Fall Trimming of Thuja Green Giant

The Labor Day weekend marks the turning point of the year between summer and fall. September is an important month in the garden, with preparations for the following year on the calendar. Besides planting trees and shrubs, and of course some spring bulbs, a careful and thorough hedge trimming is recommended. You want your Thuja Green Giant hedges to go into winter not only looking good, but with the best chances of coming through the winter in perfect condition. If you only trim once a year, this is the time to do it. With that in mind, let’s look at some suggestions to achieve that perfect trim, and give yourself the best hedge in your neighborhood.

Tips for Fall Hedge Trimming

  • Sharpen Your Trimmer – you will get the perfect cut
  • Slope the Sides – a gentle inward slope keeps growth right to the ground
  • Round the Top – a rounded top will shed snow and ice, preventing breakage
  • Trim the Face in all Directions – don’t encourage long, upward-growing branches
  • Never Cut to a Leafless Branch – new growth can only come from green branches
  • Apply a Fall Fertilizer – this will toughen your plants, and keep them green all winter

Sharpen Your Trimmer

A sharp trimmer makes a clean cut, leaving no ragged edges to turn brown. Although you have to look closely to even see those brown edges, when they are all over your hedge they destroy the lush green look you strive for. Sharp trimmers greatly reduce that browning, as well as making the whole job so much easier.

There are two choices. You can take your trimmer to a professional dealership, preferably for the brand you own, and have your trimmer cleaned, adjusted and sharpened. Since they have sharpening machines, the result will be a trimmer that cuts like the first day you used it.

If you don’t want to do that, or your trimmer is only a little blunted, then you can do the job yourself. First, clean the blades, to remove dirt and dried-on resin and sap. You may need a solvent to do that – alcohol or petrol both work well. Use a brush to loosen the dirt, and rinse off petrol with soapy water. Then you are ready to sharpen.

You need a flat file with a fine grain, and a sharpening stone. Begin by filing the blades. Move the file in the direction of the blade, and keep the same angle as the blade is already sharpened at. Only file areas that already have an edge, and don’t file too much. Do the same amount of filing on each blade – just a few strokes will do it. Now pass the sharpening stone flat across the bottom of the blade, to remove the burr. Brush the teeth with a stiff brush to remove filings, and apply an anti-rust spray. Job done!

Set the Angle of Your Hedge

An important part of creating a durable, long-lived Thuja Green Giant hedge is establishing a gentle slope to the sides. The upper part of a hedge will always grow more vigorously, and eventually starve the lower parts, as well as weakening them from the shade created by the top. To keep your hedge thick and green right to the ground, you need to slope the sides inwards by a few degrees. This doesn’t have to be noticeable, but it should be enough to let the light right down to the bottom. You can use a long pole and a level to visualize an inwards slope, or you can make a wooden triangle, with one side sloping backwards by a few degrees. That will give you a consistent guide, which is very useful for a long hedge. If you can see your hedge from its end, then you will be able to see the angle clearly, and see where you need to trim more.

Round the Top of Your Hedge

While it is possible to maintain a flat top, as long as you keep it narrow, for most hedges it is easiest to shape the top into a semi-circle. This will shed snow effectively, preventing breakage under the weight of snow and ice, something that will quickly destroy a beautiful hedge. Keep the top thin, no more than 12 inches wide, as a thick top is much more likely to lodge snow, and break open. If your top is thin, then you also know that you have got that sloping side right.

You should also try to keep the top level, or if you are on a steep slope, cut into in several sections, with a neat drop in height for each one. Sloping tops just look weird and untidy, and won’t give your garden the quality finish you want.

Trim Your Hedge Horizontally

A big mistake of many novice hedge trimmers is to only use the trimmers going upwards. This encourages long, upright branches on the face of the hedge, rather like a comb-over on a balding head. This might make the hedge look lush, but those long branches are vulnerable to damage, and they are easily loosened by wind and storms. They end up hanging outside the hedge, and often breaking, leaving a large gap that can take several years to fill.

Much better is to pass the trimmers in all directions across the face of the hedge – upwards, downwards and sideways. This will encourage short, horizontal branches, with dense, tufted ends forming the green parts of the hedge. These are much more durable, and if one does die, it doesn’t leave a large hole, but a small one that will fill in a single season or less.

Never Cut into Leafless Branches

Sometimes you see hedges which have clearly not been trimmed for several years. In an attempt to reduce the height or thickness, someone has cut the branches back to bare stumps. Never, ever do this! If you do, those branches will not grow back. Like most evergreens, Thuja Green Giant cannot produce new green growth from a bare stump, only from thinner branches that still have some green, leafy parts to them. This is a good reason to trim your hedge at least once a year, or you will find it very hard to reduce its height of width, and it will soon grow larger than you wanted it to be.

Use a Fall Fertilizer

Ideally, you want your hedge to produce just a little new growth after the final trimming – enough to make it look green and lush, but still neat and tidy. To do this, try to trim about 6 weeks before the temperatures falls below 40 degrees, when most growth stops. When you trim, also apply a fertilizer designed for fall application to hedges. These are usually available in garden centers and stores at this season. They contain higher levels of potassium, which strengthens the cell walls, making them more resistant to cold. This reduces the risk of any winter browning, and also makes stems that are more resistant to being pushed over by wind or storms. As well, some of these fertilizers contain nitrogen in a form that is only released in warm weather. So it sits in the soil until spring, ready to feed the first flush of growth. There will also be a small amount of nitrogen to give a quick flush of new fall growth, making your Thuja Green Giant hedge look green and lush all winter long.