yours’ completely.

For many medium to large-sized gardens, that kind of space is not an issue, but in a smaller garden you might want to consider something smaller, such as Emerald Green Arborvitae, which only grows to about 12 feet tall. It is hardy all the way from zone 2 to zone 7, making it the perfect choice for a smaller screen in colder areas.

How Fast Will They Grow?

Here we get into the reason for the enormous popularity of Thuja Green Giant – its growth rate. Young plants can add 3 feet a year – and even more sometimes. As they mature the growth does slow down, but still exceeds a foot a year. This can be seen with the original planting, where a plant at the National Arboretum in Washington reached 30 feet in 25 years. Tiny plants have been proven in trials to reach 10 feet in 7 years, faster than any other evergreen around.

Good soil preparation and a regular fertilizer program will give your plants the best start and the quickest growth rate, so go that extra distance and reap the rewards.

How Far Apart should I Plant?

Given how big Thuja Green Giant gets, you don’t need a lot of plants to make a screen. Depending on how quickly you want that screen to develop fully, you should plant 5 feet apart for a quick screen, and as much as 10 feet apart for something less solid, that will give the effect of screening without making a solid wall of green. If you do want solid, and you have enough room, then plant a double row. Allow 5 feet between the rows, and plant 8 feet apart in each row for a quicker screen, or up to 12 feet apart for something looser. Stagger the planting in each row, so that one plant stands in the middle of the gap in the other row, creating a tight zig-zag.

What About After-care?

Since Thuja Green Giant is not eaten by deer – at least not usually – and has no significant pests or diseases, there is nothing to do in that direction. The most important care is watering during the first growing season, which should be once a week. Don’t rely on showers or thunderstorms, as most of that water only wets the top inch or two in summer. Instead go for a deep soak from a gently-running hose on each plant, or by installing trickle pipe along the line. It’s important to keep the soil further away from each tree moist too, because you want to encourage the roots to grow outwards into a large volume of soil. That will happen much more if the ground around is temptingly moist, rather than dry.

After that vital first year you don’t need to give so much attention to your trees. Watch for dry periods in the second and third years and give those deep soaks again if the soil is dry below the top few inches. A quick dig around with a spade will show you that – just turn up a few inches of soil and feel for moisture. Increased watering during the early years will also accelerate growth, especially if combined with a fertilizer program.

In the early years liquid fertilizer is best – it gets straight to the roots and is taken up quickly. Feed each month for the best results, and that can be a little time-consuming, so after two or three years switch to slow-release granular fertilizers that only need one application a year, in spring. Choose a blend suitable for evergreens and look for Iron and Magnesium in the added micronutrients listed on the label. They will keep your screen a rich green color all year round.

Should I Trim?

Thuja Green Giant produces a dense plant without trimming, but as the early growth is fast and so more open, a light trim each year while the plants are small enough to reach will make it thicker much more quickly. You only need to take off an inch or two, so it has no real effect on the size or rate of growth, but it certainly makes for a dense screen early on.


Thuja Green Giant is the number one choice across much of the country, and it is probably the best choice for you too, but it pays to think it through first. Hopefully these notes will help you reach the right decision.

Hedge trimming season is well underway across the country, and after the rush of spring growth, if you haven’t trimmed your hedges yet, or if you did it a while back, now is the perfect time to do it. There is no doubt that the best way to have good hedges is to trim regularly, and the more you cut, the denser your hedges become. Everyone loves the look of freshly-trimmed hedges, so here are some tips on how to achieve that perfect look and keep your hedges healthy too.

  • Keep your trimmers sharp – sharp tools give a clean trim
  • Choose the right tools for the job – your trimmers should match the scale of the job
  • Trim regularly – little and often to develop a strong branching structure
  • Cut in all directions – branches should be horizontal, not run upwards for several feet
  • Slope the sides inwards – the bottom needs light to stay green and thick
  • Start trimming early – trimming a new hedge right from the start is the way to go
  • Never cut below the foliage – many evergreens can’t sprout from bare wood
  • Have a fertilizer program – hedges need regular feeding to keep growing strongly
  • Water before trimming – don’t trim a hedge during a drought without watering first
  • Stay safe – your personal safety with tools and ladders is always your top priority

Keep your trimmers sharp

That look of a smooth, green hedge is the result of clean cuts to the foliage. Ragged cuts turn brown, so your whole hedge looks brown and dull. Blunt trimmers – hand or power – are the most common cause of poor results, and they also slow you down, meaning multiple passes are needed, where a sharp trimmer would cut in one go. Although it’s possible to sharpen them yourself, most of us choose to have a professional do it. Have your trimmers sharpened before the first cut of the season, and if you have a lot of trimming, or do it frequently, you might need a second sharpen in the middle of the season.

Choose the right tools for the job

Trimmers come in many sizes, and the most common error is using a short bar for a large hedge. A long bar not only speeds up trimming, it makes it so much easier to achieve a flat surface. As well, decide what power-source to us. There is a big move today towards cordless electric, and with the new, lighter, quick-charging batteries, it makes a lot of sense. Freed from the hanging cord, and not surrounded by gasoline fumes, trimming becomes a much more pleasant experience. The result? You are more likely to trim more frequently, with improved results.

Trim regularly

The more often you trim, the denser and more durable your hedge will be. This is especially important with a young hedge – more on this later – but even for a mature hedge trimming twice a year, rather than the more common annual trim, makes an enormous difference. Three trims per year will really give you that top-quality look, if you can find the time.

Cut in all directions

The biggest mistake of a beginner when trimming their hedges is to run the trimmer in just one direction – usually upwards. This seems to be ‘natural’, but it causes long-term problems. You end up with a hedge that consists of long, upright branches, with foliage on the outside only. These easily break under snow or in strong winds, leaving big gaps that are hard to fill. A much better technique is to trim in all directions from day one. Upwards, downwards, and sideways too. By doing this you build a hedge with many more-or-less horizontal branches, with dense, twiggy ends that make the face of the hedge. They can’t be dislodged from the hedge, so it is so much stronger, and if one dies, it only leaves a small hole, that rapidly fills in from the surrounding branches.

Slope the sides inwards

To keep the lower part of your hedge healthy and green, it needs light, and it needs reduced competition from higher up. So your hedge should always be wider at the bottom than the top. Light reaches right down, and the bottom gets its share of food and nutrients. If you let the top grow fat the bottom will soon die, leaving you with a hedge that is full of gaps just where you see it most.

Start trimming early

A lot of people wait until their new hedge plants reach the final size they have in mind – 8 feet tall for example, and only then begin to trim.  If you do this you will always have a thin hedge, because there will be too few branches available to make that solid face. So begin early – as soon as you start to see new growth after planting – and trim an inch or two from the top and upper sides regularly. Don’t be afraid this will slow down growth significantly. It won’t, and your hedge will be so much better for it.

Never cut below the foliage

Another good reason to trim regularly is because hard cutting of most conifer evergreens doesn’t work. If you trim a branch below the point where it has green foliage, it won’t re-sprout at all and that branch will never grow again. Some plants are an exception to this, particularly yew trees, which will come back happily even from thick branches. But for cedar and cypress you can only remove a certain amount of growth – that why it can be better to replace a badly overgrown hedge, rather than attempt to salvage it.

Have a fertilizer program

Regular trimming removes green foliage, so to produce more your hedge plants have to grow more leaves. To do this quickly, and remain vigorous year after year, it pays to have a regular fertilizer program that you follow pretty closely. Use a method that suits your hedge – liquid feed when young, granular when older. Slow-release forms cost more but they save a lot of time, since most only need to be applied once a year. Choose a quality blend that is designed specifically for evergreen hedges, as it has the right balance of nutrients.

Water before trimming

Trimming during drought periods can be risky, as the sudden exposure of all those cut edges can cause desiccation and die-back. But sometimes we just have to do a job when we have the time to do it, and a long delay may leave hedges ragged and untidy. So if you have to trim when the ground is very dry, soak your hedge a couple of days before hand, so that the foliage is full of water. It will trim better too.

Stay safe

After all that, you want to come down from that ladder in one piece. So wear gloves to protect your hands, a hard-hat if you are up a ladder to any significant height. Make sure you have trimmers that have up-to-date safety features that protect you from injury, and if the weather is hot, make sure you stay hydrated.

Spring and early summer are peak times for plants to grow. Some plants only grow at that time and spend the rest of their time maturing buds for the following year. Others grow continuously, but more slowly and less vigorously, outside of that early peak period. When we grow plants in our gardens we often want to have maximum growth, so our screens and hedges mature rapidly, and so our gardens look full and lush. This means that even if we take good care of our soil, so that most of our plants need nothing more, in a few parts of the garden we want to boost growth with something extra.

Supplementary fertilizer is especially useful with plants where we take something away from the plant regularly. This could be fruit or flowers, but it also applies to lawns and hedges. Whenever we clip plants they need extra food to make up for that, and to replace it with new growth. This is where fertilizers come it – to give that extra fillip to those plants we stress by harvesting – even if that ‘harvest’ is just a bag of hedge clippings.

Evergreen bushes in particular – both broad-leaf and conifers – need a particular balance of fertilizer elements, so when you go to the store for hedge food, you see that the makers have created something the call ‘evergreen food’, or something similar. So what is special about the needs of evergreens, and what is in that bag? Why should you buy this one, and not something else? These are all good questions, and ones that lots of gardeners ask, so let’s try and answer them.

Young growth needs Nitrogen

By law, fertilizer bags are labelled with the amount of the three essential plant nutrients in them. This ‘fertilizer ratio’ is the three numbers you will find somewhere on the labelling, that looks like ’18-5-11’, or some other set of three numbers. First of all, you will see that it doesn’t add up to 100%. That doesn’t mean the rest of the bag is ‘filler’, as some people believe. Those numbers are the pure elements, and the rest of the bag is the other elements that are bound up with them to create the specific compounds used. Take a look at the ratio on a bag of evergreen fertilizer, and you will always see that the first number is the biggest. This is nitrogen, the element that plants need to make proteins and DNA, and especially the pigment called chlorophyll, which is the magic chemical plants use to trap energy from sunlight, and then turn it into sugars for growth. Right at the heart of every chlorophyll molecule are nitrogen atoms, and since green plants have lots of chlorophyll, they need lots of nitrogen to make it all.

All those clippings from your evergreens that you rake up or blow under the hedge are green, so you are taking chlorophyll away from the plant, and with it the nitrogen needed to make more. It’s that simple. Of course the plant also needs nitrogen for the structural proteins in its growth too, but chlorophyll is the big user, and so plants lacking in nitrogen will have pale green or yellowish leaves, instead of the rich, deep-green foliage we admire – and want.

In artificial fertilizers that first number is often big – between 7 and 20, depending on the formulation. If you look at organic fertilizers, it is rarely more than 4. That doesn’t mean these fertilizers are weaker, it is instead a result of the measuring system. That number is the amount of nitrogen in a form that the plant can use immediately. Much of the nitrogen in organic fertilizers is locked up in the material, and it takes the activity of bacteria and soil organisms to release it. This is why the top manufacturers of organic fertilizers are adding those special organisms to their fertilizer, to guarantee that all the goodness will be released. It’s a useful extra, especially in poor soils.

Potash is good too. . .

The third number in the formula is potash, and especially if you live in an area with colder winters, higher levels of that nutrient are very useful, as they make your evergreens more resistant to low temperatures. This is because potash (or potassium as it should be called) raises the pressure of the sap inside the cells, making the walls grow thicker and tougher, and so better able to resist low those icy days. It also makes them more resistant to pests, so its always good to see a higher level. If you are trying to choose one food over another, it makes sense to go for higher potash, if everything else is similar.

What else to look for?

You might wonder why some bags of fertilizer are more expensive than others. There are a couple of possible answers – for example it could be that one is slow-release, saving you going out and applying it several times – but another common reason is that some contain micro-nutrients as well as the ‘big three’. These are especially important to get top rates of growth, especially in evergreens that you are clipping regularly.

The most important ones to look for are iron and magnesium. These will be listed lower down and they must be shown on the bag if they are there. Both of them are involved in that chlorophyll molecule again – so vital for good growth. Iron is part of the enzyme system that makes chlorophyll – so low levels mean the factory slows down, and production falls below the necessary levels for top growth. Magnesium is right inside the chlorophyll molecule itself – surrounded by that nitrogen already mentioned – so it’s a raw material, and without enough, again, production will have to fall if the supply chain is disrupted.

Finally. . .

That’s it really. When checking the bag, look for a high first number – nitrogen – or if the material is organic, look for microbes to help release it. Also check if it contains iron and magnesium, and a higher potash number (the third one) helps too. All the rest is window dressing, but now you can make the best choices, and give your evergreens the best possible care.