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Building A Hedge - Part 2
Designing And Installing Your Hedge
by Jim Kohut, Staff Writer

In the first part of this two-part series (click here to read it again), we looked at the functions that hedges serve in the landscape, reviewed some of the types of hedges, and explored some of the finer hardy plants available for hedging in the North. In this second part, we’ll get right into the design and installation of your new hedge. So get out the spade and the lawn edger, because we’ve got work to do!

Once you’ve determined the basic style of hedge that you require, you’re now ready to get to the technicalities of your specific design. In designing a hedge, it all pretty much comes down to where you plant the individual plants that comprise the hedge. Here the equation gets real simple; the spread between the plants determines the spacing of the plants relative to each other and to the designated planting area (you may also call this the “garden” if you’d like, because technically that’s what it is, although most people don’t think of a hedge as being planted in a garden).

Designing Your Hedge

The key design variable is the density of the hedge. For a natural hedge, the maximum spacing between plants is limitless, although the farther apart they are grown, the less effective the screening will be. The minimum spacing for a natural hedge will determine its density, and should be somewhere in the order of two thirds to as low as half the mature spread. If planted more closely than this, the individual shrubs will grow into each other and lose any distinctive form, ultimately flowing into a single undulating mass.

	Here is the starting point for our project

For a formal or trimmed hedge, the minimum spacing between plants in a row can go as low as one quarter of the mature spread of the plants, but should never go below about 1 foot for most small to medium-sized shrubs, and 2 feet for taller shrubs. But it’s the maximum spacing where most people try to cut costs, and where most hedge disasters occur. Since density should be constant for a formal hedge across its length, and given that different plants have different natural densities, denser plants should be planted no more than two thirds of their mature spread apart, while open plants should be no more than half of their mature width from each other.

Another design consideration for pruned hedges is the desired width of the hedge. If the intended width is greater than half of the mature spread of the individual plants, then the plants will have to be spaced towards the closer end of the ranges given above, while for a narrower hedge, the spacing can be towards the higher side.

To calculate the actual number of plants you’ll need to purchase for your hedge, take the full length of the hedge run as per your design and divide it through by the spacing between the plants as you have calculated above. Subtract one plant from this number to correct for the end spacings, and there you have the number of plants you’ll need to buy.

Plants should also be selected based on the desired height of the formal hedge. A good rule of thumb would be to select plants that have between one and a half to twice a mature height as compared to the desired height of the hedge. If much larger plants are selected, then there is a risk they may unacceptably thin out from the centers as they age, while too small of plants will take too long to actually reach the ultimate hedge height. Of course, this discussion doesn’t apply to a natural hedge, which should be selected based on the actual mature height of the plants.

Stake and mark the design with string

When considering the size of the garden plot for a natural hedge, your key consideration should be maintenance. If you’re installing your hedge in a typical yard setting with a lawn, unless you’re planting a natural hedge with extremely wide spacings in between the individual plants, you are pretty much assured that you’ll have to excavate a full rectangular garden plot, as opposed to simply digging individual holes in between plants. It will become nightmarishly challenging to maintain grass between individual plants that are spaced closely together while at the same time keeping it away from the base of the plants, so don’t even bother setting yourself up for this heartache.

The hedge row should be wide enough to allow for maintenance access without bumping up against the plants. For a formal hedge, it should be about as wide as the hedge is to be pruned. Anything smaller will make maintenance more difficult, while larger is acceptable so long as the hedge is still able to serve its function.

Because you’re essentially creating a garden plot, you’ll need to consider two factors related to the garden itself as opposed to the plants; edging and surfacing. Rather than trying to revisit all the complexities of these two elements, I’ll refer you to detailed Info Sheets we did on each for further reading;

Finally, give some consideration to the time of year that you’re installing the hedge. If you’re using container grown plants for the hedge, you can effectively plant them at any time between the spring thaw and the fall freeze. If you’re using bare-root seedlings or whips, this can only be done in early spring while the plants are still dormant, otherwise you risk serious loss due to transplant shock.

	Cut into the sod using a lawn edger for a fine edge

Preparing The Site

Now that you’ve got your basic design in place, you can begin preparing the site. The first thing you’ll need to do is to stake off the garden plot for the hedge row. Don’t worry about marking off the planting locations for now; you only need to define the edges of the plot itself in the lawn. Get yourself a few handy wooden stakes, a hammer, and some string.

Mark all the boundaries with the stakes, measuring where necessary relative to the fixed points of reference in your design (for example from the edge of a driveway or path). If the plot is conventionally rectangular, you might only need stakes at the corners, while if it is more elaborate, you’ll require additional stakes. If it is very curvy, you could consider using an old garden hose to mark it off. Tie the stakes together with the string so as to delineate the outer boundaries of the plot, with the string a few inches above the grass or soil.

Now, if you’re digging the hedge plot out of an existing lawn, use a lawn edger to cut the sod along the string (or the contour of the garden hose, as the case may be). This will help give you a sharp edge to the border. Once the plot has been completely edged on all sides, you can use a spade or a sod cutter to lift the sod from inside, trying to remove as much of the grass roots as possible. However, it is not necessary to go deeper than this, as you will be digging much deeper individual holes for the plants within this garden and only top-dressing the spaces in between with soil.

Excavate the garden plot and install the lawn edging

If you’re installing the hedge into an existing garden, then you’ll want to clean the space and remove all plants from within the designated hedge row, but you won’t need to remove any excess soil.

At this point, you’ll install your edging against any exposed lawn, if this is how you’re going to keep the grass out of the hedge. If you’re using black plastic lawn edging, you may have to dig out the edges a little deeper to allow enough room to sink the edging. If you’re using a fancier edging such as bricks or landscape ties, this is the right time to prepare the edging as recommended.

Finally, once the edging is in place, fill the balance of the garden plot back to grade level with good quality topsoil. This might only be a dressing if in an existing garden, but you’ll need a few inches of soil here if you dug it out of the lawn. Don’t try and skimp on the soil just to keep costs down; plants send out very important shallow roots near the surface for a great distance, and good soil will help to keep them healthy and happy, particularly if they are planted in rather close proximity for a dense hedge.

	Planting the plants

Planting Your Hedging Plants

You should now have the plants on hand and ready for planting. Using the edges as a reference point, take your wooden stakes and mark off the exact centers of the planting locations for each plant in the hedge. Be sure to mark them all off before you start planting, so that you can double-check to make sure everything is in line and in order, and make changes if necessary.

Now you will plant the hedge plants one at a time. Begin by digging a deep hole that’s at least one and a half times as deep as the pot the plants are coming in, but no less than one foot deep (even slightly deeper for bare-root hedge seedlings). The hole should be at least twice as wide as the pot, but in no case less than a foot wide. If the excavated soil is of high quality, set it aside for later use; otherwise, have lots of good quality garden soil on hand for filling the holes, and distribute the excavated soil in the empty spaces between the plants.

Start by filling the excavated holes half full with water. If they don’t drain in five or ten minutes, you’ve probably got a drainage problem that should be addressed at this stage. Then fill in with some garden soil to a level depth such that the plants are sitting with the tops of their root balls or the crowns (the place where the stems meet the roots) at exactly grade level. This is also the right time to incorporate any slow-release fertilizer such as bonemeal into the subsoil, which will help stimulate root growth.

The new hedge one year later

Backfill to about half the depth of the plants with good garden soil, and then water liberally again. Fill the rest of the hole with soil, and smooth it out at grade level, packing firmly but not compacting it. You can water the soil lightly with a garden hose at this point, but it’s more to hold the soil down than anything else; the primary water supply for the new plant was placed in the bottom of the hole.

Once all the plants are in place, you can either leave the top soil exposed and black, or you can cover the surface with a mulch to conserve moisture and reduce maintenance. In the case of the latter, you may consider first applying a layer of good quality landscape fabric underneath the mulch; this is one of those applications where landscape fabric is highly effective in keeping the maintenance down.

After-Care Of Your New Hedge

As with any new garden, the plants in your hedge will require additional care and attention over the first year. This means frequent watering while the hedge plants are establishing deep roots in their new home, but without creating standing water. You can also expect to have your hands full with weeding the first year, as most imported soils come fully stocked with what seems to be an endless supply of fresh weed seeds. Don’t worry; after the first year, it gets a whole lot easier to maintain.

No matter how difficult you might find this, you’ll want to refrain from pruning your hedge in the first year at all, even if you’re starting a formal hedge. The plants need the first year to settle in to their new homes, and don’t need to deal with the added stress of pruning. Besides, it will be virtually impossible to set any kind of meaningful level for your pruning with a ragtag and disorderly bunch of new plants.

	Gradually break the plants into a pruning regimen

Starting in the second year, you’ll want to ease the plants into a pruning regimen. But again, you’re not going to be pruning as much for form as you will be pruning to train the plants and prepare them for future greatness. Therefore the objective of the initial pruning in the second year is to gradually bring the heights of the individual plants into balance, and to get them thinking about building density rather than height.

For the most part, you won’t need to train natural hedges, except maybe to bring their forms into balance early in life - it’s much easier to shape a smaller plant for the future than to deal with a malformed mature plant. And be sure to always trim out any dead wood each spring, to allow the active growth to fill in all spaces.

As for pruning in future years, that’s a detailed topic that warrants its own Info Sheet; it’s just too involved to cover in this installation article. For now, get your new hedge off to a good start, and get ready to enjoy the fruits of your labors!

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