Trimming Your Thuja Green Giant Hedge


Thuja Green Giant makes a perfect hedge – dense, upright and always green and healthy. It is fast growing, so you will soon have the screening and backdrop for your garden that you are looking for. Taking some simple steps in trimming it properly will help you grow a hedge that will not only look good, but will also be healthy, strong, and resistant to snow and storms. With a little care your hedge will always be green and dense right to the ground – just like you wanted it to be.

Start Trimming Soon After Planting

The commonest mistake made with hedges is to wait until they reach the height you want and then start trimming. This approach will never give you a strong dense hedge, so instead you need to start early. As soon as your new plants are established – and you can tell that by the appearance of new growth – you should start trimming them very lightly. At first, you just need to go along the line and snip off an inch or two or the longer new shoots. This will encourage your plants to send out more side-shoots, and develop a denser pattern of growth. Allow the hedge to grow a little, and then trim lightly again. Gradually let it grow to the size you want, and it will already be neat and dense when it gets there.

When to Trim Thuja Green Giant

You can trim your hedge at most times of year, but the best times are late summer to early fall, or late spring, after the new growth has sprouted out and ripened. You may need to trim at both times if your hedge is young and growing vigorously. If you want a very neat hedge at all times, then you can also trim in summer, but do it before the hottest part of the year begins. If you live in a warm area with mild winters, then you can trim just about any time, although you should still avoid the heat of summer and the coldest part of winter.

Slope the Sides

For green parts of plants to grow, they need sunshine and light. If the top of your hedge is wide, then the lower parts will get less light, and become woody and twiggy, with little or no green shoots. So right from the start you should slope the sides inwards by a few degrees so that the top is thinner than the bottom. Imagine that you laid a long pole against the hedge, leaning inwards slightly. All the shoots that stick above that pole need to be cut off, so that you have a flat surface that leans in by maybe five degrees. A common mistake is to make the sides vertical, and then just taper the last foot or two. This is wrong – the whole side should slope, right from the ground.

If you grow your hedge in this way, it will have healthy green growth right to the ground for the longest possible time. It also means that with a thinner top and with sloping sides snow and ice will fall off easily, not build up on the top and break the hedge. If you do this you not only keep your hedge healthy and green right to the ground, you protect it against snow breakage too.

Trim Your Hedge the Right Way

When you do the actual trimming, keep the shoots horizontal. This means stopping them from growing as long, upward shoots on the outside of the hedge. Aim for a brush-cut, not a comb-over! These long shoots can easily become dislodged, or break under snow, and if they break or die they can leave a large hole that will take a long time to fill back in.

Trim from side to side and even down from top to bottom – not just up from bottom to top. This will prevent long shoots developing and give your hedge a dense, full surface. Start trimming at one end, and start trim from the bottom up. There will be less growth at the bottom to cut off, so that sets the base of the slope you are going to create. As you trim higher up, you will notice that to keep the slope even you are cutting off longer shoots and more of the hedge. This is normal and correct. The upper growth is always more vigorous and by removing more you will prevent it from drawing food and water away from the bottom. This, and letting the light in, is how you keep the bottom thick and healthy.

If you planted your hedge along a path or driveway, you already have a line to follow to keep it level. If it doesn’t, then especially while you are training it, a tight string stretched from one end to the other along the ground makes a good guide for you to. Work steadily along, trimming all the way to the top in each section, but don’t trim the top flat yet.

Once you have a nice even slope, and a flat surface all along the hedge you can think about the top. Thuja Green Giant can be trimmed square or rounded, it is your choice, but a rounded trim will shed snow better if you live in an area with heavy winter storms. Use a long pole with a mark on it leaning against the hedge to show you the height, so that you get an even, level top – it looks so much better that way!

It is important to realize that only stems with green growth on them will send out new shoots. Never cut into a branch so hard that it is just a bare stem. These will never sprout again. This is another reason to start trimming early in the life of your hedge, because If you let it become overgrown, it will be hard or even impossible to get it back to size, without leaving bare stumps that will never grow.


So start trimming early in the life of your hedge, and trim regularly, at least once a year. This way you will have a neat, dense, healthy and beautiful hedge for many years to come.