Choosing plants for a hedge is an important decision. Hedges, whether formal or informal, are an major design element within a garden and will impact on the look of the garden and what can be grown near them.
Hedging used to be restricted to a few plants - yew, hornbeam, beech, holly and box are the classic English-style hedges, with hawthorn for impenetrable stock barriers. In New Zealand our climate allows us to use escallonia, pittosporum, corokia, akeake and many other plants.
Hedging is a great opportunity to 'think outside the square' as we are so often urged today and to make informal hedge of a range of plants that would have been unheard of before. Many old hedges can be allowed to billow and flow, rather than being confined and clipped. Contrast informal hedges and borders with formal, clipped shapes. Many new plants can be tried as formal and informal hedges.
Choose small plants as they will establish and quickly outgrow taller, more expensive plants. Moreover, large plants tend to grow into gangly, open hedges and not the dense compact hedge of your dreams.
Special purpose hedges
Classic architectural hedges Yew (Taxus Baccata) is a wonderful hedge and clips into amazing architectural and elegant shapes. However it does not like wet feet nor very dry climates and Cupressus macrocarpa is a good alternative. Hornbream (Carpinus betulus) and beech (Fagus sylvatica and cultivars) make classic deciduous hedges and, unless planted in a windy position, they cling to their brown leaves into spring.
For a classic hedge with a local twist, New Zealand's totora (Podocarpus totora) makes a lovely, dense hedge. Slow-growing it will require only an annual clipping.
Formal hedges For a dense, formal hedge you need trees that respond to clipping and maintain a clean line, but not necessarily with all the complex shapes and fine foliage of an architectural hedge.
Plants suitable for formal hedges include Escallonia and Photina (Photina 'Red Robin' and P. glabra 'Rubens') are popular hedges, while matipo (Pittosporum tenufolium), lemonwood (P. eugenioides) and Akeake (Dodonaea viscosa) also make good, dense barriers. Holly (Ilex crenata and others), camellias (C. sasanqua and C. x williamsii) and Clethra alnifolia (summersweet) are alternatives.
Ngaio (Myoporum laetum), Corokia (C. cotoneaster), coprosma, and Broadleaf (Griselinia littoralis) can all be trimmed into a formal hedge.
Smaller leaved hebes, pyracantha and silvery Teucrium fruticans will make a low to mid-height formal hedge.
Hedge Plant Types Bare-root or root ball? What difference does it make? Well, quite a lot in terms of cost, timing and effort.
Bare root plants, usually deciduous but many conifers are sold bare root for hedges. Lifted in autumn and sold with no soil on the roots. Less expensive (no potting up costs and shipping is less expensive) make sure the roots are not damaged or over-pruned. Plant in the dormant season (autumn-winter)
Root ball trees and shrubs are larger and lifted in autumn with the root ball, including soil wrapped in sacking. Plant autumn to spring. More expensive due to handling costs and shipping. Usually larger plants.
Container plants grown in pots. Some can be bare-root plants that have been potted up, watch for this as they should be grown in the pot for several months before being sold. More expensive than bare-rrot but less than the usually larger root-ball plants. Sometimes very small plants (e.g. box) are available in planting cells at reasonable cost. Plant at any time, except when the ground is frozen or in a drought.
Rootrainer small (to 40cm or 15") plants grown in plastic, sandwich-like containers that encourage strong, downward root growth. Generally less expensive than container plants but more expensive that bare-root. Plant at any time, except when the ground is frozen or in a drought