Thuja Green Giant is a very popular hedging plant, partly for its amazingly rapid growth, but also for it hardiness and how easy it is to make great hedges and screens with this terrific plant. Once your hedge is growing strongly – and that won’t take long – it’s time to settle into some long-term care, and that is where some gardeners need a hand in doing things right. If you make mistakes – and we all can – then you might end up with a hedge that is less than you dreamed about.
There is one problem that we see quite often on older hedges, after the first 5 or so years of regular trimming. The lower part of the hedge has started to thin out, and all the growth is at the top. Gradually the lowest branches die, causing bare spots to develop, and they just don’t seem to re-sprout. Eventually you end up with a hedge that has a couple of feet of bare trunk along the bottom, even though the upper parts are green and healthy. Gardeners often ask why this has happened, and the reason is usually the same – poor trimming habits. There is not much that can be done to bring back that growth once it goes, so if you want the maximum life from your hedges, trimming properly from the start is the secret. Let’s look at the commonest reasons why Thuja hedges become thin and bare at the bottom. The good news is, it doesn’t have to happen to you if you follow a few simple rules.
Plant Far Enough Apart
This is essential when you plant your hedge. Some people are so anxious for a solid hedge they pack the plants root-ball to root-ball. That is a mistake, because the plants respond to the shade that makes by immediately growing up, not out, and the bottom doesn’t get a chance to thicken and develop at all. Allow at least 3 feet between the plants, so that there is room and light to build a solid base for your hedge. Don’t worry, Thuja Green Giant is so vigorous and fast-growing, it is going to fill in sooner than you thought possible.
Start Trimming Early
This is a big part of the secret to a solid, dense hedge right to the ground. Don’t wait until your hedge reaches the height you want, start trimming lightly as soon as it begins to grow, shortly after you have planted it. Just take a couple of inches off at a time, so that you get lots of small branches developing close in to the main stems. As these grow they will give you a dense structure that will stay that way for many, many years. Don’t forget to trim the top a little too, you want thick all the way up.
Allow Enough Width for Development
Nobody want their hedge to take up the whole garden, so we always want to keep it thin, not allow it to spread too wide. But we must be reasonable, and allow enough thickness for the branches to develop a dense structure. Especially at the bottom, it must be wide enough to support the smaller branches that give us a thick hedge. When planting, reckon on a mature width of at least 3 feet, and remember that gradually, over time, it will add ½ an inch a year, so eventually that will become 4 feet, no matter how tightly and carefully you trim.
Trim Your Hedge with a Sloping Face
Although we are talking about this one last, it is the most important one, and it’s an easy one too. When your Thuja Green Giant bushes grow, they want to grow tall, and a lot of their energy will go to the top of the plant. So growth in the top couple of feet will always be stronger, and the shoots longer, than lower down. This is a big part of why, eventually, the bottom starts to thin out, as more and more water and food goes to the greedy upper parts. When we come to trim, we need to take more growth from the top than from lower down, to push that growth back down into the lower branches. If you trim off the same amount all over the hedge the upper part will start to bulge out, taking the lion’s share of the energy, and also shading the lower growth, which just makes the problem worse. The answer is simple. When you are trimming, cut more from the upper parts than the lower ones, so that the side is flat, but it is leaning inwards by a few degrees.
Some professional hedge-trimmers make a simple structure with a few pieces of wood as a guide. Take three pieces of wood, one 6 feet long, one 3 feet long and one 6 feet 8 ½ inches long. Join them together to make a triangle. You will see it has a right-angle in one corner, but if you attach the 6-foot piece at a point 6 to 7 inches inside the corner of the 3-foot piece, that 6-foot piece will make an angle of about 80 degrees to the vertical, not 90 degrees. If you hold the resulting triangle up to the hedge, with the small piece horizontal on the ground, that is the perfect slope for the front of your hedge. Just lean it against the hedge as you trim, and you will always keep the same slope, no matter how big your hedge is.
If that sounds too complex, don’t worry. Most hedge-trimmers just judge it by eye, looking for a slight inward lean, and with a bit of practice that is the best way for all but the most formal, large hedges. If you can see the hedge from one end, and you have trimmed it correctly, you will see that the side has a uniform inward slope. It is hardly visible at all when you look at the hedge straight on.
That Was Easy
If you follow these simple rules, your hedge will be the envy of your friends and neighbors. When they ask how you did it, just pass on the link to this blog. Thanks!