Pinder Plants

The garden designer’s guide to using trees


SGD Registered Member Janine Pattison takes a look at how garden designers can make the most of incorporating trees in their work


Trees are invaluable in garden design. They provide a vertical aspect and guarantee a three-dimensional look to the smallest of spaces. A well-placed tree informs the atmosphere of the whole garden and - when the right species is planted in the right place -adds weight to the garden for generations. Trees play an important role in adding structure to a space; creating screening to improve privacy, creating shade and shelter, providing a habitat for wildlife and adding what the planners would call ‘amenity benefit’. These benefits can come in the form of flowers, berries, decorative bark or leaf colour at different times of the year. Trees can be evergreen or deciduous, different shapes from fastigate to weeping and, of course, anything from small to massive.

In our role as garden designers, it is our responsibility to weigh up all of these factors and then decide on how to use trees in our design proposals to our clients. They are looking to us to make carefully thought-out recommendations about what trees to select, what effect will be created and how big they should be when planted.

The checklist that needs to be considered when designing with trees includes some of the following factors;

How much space are we working with and what is the maximum size of tree that the site can accommodate? This will possibly rule out a range of larger species like oak and beechdo we want a tree in the design at all? Is it to provide height and structure, or is it critical for screening an ugly view? Would a large shrub do a better job?its habit be tall and thin (fastigate), dome shaped or would a weeping cultivar suit best?we need to select an evergreen or would a deciduous tree provide a greater season of interest?the tree be a lone specimen or within a group?site conditions are we working with? A site on chalk will suit different species to one with sandy, acid soil.are the main attributes we are looking for from the selected tree; flowers, berries, decorative bark or leaf colour?

Size Matters
The main consideration when thinking about which tree to select, is to take into account the ultimate size of the tree - and also the size the tree may reach after 25 years in average conditions. Regarding ultimate size, trees are usually classified as: small (5-10m high), medium (10-20m high) and large (20m-plus high). Considering a tree may take decades to reach ultimate height and the lifespan of various species can be anything between 30-300-plus years, it is worth having an idea what your chosen tree might achieve in 25 years. This should be considered in terms of height and diameter spread.

The garden designer needs to decide what shape the chosen tree needs to bring to the design. Evergreen trees tend to have a more definite outline shape while deciduous trees often have a more indeterminate shape, especially during the summer. For these trees, the bareness of winter will show off the tracery of the branches and reveal the outline more clearly. As flowers, berries and leaf colour are ephemeral, it is important to select a tree that offers a graceful shape.

There are shapes that trees naturally grow into. These include; columnar (Taxus baccata ‘Fastigiata Aureomarginata’), conical (Picea abies), domed (Prunus maackii), round-headed (Sorbus aucuparia) and weeping (Betula pendula ‘Youngii’). All of these shapes have their place in the garden designer’s repertoire but it is important to check the selected cultivar will display the habit required.

Growing Conditions
The next factor to consider is the conditions the selected tree will be expected to cope with. Every site is different and it is important to match the tree to the site with care. The beech tree (Fagus sylvatica) that thrives in a garden with chalky soil will struggle in one that has light sandy soil while the Snowy mespilus (Amelanchier lamarkii) will be happiest in acid soil conditions. Very wet, dry or very exposed sites will all require care in selecting suitable trees.

Fit for Purpose
The designer needs to consider what purpose the tree is going to serve in the design. If a single impressive specimen tree set in the lawn is needed, then Prunus sargentii would be a good choice for the medium-sized garden. A larger space could support a Catalpa bignonoides which produces large trusses of white flowers with purple and yellow spots in summer, followed by long, thin seed pods. If evergreen screening is required, consider Eucryphia x nymansensis ‘Nymansay’, a stunning tree that produces fragrant white flowers in late summer. The Wild Service Tree (Sorbus torminalis) is a British native and will provide food and habitat to wildlife from birds to insects.

Characteristics
Of course any designer will be very interested in colour and the distinct characteristics of the various species of tree will be very important. Flowers, berries, leaf colour and interesting bark will all find favour. Flowering trees include the yellow-flowering mimosa (Acacia dealbata), the white-flowered magnolia (Magnolia grandiflora) and the pink of the flowering cherry (Prunus pissardii ‘Nigra’). Many trees produce attractive berries, seed pods, fruits, nuts or cones and these seeding mechanisms can be used to extend the season of interest of a tree. If young children are going to be using the garden it is worth avoiding the varieties that produce poisonous issue. The Sorbus genus are reliable producers of clusters of bright berries in late summer and the ornamental crab apples (Malus spp) produce both flowers and vivid-coloured fruits.

Some of the best trees for attractive bark include; the Snakebark maple (Acer davidii) with vertically striped green and white bark, the River Birch (Betula nigra) with distinct pinkish-orange shaggy bark and the Paperbark Cherry (Prunus serrula) with polished red-brown bark.

Foliage effect
However colourful, flowers and fruits are fleeting, so for year-long interest it is vital to select trees that have striking and beautiful leaves. Gold and yellow foliage brings sunshine into the garden even on dull days and can add a fresh effect to the surrounding planting. Two of the best to achieve this are Robinia pseudoacacia ‘Frisia’ and Gleditsia triacanthos ‘Sunburst’. Silver and grey leaves reflect the light and bring a Mediterranean look to a garden. Many grey leaved trees can cope with drier than usual conditions and they work very well with white flowering plants. The olive (Olea europea) and the Whitebeam (Sorbus aria ‘Lutescens’) are two excellent examples. Red and purple foliage needs to be used with care. It can have a dour effect on a space as it absorbs light but can work very well if used as a foil for lighter coloured plants around it. The purple-leaved plum, Prunus pissardi ‘Nigra’ has leaves and shoots of dark purple while the weeping copper beech ‘Fagus sylvatica ‘Purpurea pendula’ makes a small but perfectly formed tree suited to smaller spaces.

Variegated foliage can be very effective as the two colours are clearly visible close up but give a hazier look from a distance. The variegated maple ‘Acer platanoides ‘Drummondii’ has large mid-green leaves with a creamy-white margin. The evergreen holly ‘Ilex x altaclerensis ‘Golden King’ if situated in full sun will produce grey-green leaves with a broad gold margin.

Autumn colour
Some trees respond to the shortening days of autumn by changing colour and this can add real impact to the garden. As they prepare to drop their leaves for winter they give a last great display of gold, yellow, bronze, red, orange and crimson. When this is combined with gentle autumn sunlight, these trees can give a truly dramatic demonstration of the garden designer’s skill. The Paperbark Maple (Acer griseum) turns gloriously red and scarlet while the Persian Ironwood (Parrotia persica) opts for orange and gold.

Trees for Chalk
Catalpa bignonoides
Juglans nigra
Morus nigra
Paulownia tormentosa
Sophora japonica

Trees for Clay
Acer sp.
Carpinus betulus
Fraxinus excelsior
Malus domestica
Quercus robur

Trees for Acid/Sand
Ailanthus altissima
Alnus cordata
Eucalyptus gunnii
Koelreuteria paniculata
Robinia pseudoacacia ‘Frisia’

Trees for Damp conditions
Amelanchier lamarkii
Cedrus deodara
Parrotia persica
Prunus padus
Pyrus ‘Chanticleer’

Trees for Exposed Sites
Acer campestre
Betula pendula
Gleditsia triacanthus
Sorbus aucuparia
Tilia cordata

Trees for Coastal Sites
Acer pseudoplatanus
Populus alba
Sorbus aria
Sorbus intermedia
Quercus ilex