I have always liked formality in landscapes; which is who I am so very rarely asked to design anything. I particularly like how formal features may be used to enhance the appearance of informal specimens. One of the most basic, utilitarian formal features of a landscape is a sheared hedge. Unfortunately, shearing is likely the most commonly abused gardening technique. This is most obvious in landscapes and gardens maintained by unqualified maintenance gardeners; commonly referred to as ‘mow, blow and go’ gardeners or ‘hackers’.

Hedges sheared with vertical sides generally produce more growth near the top and less near the soil level. This occurs because foliage near the top is exposed to more direct sunlight as the lower foliage may be shaded for part of the day. Hedges which extend from east to west will be more evenly foliated on the south side, but may be sparse on the north side with almost all of the new growth on that side occurring at the top.

Very often, shearing does not compensate for the superfluous growth near the top, so that after shearing, the top is still wider than the bottom. This structure only enhances the problem of the lower foliage being shaded. Consequently, the top grows even wider past the bottom and is likely to be sheared the same way later. If this continues, the top extends slightly past the bottom with each additional shearing.

Hedges which face directly south may ‘creep’ toward the south, even if sheared very evenly. If the south side is permitted to extend even a slight amount with each shearing, it will eventually reach beyond practical boundaries. However, the north side will be shaded by the dense superfluous growth on the south side and produce only minimal growth. Conversely to the south side, the north side may lose volume with each shearing. Eventually, the hedge will be closer to the south than where it was initially installed, often with exposed trunks on the north side.

The most effective structure for a formally sheared hedge is with the top slightly narrower than the bottom. Not only does this allow increased sun exposure to lower foliage, but compensates for increased growth higher up. Some hedges maintain this shape between shearing; but others may produce more growth higher up and consequently exhibit vertical sides by the time shearing is again necessary.

Shearing with vertical sides is also practical, but should be maintained more regularly. (I actually prefer privet hedges with vertical sides.) If maintaining vertical sides, the upper part of the hedge will require more aggressive shearing.

Although the height of a hedge may be maintained with each shearing, some garden enthusiasts prefer to allow the height to fluctuate slightly to simplify shearing. Late winter or early spring shearing may be the most severe of the year and extend to where the hedge was sheared at the same time during the previous year. Later shearing may allow a slight increase in height so that the top of the hedge remains well foliated. An eventual severe shearing to the original height during the following winter or spring may be unsightly for a while, but will start the procedure from the beginning.

Because of ‘negative geotropism’, plants prefer to grow against gravity. consequently, even with very even sun exposure, growth is usually more active higher on formally sheared hedges.