Planting a hedge or screen is an investment – not just in money, but in time and effort. You wouldn’t make a financial investment without planning, and the same goes for planting too. While there are other important things, like soil preparation, correct planting techniques, after-care and good trimming, all of these count for nothing if the basic step of spacing has been neglected. Plant too close and your hedge will become thin at the bottom, with plants dying out as the strongest win in a battle for survival. Plant too far apart and you will first be waiting for ever for it to fill in, and always have an uneven face, with ins and outs, instead of that perfect flat surface that is the sign of a good hedge. So let’s consider how to space your plants correctly, thinking especially of that most popular evergreen of all for hedges and screens – Thuja Green Giant.
Basic Hedge Spacing Rules
For tight hedges – one-quarter of the mature width of your trees
For screening – a little more than half the mature width of your trees
For extra-solid screening – plant a staggered double row
In poor, drought-prone soil – reduce spacing by 25%
Remember to add room for the width too.
Spacing for formal, clipped hedges
Hedges are based on planting close, so that the trees grow together into a continuous mass. But you have to be careful. Sometimes it is recommended to plant root-ball to root-ball, that is, to pack the plants into a trench with the roots touching. Not only does this take a lot of plants, it results in a poor hedge. It does push the plants into growing tall, so you get the height you want quickly. This is probably where the idea came from, and for a few years it can look great, with a nice dense hedge. But after a few more years you will start to see problems. First, some plants will die, as the ones that were a bit more vigorous to start with begin to take over. You will suddenly see plants turning brown, and the foliage falling to the ground. Once they become bare you need to remove them, leaving gaps in your hedge – never what you wanted! Over time the spaces may fill in from the surrounding plants, but until that happens you have a really ugly hedge.
Even if you don’t get gaps, pretty soon the lower parts of the hedge stop growing, and it thins out just where you want it to be thick and green. Eventually the lowest branches begin to die, and your hedge loses that ‘green to the ground’ look that is so desirable.
Much better is to allow enough room for each plant to develop, while keeping them close enough that in a few years they merge into a solid wall. How close is that? If of course varies with the plant you are using. As a rule-of-thumb, check out the mature width of the plant. Taking Thuja Green Giant as an example, the mature width is 12 feet. So take 25-35% of that, and we have 3 or 4 feet. That is the ideal spacing. It’s that simple. The closer spacing will give you a solid hedge sooner, and the wider spacing will save you money by reducing the number of trees you need, but take a little longer to look full.
Spacing for informal rarely-clipped screens
The basic difference between a hedge and a screen is how often you clip it. Screening plants are rarely clipped, or not clipped at all. You might give them a trim or two as they develop, to build denser structure, and then a ‘touch up’ every few years, but that is about it. A hedge is going to be clipped at least once a year, and usually two or even three times, depending on how neat you are, and how much time you have. Especially in warmer areas, plants have a long growing season, so they will need more trimming.
With a screen, we want the plants to grow out naturally until they touch, so in theory we could plant at the same distance as their mature width, but that will take too long, so we usually go closer. Don’t go too close, as the plants will be pushed to grow tall, but stay thinner, which is a recipe for structural weakness as the screen gets taller. So half the mature width is a minimum, which in the case of Thuja Green Giant is around 6 feet. Again, if you are in a hurry you could reduce that to 5 feet, but don’t go any closer. You could stretch it to 8 or even 10 feet to reduce the cost, but if you need a visual barrier that will take a while at such a wide spacing.
A double row makes a denser screen
If you have plenty of room available, and you want a really solid barrier – perhaps for sound protection for example, then a double row is the way to go. This can be done for a hedge or a screen, and the method is to plant in two rows, at a wider spacing, with each plant staggered, so that the plants in one row sit in the spaces between the plants of the other row. Even though the spacing is increased, this method does take more plants, but if a really solid barrier is your goal, then double rows are the way to go. For Thuja Green Giant, space the rows 3 feet apart for a clipped hedge, and 5 feet apart for an informal screen. In each row, a wider spacing of between 5 and 8 feet is good for a hedge, and 8 to 12 feet for a screen.
Planting double rows properly requires careful measuring and lay-out, otherwise you will lose the staggered effect. Careful layout is always needed really – that hedge or screen will be there a long time, and any spacing irregularities will glare at you for years to come!
My soil is very poor, and often dry
It is worth making allowances for poor soil conditions too. Rocky or sandy soil, especially if it is often dry, will reduce the growth of any plant, so you need to compensate for that by planting tighter. Reducing all the above spacings by 20 – 25% will do it, and give you something solid, even under poor conditions.
Don’t forget the width
A common mistake of inexperienced gardeners is to plant a screen or hedge right on the property line, or in a space too narrow for the plants. If your hedge impinges on neighboring property, they can cut it right back to the property line, so plant well inside it. Plant 6 feet inside for a large plant like Thuja Green Giant, or a little less for something narrower. That way all the plant will be on your property, and under your protection.
Similarly, when planning a hedge, especially along a path or driveway, set the back by 3 feet for a hedge and 5 feet for a screen, when using a large plant like Thuja Green Giant. Smaller plants will need a little less, but you don’t want your path to disappear in a few years – working with small plants can be deceptive, so do plenty of measuring!