Botanic Gardens Trust, Sydney, Australia

Plant some small trees - and give them a hug

Small trees less than 10 metres tall are terrific in small gardens where space is at a premium. One of the biggest issues when choosing a small is deciding on which one, because there is a great range of trees suitable for Sydney’s climate. Options to consider include flower colour, size and shape of the tree, whether the flowers attract birds and insects, deciduous or evergreen, and the tree’s weed potential.

Deciduous trees are a great choice where winter sunlight is desirable. Consider a Cercis canadensis ‘Forest Pansy’ for its spectacular pink flowers in early spring, followed by purple tinged leaves. This tree is ideal for small spaces where a splash of colour is required. If the lolly-pink flowers of the Cercis are a bit too bright, then the range of colours of the crepe myrtle cultivars (Lagerstroemia indica), including white, through to mauve, pink and crimson might prove to be more appealing. Resist the temptation to cut crepe myrtles back hard every year, and allow the branches to reveal their lovely shape, just thin out unproductive inside and crossing branches, and cut off the spent flower heads when you can still reach them. Some of the Magnolia cultivars are also a good choice for winter sun and early spring flowers - if you want to get away from the usual mauve coloured magnolias, try Magnolia ‘Elizabeth’ which has scented lemon yellow flowers in spring, or Magnolia ‘Vulcan’, a slightly larger magnolia with knockout deep red flowers.

If jacaranda flowers announce that summer has arrived in Sydney, then tibouchinas proclaim autumn’s arrival! Consider Tibouchina ‘Alstonville’ for its spectacular autumn flowers, evergreen foliage and a height of around six metres. The Cape chestnut (Calodendron capense) from South Africa, another autumn flowering beauty, briefly loses its leaves in the ‘dry season’, usually early spring in Sydney. Its spectacular pale pink flowers cloak the tree in early autumn, contrasting beautifully with its attractive, shiny dark green foliage. Cape chestnut grows to a maximum height of around 10 metres eventually, but they’re usually somewhat smaller in Sydney gardens.

To attract birds to the garden, consider planting one of the taller grevillea cultivars. ‘Moonlight’, with its elegant pale cream flowers, or ‘Pink Surprise’ adds colour and texture to any small garden, as well as attracting butterflies and nectar seeking birds. The Blueberry Ash (Eleocarpus reticulatus) is another stunning native tree which attracts birds to both the lovely palest pink, fringed flowers, and its bright blue fruits. For something a bit different, Alloxylon flammeum, the tree waratah, with its bright red, waratah-like flowers and attractive, dark green foliage is an absolute winner. The tree grows to about eight metres high. The more widely grown Queensland firewheel tree (Stenocarpus sinuatus) is a suitable substitute if Alloxylon cannot be sourced.

Plant trees in early spring or early autumn; this allows roots to establish well before the hottest part of summer. To give the tree a greater chance of establishing, it’s worthwhile spending some time getting the planting hole right - preferably allow for about 10 cm of backfilled soil under the root ball. Make sure you rough up the sides and base of the hole with a spade or crowbar before planting and backfilling. The trick to backfilling is to resist the temptation to use compost or other organic material, which can become water-repellent, and does not provide good contact between the natural soil and the planting hole. You want to encourage the roots to grow into the surrounding soil as soon as possible, not hang around in the planting hole enjoying luxurious conditions! Just use the soil that came out of the planting hole, discarding any really heavy subsoil (use it for your ‘saucer’ sides), and ‘borrow’ some soil from another part of the garden if you’ve not got quite enough to backfill the planning hole completely.

If the soil is particularly water repellent, apply wetting agent as directed when planting is completed, and incorporate a suitable slow release fertiliser into the top 10 cm’s of the planting hole, usually a small handful for a 300ml pot is more than adequate. For best results, form the soil into a raised ‘saucer edge’ around the tree when it's been backfilled as this helps retain water long enough to soak in to the soil - make the diameter of the ‘saucer’ as wide as possible to maximise water retention, unless your garden is particularly badly drained - in which case don’t use the saucer! It’s also a good idea to mulch the tree, ensuring the mulch doesn’t contact the trunk; also make sure the mulch is no deeper than about 7cm. Apply mulch any deeper and rainfall will often not penetrate through to the soil. Leaves from deciduous trees such as plane trees or liquidambars are perfectly acceptable to use as mulch, and are a good way of recycling them.

Some formative pruning of your new small tree may be required, this is as simple as getting in early and removing any branches that are growing in any direction you don’t want them to (for example, across a pathway, or into a fence) and pruning very low branches from the trunk. From then on, just follow the ‘Three D’s’ of pruning - and remove any dead, diseased or damaged wood as required. Once established, trees benefit from deep watering during dry spells, rather than shallow and frequent watering. Always maintain a layer of mulch to keep the roots cool and prevent excessive evaporation.

Lastly, take some time to stand back occasionally and admire your tree, and perhaps when no one’s looking, give it a hug too!