One of the principal defining features of many of the great gardens of the world is their hedges. European gardens long ago elevated the hedge to an art form with centuries old plantings forming the backbone of gardens such as Versailles in France and Hidcote in England. All sorts of interesting trees and shrubs are used for hedging and topiary, but several species dominate, namely English box (Buxus sempervirens), Yew (Taxus baccata) and Hornbeam (Carpinus betulus). Many other species are used of course, but there are millions upon millions of plants of the three species I have mentioned, and these are used all over Europe as hedges.
The reason for such lack of diversity is the adaptability and sustainability of the species mentioned, as they will grow for centuries and thrive on the constant cutting that is demanded of them. Understandably early Australian gardeners relied on these tried and trusted options, particularly in southern Australia where the climate is conducive. However, the further north you go the less amenable they become. Some of the other more adaptable plants introduced for hedging, such as privet, have now become environmental weeds of significant in very damaging proportions. Wouldn’t it be good if there were Australian plants that are better adapted to our conditions to fill the bill?
Many of the shrubs found in the understorey of eucalypt forests around Australia are adapted to regular scorching from bushfires. Thus, many have the capacity to rise again when razed to the stump, whether it is by fire or the human hand via the pruning shears. Thus it is eminently possible to design a hedge from an Australian native plant no matter where you are, from the tropical north to the cool temperate climes of Tasmania.
The bottlebrush (Callistemon species and cultivars) is without doubt my favourite option as a hedge plant for a variety of reasons. Not only do they cope with serious pruning, but also they are adaptable to the extreme range of climates and soils that Australian gardeners face. There are also are so many different species and cultivars to choose from, ranging from the very compact Callistemon ‘Little John’ and ‘Matthew Flinders’, to the head high ‘Great Balls of Fire’ or ‘Captain Cook’, then on up to several metres and beyond with sturdy cultivars such as ‘Perth Pink’, ‘Kings Park Special’ and ‘Endeavour’. They are rarely seen clipped into formal hedges but this is something that can easily be made to happen.
Lilly Pillies (Syzigium and Acmena species) have also become extremely popular with the hedging fraternity due to their glossy foliage, fluffy white or pink flowers and colourful, bird attracting fruits. As they have become more common, however, their pest problems have increased and the one which worries many lilly pillies is the pimple psyllid (Trioza eugeniae) which causes masses of unsightly ‘pimples’ on the new growth of plants. It can be kept at bay through two easy strategies, the first is to simply prune off affected growth when you prune your hedge; the second is to plant cultivars and species that are less susceptible such as Acmena smithii and Syzigium australe.
Cultivars of lilly pilly that I would recommend for all round performance and tolerance of pests are the various forms of Acmena smithii with the stand out in my mind being ‘Allyn Magic’ and to a lesser degree Syzygium australe and its cultivars such as ‘Tiny Trev’.
The various species of Westringia are also fantastic hedge plants with coastal rosemary (Westringia fruticosa) already well established with the gardening public as a reliable hedge and screen plant. There are other species worth considering such as Westringia longifolia and Westringia glabra as they all have the attributes to make great hedge plants.
Another group that is underutilised is grevillea, with the ones to consider being the many small-leafed species and cultivars of grevillea such as Grevillea rosmarinifolia and Grevilllea juniperina.
Even the blue leafed eucalypts such as Eucaluptus cinerea can be used to make a very novel hedge if you are prepared to religiously prune it every few months. If it can be done with yew trees in Europe why not eucalypt hedges in Australia?