Hedges may be formal or informal. A formal hedge is pruned with hedge shears to keep it to the desired form and size, while an informal hedge is allowed to grow more or less naturally with just enough pruning to keep it within bounds.
Prevent Hedges Growing Up Fast
One important thing to remember with hedge plants is to prevent them from growing up too fast. This can be accomplished by cutting them back moderately as soon as they are planted and by nipping the tips of the shoots whenever they attain a length of 8” to 10” inches.
This is heartbreaking to the owner of the hedge, but he will be repaid in later years by having a hedge furnished from top to bottom, whereas, if left unpruned, the growth toward the bottom of the hedge would be sparse and spotty.
Also, when trimming, do so in such a way that the top is narrower than the bottom.
It may sometimes be necessary to cut a hedge almost to the ground if it has grown too large for its position. But do not do this unless there is a reasonable certainty that it is a species that is amenable.
The following are known to break from old wood even when they are cut back severely; boxwood, euonymus, Ilex aquifolium, and I. opaca.
Plants As Great Hedges
Among the deciduous ones, there are acanthopanax, crataegus, and privet. Among the plants which make satisfactory hedges are the following:
Broadleaf Evergreens
Broadleaf Evergreens Berberis Julianae, B. verruculosa. These need very little pruning, merely cutting back any shoots that spoil their symmetry. Set 2 feet apart.
Chamaecyparis Obtusa Var, Compacta
Chamaecyparis obtusa var compacta. Plant 2’ to 3’ feet apart. Not much pruning is necessary. Merely cut off shoots that are out of bounds.
Ilex Crenata
Ilex crenata. Shear to shorten new growth in July. If shoots have been injured by winter, cut off in spring.
Makes a large hedge 8’ feet high or more. If a 2- or 3-foot hedge is desired, use one of the dwarf varieties, I. Helleri, convexa or globosa.
Ilex Opaca
Ilex opaca (American holly), I. aquifolium (English holly), I. cornuta (Chinese holly) and its variety I. c. Burfordi excels as hedges in regions where they are hardy. Set them from 2’ to 4’ feet apart.
They may be expected to reach a height of 10’ or more feet if required, or they may be kept to 3’ to 5’ feet, shearing them twice, once in spring when new growth starts and again in July to shorten new shoots.
Ilex Vomitoria
Ilex vomitoria (yaupon) and I. cassine (dahoon) are suitable for planting in the mild winter climates of Virginia and southward. Space 2’ to 3’ feet apart.
Narrowleaf Evergreens Species
Narrowleaf Evergreens Abies species (fir) and Picea species (spruce). These two may be spaced 2’ to 3’ feet apart according to the size of the plants.
They should be pruned by trimming the young shoots, usually in July, when they have attained their full growth.
Pinus Strobus
Pinus strobus (white pine) is good for use where a tall-growing (up to 10′ feet or more) hedge is required. Pinus mugo (Swiss mountain pine) is excellent for a low-growing hedge. Finally, Pinus sylvestris (Scots pine) is a good choice when the soil is poor and sandy.
All of these pines can be pruned by shortening the “candles” in the spring. Also, cut them back to the first whorl or, when the objective is to reduce the size, to the second whorl.
Taxus
Taxus (yew). This is probably the most satisfactory of all evergreen hedges. It seems to be indifferent to soil conditions, is easily transplanted, will grow in the shade, and breaks well from old wood.
All yews should be pruned by shearing in July and again in spring before new growth starts.
Taxus Cuspidata
Taxus cuspidata (Japanese yew) is the yew most commonly used for hedge-making.
Taxus media, a hybrid between T. cuspidata and T. baccata, includes two varieties, T. Hatfleldi and Hicksi, which because of their columnar growth habits are particularly valuable where a tall, narrow hedge is required.
Tsuga Occidentalis
Tsuga occidentalis (American arborvitae) is excellent as an evergreen hedge for planting in an exposed location. It may be sheared in spring when growth is about to begin and again in mid-summer.
Tsuga Canadensis
Tsuga canadensis (hemlock). This is probably the most satisfactory of all evergreen hedges when the cost of planting is considered.
Plants may be set 2’ to 3’ feet apart in the spring and given an overall shearing at once. Subsequent pruning is carried out during June or July to shorten the new growth.
Deciduous
Berberis Thunbergii
Berberis Thunbergii (Japanese barberry) and its varieties B. T. minor, B. T. compacta, and B. T. pluriflora (column berry) were long used for informal hedges, especially when a thorny, impervious barrier is required. Today Japanese barberry is considered invasive. It forms dense, prickly thickets that crowd out native plants, and it is thought to harbor the black-legged ticks that spread Lyme disease. Pennsylvania added it to its noxious weed list in 2021, so it can no longer be sold or grown there. Check your state’s invasive plant list before planting it, and consider a native shrub instead.
Very little pruning is necessary except the var. minor needs to be sheared at least once a year when it is used as an edging.
The straight species B. Thunbergi can grow to 8′ feet tall and as much or more in diameter, so if you have limited space, you should concentrate on var. compacta or var. Pluriflora.
Berberis Mentorensis
Berberis mentorensis (Mentor barberry), a hybrid between B. Thunbergi and B. Julianae, is magnificent in the fall when its foliage changes to a very strong red (Nickerson Colorfan).
It is a good choice where an informal hedge 6’ feet high is required.
Although it is said to be evergreen in mild climates here, in the mid-Hudson Valley, it is deciduous. Prune wayward shoots.
Euonymus Alatus and E. A. Compacts
Euonymus alatus and E. a. compacts. Neither of these requires any pruning except when it becomes necessary to keep their height down. Caution: Euonymus alatus, or burning bush, is now an invasive shrub. Birds spread its fruit into woodlands, where it forms dense thickets. It is illegal to buy or plant in Pennsylvania, and it is a Restricted Noxious Weed in Minnesota, where only the seedless cultivars ‘NCEA1’ (Fire Ball Seedless) and ‘ZeroSeed’ may be sold. For fall color, native viburnums, gray or red stem dogwood, and red chokeberry are good alternatives.
To do this, it is advisable to cut them back in July; if necessary, they can be cut back into the old wood the following spring.
They are subject to attack by a black aphid which causes the topmost leaves to curl. Because of the difficulty of reaching them by contact spray, the most satisfactory way of fighting these pests is to cut off the affected tips as soon as they are visible.
The variety compactus is better fitted for a small hedge than alatus.
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