With the first flush of spring growth well underway, it won’t be long before your hedges need trimming. Hedges are the basic architecture of many gardens, and the privacy and shelter they bring are essential for creating a personal garden space. Often they have a practical purpose, sheltering you from neighbors or traffic, but they also give form and structure, creating a stage for your plants to strut their stuff on.
Popular hedging plants like Thuja Green Giant have a natural density that makes it easy to grow them into solid green walls, but you also need to treat them right, and good hedges follow some simple rules for success.
Follow These Six Tips for the Perfect Hedge
- Trim regularly – the more you trim, the denser it gets
- Trim while your hedge is young – waiting till it reaches full-size is a mistake
- Trim in the right seasons – too early, or too late, can cause problems
- Slope the sides – an inward slope keeps the bottom green and healthy
- Narrow the top – round or square, a narrow top sheds snow and ice
- Feed and Water – like a lawn, you need to replace what you removed
Old-time gardeners don’t waste their words. They say, “The more you trim, the denser it gets”, and they are right. When you cut the tip off a growing stem, of any plant, it produces several new shoots a little below where you cut. Buds at the ends of stems produce a plant hormone that stops the dormant side buds lower down from growing. When you cut off that bud they are released from control, and spring into action. Think of how many tips you cut off with your trimmers going over a hedge. Multiply that by three or four, and you can see how many new stems you have. Many stems give us the crowded, dense growth that makes the perfect green wall. It really is that simple.
Trim from an Early Age
If there is one single mistake made when hedges are planted, this is the one. It seems logical that you would leave your hedging plants, like Thuja Green Giant, to grow to the size you want and then start trimming. But logic is not your friend on this one. A solid hedge that is resistant to wind and snow needs a strong internal structure of many short branches. Taking off just a little growth as your hedge is expanding will give you that sturdy structure. If you wait until it has grown taller, then all the density will be on an outside ‘skin’, and that makes your hedge vulnerable.
Start trimming as soon as you see new growth on your new hedge. Just take off an inch or so, regularly, and you will see how quickly it becomes solid. It will still grow up almost as quickly as if you left it alone, but this time you will have many branches, making a tough and sturdy hedge.
Trim in the Right Seasons
There is a rhythm to plant growth, and to the seasons. The longer days and warmer temperatures of spring trigger a big flush of growth, drawing on reserves stored in the previous year. The buds for that growth develop in late fall and early winter of the year before. So you need to let that first flush mature before trimming, as it is the new foliage that keeps your hedge dense and green. If you cut it all off, the older parts now have to make new buds to replace it, and the older leaves soon fall off, keeping the surface of your hedge always thin and weak.
To allow room for that new growth, without letting your hedge get bigger and bigger, you need to trim in fall, leaving all winter for the new buds to form. This also gives you perfect, tight hedges in winter, when they are especially prominent and visually important. When to make that last trim of the season depends on where you live. In colder area you should allow a full month before the normal beginning of cold temperatures and the chance of ice and snow – the odd morning frost is fine. That probably means mid-September is the latest time. In warmer areas you can trim later, often up to the end of November, depending on your climate.
Once the spring flush has started to darken in color, trim it, leaving a couple of inches of that fresh new growth. That trim will stimulate some more growth – a lot in a young hedge, less in an older one. How many times you cut between now and that vital fall trim, is up to you. At least once is usually necessary, and that will keep your hedge both neat and dense. For a super-hedge, make that two, one in early summer, and another in early fall, if you are in a warmer area.
Slope the Sides
This is another secret that is often ignored. The top growth of a plant is always more vigorous, and longer, than the lower growth. If you trim the same amount from all over your hedge, it will become fatter on the top, and narrower lower down. This will shade the lower parts and reduce their growth. In a short time the lower branches will die, and your hedge will be bare for several feet at the bottom – exactly where you want dense green growth.
So always slope the sides inwards just a little. You will be cutting more from the top than the bottom, but don’t worry about that. The less you cut from lower down, the better, as long as it is neat and flat. The best hedges have a flat side, like a sloping board, not a curve, and learn to keep that slope even all along the hedge – it is not difficult with a good quality, sharp hedge trimmer.
Keep the Top Narrow
Sloping the sides will naturally keep the top narrow, and that is something to encourage. A narrow top will shed snow and ice better, and the chance of your hedge collapsing is reduced greatly. With a narrow top you can keep it square and flat, if that suits your garden design, although rounding it for a less formal look is even better for shedding snow.
Feed and Water Regularly
Finally, trimming a hedge is like cutting the lawn. You remove material that is part of the strength of the tree, so hedges need more nutrients than untrimmed plants. Have a regular fertilizer program – organic or not, it’s your choice – and water during dry spells. It doesn’t take a lot of time, but that extra care, and the tips we have given, will make your hedge a stand-out feature of your garden.