The Vital First Year for Your Hedge

So you planted a hedge last fall, you have just planted one in the last few weeks, or you are about to do it very soon. Congratulations – hopefully you chose something tough and fast-growing, like Thuja Green Giant, or in colder areas, Emerald Green Arborvitae. In very hot, dry areas you perhaps went with Italian Cypress, but whatever you chose, what happens in the first year after planting will set things up for the rest of your hedge’s life. Let’s see what you can do – nothing complex you can be sure – that will give your valuable new hedge the best start in life.

Prepare the Soil Well

If you have already planted your hedge, then this may be advice too late, but if not, then three things are important:

  • Dig Deeply – try to prepare the soil as deeply as possible. Try to go down 12 inches, mixing the soil, and adding suitable materials. For a single tree, prepare an area at least 3 feet across, or a line 3 feet wide for planting a hedge row. If you use a roto tiller, these machines can fool you into thinking you have done a great job, while in fact they just went over the surface. Go over two or three times, working the machine slowly, and letting it sink into the ground as far as it will go.
  • Add Organic Material – it doesn’t matter much what kind, just as long as you add it. A layer 2 to 4 inches deep is usually best, and garden compost, rotted farm manure, rotted leaves, even lawn clippings and fresh weeds, are all good materials to incorporate into the soil. These increase the water-holding capacity of light soils, increase the drainage and air content of heavy ones, and add nutrients and valuable microbes too.
  • Add Phosphates – this nutrient, needed for root growth, doesn’t move into the soil from the surface for many years, so it must be dug in to be effective. Sprinkling it on top after you plant is completely ineffective. You can use bone meal, superphosphate, or triple superphosphate, it really doesn’t matter, so consider cost. Sprinkle a layer over the soil before you add the organic material. You can’t damage your plants if you use too much, and a solid dusting is about right, so that it is clearly visible.

Water Regularly

This is so important, and basic, that it cannot be over-emphasized. New plants only have the soil that was in the pot to depend on, and in warm weather, or when growing vigorously, they soon use that up. It takes some time for roots to move out of this limited space and explore the surrounding soil. So when watering your new hedge, don’t use a spray and water the top only. Use a gently rain head, or a slow-running tap, and soak down close to the stem of each plant, letting the water run deeply down. This will keep your plants happy. You do also need to keep the surrounding soil moist, to tempt the roots to spread out, and this is why many smart gardeners put a ‘leaky pipe’ watering hose – the black, porous kind – down along their hedge. Weave it in and out of the stems, and let it run for a few hours, until the whole area is thoroughly watered. It does a great job, and also saves you the trouble of standing their watering.

Fertilize with Liquid Fertilizers

Feeding hedges is important. Like lawns they get clipped regularly, so foliage is lost, and it has to be replaced. This means more nutrients are used than by an untrimmed plant. Granular fertilizers are the easiest to use, and the most cost-effective, but young plants don’t have big root systems, so they can’t easily access the nutrients from these materials, which need time to migrate down into the soil. Far more effective is a liquid fertilizer, that carries the nutrients right down to the roots with the water. Choose something designed for evergreens, which will have lots of nitrogen to stimulate rapid growth. These fertilizers come as concentrated liquids – the easiest to use – or as a powder – the most economical. The only issue is that because they are dissolved in water, they cannot be very strong, so you need to re-feed every 2 weeks to a month. But for the first year they really make a noticeable difference in the growth rate and foliage density of your new plants, making them sturdy and strong. Stop feeding in early fall, to allow your trees to slow down and toughen up for the coming colder weather.

Start Trimming When Your Start Growing

When creating a hedge, we want a dense, twiggy structure, with lots of tight branching, to give you the solid structure that makes the most private hedge, the best looking one, and the one that resists winter breakage too. The single biggest mistake when people plant new hedges is to let it grow until it reaches the height you want, and then start trimming. This never gives the best structure. Far better is to trim lightly and regularly from day one. As soon as you see new growth, snip off the end inch of it. This will encourage the dense branching you want. It will also allow you to direct the growth upwards, not outwards, so that you have a slip hedge. Don’t forget to keep the upper part narrow, to encourage plenty of growth lower down. Once it gets going, trim very lightly once a month from spring to mid-fall.

Try to keep the front flat, but sloping slightly inwards, and the top horizontal – you might need some strings and a level to get started. Don’t trim at the very end of the season, especially in colder areas, as soft, young growth can suffer winter damage. In the end you won’t reduce the rate of growth significantly, as your new hedge works its way up to your target height, but you will have a great hedge as a reward for that bit of extra work.

How Hardy is Thuja Green Giant?

This might seem like a very easy question to answer – just check the hardiness zone listed for it, put your zip code into the USDA map site, and there is the answer – right? Most sources list zone 5 as the coldest place to grow Thuja Green Giant, which means it is considered hardy to minus 20 degrees Fahrenheit (approximately minus 30 on the Centigrade scale, for all you scientifically-inclined gardeners – odd isn’t it, that we use metric money, but then use an ancient European temperature scale everyone else abandoned many, many years ago?). So that should settle the matter, and there is nothing else to talk about. . .

What About Wind Chill?

At this point someone is going to say that we have forgotten wind chill, that factor that separates two days at the same temperature into ‘tolerable’ and ‘brutal’ because of a howling northerly wind. Wind Chill certainly affects us, but not plants. Why? Because wind chill is a measure of how rapidly heat is drawn away from our bodies, something which happens because we are warm-blooded. Plants, on the other hand, are not, and their internal temperatures are basically the same as the surrounding atmosphere or soil. Apart from a few plants that grow so fast in spring – mostly bulbs – that they actually generate enough heat to melt their way through the snow, all plants are at the same temperature as the air, so Wind Chill is irrelevant to them.

Winter Burn

Wind does affect plants though, and it adds complications to just how hardy a plant can be. The usual advice given to gardeners about growing plants at the limits of their hardiness is to find a ‘sheltered spot’ in the garden for them. This usually means south-facing and protected by hardier plants from cold northern winds. This advice is of limited value, because what evergreens need protection from in winter is dry winds – whatever their temperature and direction. You may have seen the leaves plants in summer shrivel and burn in hot, drying winds, but although direct sun may play a part, it is the dryness of wind that matters. We may feel a hot summer wind as dry or damp, but in winter all winds are relatively dry.

This is because the amount of water the air can hold increases with temperature. Yes, many people don’t realize that a cold winter wind is much, much drier than a balmy summer breeze. For example, at 100 degrees Fahrenheit the air can carry over 50 grams of water in a cubic meter. At 50 degrees that falls to less than 10, and at 32 degrees less than 5. By the time we reach minus 20, the hardiness limit for Thuja Green Giant, it holds just 1 gram of water. Larger amounts turn into dew, mist, fog or rain. Winter air is very, very dry.

How does this effect plants? Water is constantly being lost from the leaves and foliage of plants, by a process called transpiration. That water must be replaced from the roots, and when the ground freezes that cannot happen. So over time the foliage loses more water than it can replace, leading to drying, and the effect we call ‘winter burn’. In evergreens, this is the primary factor controlling hardiness. The other is the ability of roots to resist cold. Since soil is much warmer than the air, roots have much less cold-resistance than stems and branches. This is why plants left in pots outdoors die in winter, but the same plant in the ground will survive perfectly well.

What Does this Mean for Thuja Green Giant?

What all this means in the end is that if you can either increase the ability of the roots to take up more water, and/or reduce the amount of water lost from the leaves, then Thuja Green Giant can resist lower temperatures than usually suggested. Also, if you neglect these factors, it can easily die, even in zone 5. This is true for all plants, but especially for evergreens, which are vulnerable, because they carry their leaves into winter. From a practical point of view, this weakness is going to be worse in younger plants, so if you can keep your plants growing until they reach a good size, they are much more likely to survive in the long-term. So how about some tips for doing that?

Protecting Thuja Green Giant from Winter Cold

There are three ways to protect Thuja Green Giant, and other evergreens, from cold winter temperatures, especially when they are young.

Encourage Deep Root Growth

Deeper soil is warmer and doesn’t freeze. (How deep your soil freezes depends on where you live, of course.) The deeper the roots of your trees go, the more water they can continue to reach in winter, and the less their risk of winter burn. When you prepare the soil for planting, try to dig it as deeply as possible, so that the roots have plenty of soil to grow down into.

Water Your Trees in Late Fall

This is a very effective way to protect against winter damage. Let a hose run gently for several hours over the root zone of your trees, so that the soil is thoroughly wet. Do this as close to freeze-up as you can. Increasing the water content of the soil around the roots does two things. Obviously, it puts more water near the roots, so they can take up plenty. More subtly, it increases the specific heat of the soil, so it takes more winter cold to make it freeze. Specific heat is the amount of energy needed to change the temperature of something. It takes five times as much heat to warm wet soil as against dry soil. so that when the cold penetrates, we can think of it as being ‘used up’ in the top few inches, instead of freezing down a foot or two. The deeper roots can still get at liquid water and keep the foliage moist.

Mulch your trees

Besides its other properties, mulch is a good insulator. Soil covered with mulch, especially plant-based mulches, not stones, will freeze much less, and often not at all. Once you have completed that late-season watering, mulch around your trees too.

Use Anti-desiccant Spray

Widely used by professionals, but neglected by home gardeners, these products, which are entirely natural and made from an extract of pine trees, cover the foliage with a protective coating that reduces dramatically the rate of water loss. They have an equally dramatic effect on survival, especially helpful with new planting, and reduce or often eliminate winter burn, even on vulnerable plants at the limits of their hardiness.

So How Hardy is Thuja Green Giant?

You can see the picture is complex. The bottom line is that if you help your young trees in the ways suggested here, their survival is going to be greatly improved. In zone 5, and even into zone 4, your trees will leave winter as healthy as they entered it, and you can push the hardiness significantly – this is indeed a tough plant.

Start Up Your Hedge for Spring

After a hard winter, it time to get out and explore the garden, to see how it survived, and if anything is needed. For hedges in particular, winter can be tough, especially if there has been heavy snow, freezing rain, or storms. As well, there are things to do that will give you the best results in the coming growing season, so let’s look at some things you can do that will fire up your hedge for a great season of growth and development. These things are especially important if you planted a hedge last year, in spring or in fall.

Check for Broken Branches

The weight of snow, ice, or simply strong winds can all break branches, especially on older hedges that have perhaps not been trimmed correctly. They may not always be obvious, although of course sometimes they are all too obvious!  The main issue when removing broken branches from evergreens is that most conifer evergreens, like Thuja Green Giant, Emerald Green Arborvitae, Cypress, and others similar plants, is that they cannot regenerate from old wood. That is, branches that don’t have some green shoots on them. So hopefully leaving a thick branch, thinking it will re-sprout, as most trees do, is never going to work. If a breakage has happened below the green parts of the tree, then remove it neatly right back to the main limb it is growing from.

When cutting, leave the collar of bark you will see just where the branch joins on – don’t cut flush. The cut will be bigger with a flush-cut, and take longer to grow bark over, but more importantly, it is likely to cause die-back into the stem and leave permanent damage and weakness. This, by the way, applies to all limb removal from every kind of tree or shrub.

When you have cut away all the damaged parts you can assess your hedge. If you trimmed from an early age you should have lots of branches surrounding the gaping hole where that limb came out, and you will be surprised how quickly even large holes fill in. Smaller gaps will be gone in half a season, larger ones might take two seasons, but go they will.

If however the damage is to the end of a hedge – perhaps a snow-plough ran into it, for example – it is much harder to repair, and there it makes much more sense to take out the last tree entirely, dig the area well, and plant a good-sized replacement.

Mulch Your Hedge

If your hedge is young, or old and showing yellowing and slow growth, then mulch is very beneficial. Use something rich and nutritious, like garden compost or rotted animal manures (cow, sheep or horse) rather than bark chips or shredded bark. Yes, those hard materials last a long time, and they do conserve water and suppress weeds, but they don’t supply any nutrients. Richer organic materials release lots of nutrients as they break down, and for an older hedge they really will rejuvenate it over a few months. For young hedges too, the benefits are terrific, with better soil properties, more beneficial microbial activity in your soil, and nutrients too.

When mulching, keep the material clear of the stems, and don’t bury the foliage either, as it will soon die and brown if it isn’t exposed to light. A layer 2 to 4 inches deep in about right. You don’t need to remove all the old leaves and clippings which often accumulate under hedges, as they will also break down once you had some rich compost.

Fertilize Your Hedge

By far the most important thing to do in spring, especially for a young hedge, is to fertilize it. You can find both older-style chemical fertilizers, and organic-style ones too, and organic ones are especially useful for poorer soils, and of course they don’t involve energy-intensive manufacturing from fossil fuels either. To the plant it makes no difference – by the time they are ready to be absorbed by the roots they have been turned into basic elemental forms – plants don’t absorb vitamins or other complex molecules, since they make them all themselves.

There are three main kinds of fertilizers suitable for hedges – liquid fertilizer, granular fertilizers, and slow-release fertilizers. All three have their uses. Immediately after planting, and for the first season, you will get the best results using liquid fertilizers. These are sold either as concentrated liquids, or powders. Powders are much more economical, and easy to use – just dissolve the recommended amount in water. Young plants have limited root systems, and liquid fertilizers flow right down into the root ball, so they are easily and quickly absorbed, but they need regular application – once a month or even once every two weeks – for best results, as they cannot be concentrated, or the roots will burn.

In the longer term applying liquid fertilizers takes too much time, so after the first season or two, switch to granular forms. These are also more economical. The ordinary types are applied in early spring, mid-summer and early fall. Follow the directions for the amount to apply. Slow-release forms, which look like tiny pebbles, are more expensive, but they only need to be put down once a year. Choose which to use depending on your budget and how much time you have available. Fertilizer in sticks which you drive into the ground is usually not ideal, as it may burn the roots near it, and not spread well to areas further away, producing uneven growth.

Formulations

The fertilizer market is crowded, with many brands all competing for our attention. Forget all that, and instead go straight to the fertilizer formula – the 3 numbers (20-20-20, for example) required by law to be somewhere on the box or bag. If the first number is noticeably bigger than the next two, then that will be fine for a hedge. Even lawn food works on a hedge, although it is not ideal, since it has too much nitrogen (the first number) and not enough of the other nutrients. You want something balanced, but with more nitrogen than anything else. Other nutrients are optional extras, unless you have very sandy soil, where micronutrients can be scarce. If you mulch with that rich organic material we mentioned, then all you need is the nitrogen boost for rapid growth, so don’t worry about the fancy stuff. Check out our blog pages for more detailed blogs on fertilizing hedges.

Watering

In some areas early spring can be dry, with little rain. If that is happening, don’t forget to water your hedge deeply, especially a young hedge. A lot of the annual growth takes place in spring and early summer, and dryness will seriously reduce that, so don’t forget to water.

How to Plant Thuja Green Giant

With spring arriving across the country – sooner in some places than others – planting time has arrived, and many people will be planting hedges and specimens of America’s most popular evergreen, Thuja Green Giant. This fast-growing tree is the top choice for taller hedges and screening, but when faced with that shipment of plant, sitting in their pots, some new gardeners may not be too clear on the best way to plant them, so let’s consider that. After all, getting plants off to a good start is always the first secret of success, and equally, a bad start can set you up for poor results, and even failure.

Prepare the Ground

Although we don’t see it, the life of plants below the ground is at least at important to them as what goes on above ground. Scientists have laboriously excavated the root-systems of plants from grasses to big trees, and in every case the roots occupy a vastly bigger volume than the above-ground parts. Many times bigger. So it follows that we should give it just as much attention, since we want to see much faster growth than a tree is nature will achieve. Most young seedling trees sprouting in the wild die, and those that don’t usually struggle for years to gain a foothold, but in gardens we want rapid growth and establishment from Day One. To do it properly you need two things when preparing the soil for your Thuja Green Giant plants – organic material and a source of phosphates.

Organic material

The exact type you use is not so important, but adding it is. No matter if your soil is sandy, clay, or something in between, the magic of organic material always improves any soil. Sandy soils retain more moisture and nutrients, and clay soils (which usually have lots of nutrients already) develop better drainage and more vital air penetration into the soil. You can use garden compost if you have it, rotted leaves, old potting soil from planters, rotted farm or stable manure, or even peat moss (which despite its popularity is not such a good choice). If you are planting a single tree, you need about a bucket full, and if it is a row for a hedge, you need a layer 2 or 3 inches deep, over an area 3 feet wide.

Phosphate

Of the three major plant nutrients (nitrogen, phosphate, and potash) you only need to add phosphate when preparing the ground. Why? Because this nutrient doesn’t move around in the ground easily, so if you sprinkle it on top it will quite literally take years and years to work its way down to where the roots are. All other nutrients are quickly carried down into the soil by watering or by rain.

There are several good sources of this, and most gardeners know bone meal. Expensive for a big job, its great for a couple of trees. Otherwise track down some superphosphate (or triple superphosphate, which is a bit stronger) and use that – it does the job at lower cost. A heavy sprinkling of this – like a light snowfall – should go down before digging, and in poor soil as some more as you go too. You can’t hurt your plants with too much, and it stays in the ground for many years.

Digging

Scatter the phosphates and then spread the organic material on the ground before digging or rototilling, which should then be done as deeply as you can go. For a row, prepare a strip at least 3 feet wide, or 5 feet wide if you are planting a double row. For an individual plant, dig an area at least 3 times the width of the pot, and again, go deep. Then level of the surface and leave it to settle for a few days before planting, if you can. If it was dry when you dug, setting up a sprinkler and giving the area a thorough watering is also a good thing to do.

Planting

Now to get down to the real job. The night before you plant, give the trees in their containers a good watering, soaking the soil. Never plant a dry tree, because it can be hard to get the root-ball wet after planting is over. Doing it the night before will mean it is not soggy on the day, and easier to handle than a freshly-watered tree.

You will have worked out the spacing for your plants, as we went into in detail in this previous blog, so set out your plants according to your plan. With hedges and screens, the best future look requires careful, even spacing, so put some time into adjusting this until you are satisfied. Use a stretched string to get the row straight.

If you have prepared the planting spot well you will only need to dig holes a little wider than the pot – just enough to be able to easily plant. Dig the holes where you have placed each plant, to the same depth as the pot only. Leave the tree standing next to each hole.

Preparing the Root Ball

Some people find the next step surprising, and hesitate to do it, because they are fearful of damaging the plant. Don’t be. This is an important step in helping your trees become established quickly and preventing future problems with roots strangling the growing trunk of your trees – a problem called ‘girdling’. It is similar to what you may have seen with trees tied to tightly to a pole – the rope cuts into the bark, and it can kill the tree. Roots wrapped around inside the pot can do the same thing as they and the trunk grow larger. Preventing this is important, so don’t be afraid for the tree.

Slide your Thuja Green Giant out of the pot. Take a sharp box-cutter and make 3 or 4 deep cuts from top to bottom around the root ball, going in about one inch deep. This will cut through the girdling roots.

Into the Ground

Now it is time to finish, and this is the easy bit. Sit the tree in the hole. Use a short stick laid across the top of the hole to adjust the position so that the top of the soil in the pot is level with the soil surface. Don’t bury deeply, and if your ground is poorly-drained, raise it up an inch or two above ground level. Now push back some soil, and using your foot, firm it down around the roots. Once you have about two-thirds of the soil back, fill the hole to the top with water. While it drains down, move on to the next tree. Once the water has drained away, put back the rest of the soil, firming it gently down. Rack the surface level, and you are done – no need to add more water, although if you want to you can.

To finish, mulch over the root balls with an inch or two or organic material, keeping it away from the trunk and foliage.

That’s it! You have given your Thuja Green Giant trees the best possible start for their life in your garden.