As gardens become more compact, the idea of including a tree in them becomes problematic, as there is a limited palette of suitable trees that actually stay small. I feel gardens need at least one tree to give height, proportion and a sense of permanence. And the shade of a tree in part of the garden provides shelter for some of the many beautiful plants that thrive away from the harsh rays of the sun. On solution is to train a tall shrub by removing the lower side branches flush with the main trunk as it grows so that it takes on the appearance of a tree. I find this look more appealing than a ponderous dome or oval of foliage all the way to the ground, and it also creates space beneath the canopy to grow small shrubs, perennials or groundcovers, either directly planted into the ground or in pots. Whilst the training is best done as the shrub grows, it is also possible to 'lift' the canopy of a mature shrub, even if it by then has developed multiple trunks.
The shape of the canopy can be left as a casual mop or else clipped into a more formal shape such as a cloud or an umbrella. A number of shrubs lend themselves to this sort of treatment. My first attempt was with a purple-foliaged Loropetalum chinense (pictured at the start of the blog). The removal of the lower branches immediately gave it more presence in the garden and I underplanted it with various rhizomatous Begonia, bromeliads and Iris japonica, all perennials that can grow in a shallow stratum of soil. The Loropetalum is clipped over into a sort of mushroom shape after flowering every year.
My next subject was a tall species of Rhaphiolepis indica shrub, which I trained from a young plant. I was surprised how high and wide this shrub can get if allowed to grow naturally (unlike most of the modern cultivars of Rhaphiolepis) and I simply didn't have the space for its normal girth. After only a few years, it now really looks quite like a small tree and flowers happily high above the plants sheltering below.
A golden-leaved form of Duranta erecta called 'Sheena's Gold' was the next shrub to get the treatment . It was a fairly old plant by the time it was pruned and had multiple stems, but I think this can actually add a quirky dimension to the final result. This is pruned into an umbrella shape and I have recently underplanted it with some tufts of gold-foliage Acorus gramineus 'Ogon' , which will tolerate shade, and will soon add in some Sedum mexicanum 'Gold Mound'.
The angel trumpet - Brugmansia species - is a good shrub to train to a single trunk as it can be a fairly untidy-looking shrub. It is also possible to grow such a 'tree' in a large pot. It can be pruned very hard in late winter to keep its canopy under control. There are various species and cultivars with single and double flowers in hues of white, yellow, apricot and pink. They have flushes of blooms throughout the year and provide a wonderful spectacle when the branches are smothered in the enormous trumpet flowers.
Camellias are also classic shrubs that can be converted into small trees in this way. Sasanqua camellias are possibly the most suitable, as they have a more open, willowy structure than Camellia japonica. Reticulata and miniature-flowered Camellia are also amenable to the treatment. They are excellent for part-shaded spots in the garden and by removing the lower branches, other plants can be grown to add to the scene when they are in bloom, such as snowflakes, forget-me-nots, primulas and hellebores for the reticulata and minature-flowered camellias and Streptocarpus hybrids , shrubby Begonia, Japanese anemones and any of the numerous easy-to-grow and attractive Plectranthus species and cultivars for the sasanqua camellias.
My most recent shrub tree has been created from Elaeagnus x submacrophylla 'Silverberry', (ht 2-3 m, previously known as Elaeagnus x ebbingei 'Silverberry'). Sometimes called oleaster, it is a most obliging shrub that will grow in heavy or part shade or full sun! It has attractive dusty green leaves (which have a delightful silvery sheen in spring) with a silvery underside, and has a dense, upright form. Inconspicuous perfumed flowers appear in late summer and autumn. It is drought tolerant once established. Now that it looks more like a small tree, I have underplanted it with silvery Plectranthus argentatus, to echo its tints.
Other potential subjects for shrub trees include Viburnum tinus (laurustinus), Syzygium species and cultivars (lilly pillies), Murraya paniculata (orange jessamine), Photinia cultivars, Rondeletia amoena, Tibouchina lepidota, Justicia adhatoda and Euonymus japonica cultivars. I'd love to hear of other pruning experiments gardeners may have made with shrubs.
18 Oct 20
Although my garden is semi-tropical in nature now, I still have some vestiges from my cottage garden days!
11 Oct 20
Consider training a shrub into a small tree.
04 Oct 20
October is iris time in Sydney gardens: the best are the tall bearded irises and Louisiana irises.
One crowded hour
27 Sep 20
Much can be achieved in regular short stints in the garden.
20 Sep 20
We may not be able to grow massed displays of tulips in our climate, but try some of these South African corms instead.