Nothing else in an Australian garden flowers like a flowering gum. For six to eight weeks over summer the canopy disappears under fistfuls of scarlet, orange or pink blossom, and every lorikeet in the suburb arrives to argue about it. The catch is that the wild species comes from a small patch of southern Western Australia and sulks in humid eastern summers, which is why almost every flowering gum worth planting east of the Nullarbor is a grafted cultivar.
Quick facts
| Detail | What to expect |
|---|---|
| Botanical name | Corymbia ficifolia and grafted Corymbia hybrids |
| Mature size | 3 to 6m for grafted garden cultivars, 8 to 10m for the species |
| Position | Full sun, open and airy, away from overhanging canopy |
| Soil | Sandy or gravelly and sharply drained, slightly acidic |
| Water | Deep watering for two summers, then largely rainfall |
| Climate zones | Mediterranean Perth and Adelaide ideal, temperate Melbourne and Sydney good, subtropical Brisbane workable with sharp drainage |
| Flowering | Summer, roughly December to February, with an occasional autumn flush |
Choosing the right flowering gum
Corymbia was split out of Eucalyptus in 1995 and holds the bloodwoods and ghost gums. The flowers sit in broad flat clusters at the ends of the branches, which is what gives a flowering gum its distinctive layered look when it is in full bloom.
For a suburban block, a grafted cultivar is the only sensible choice. Grafting a selected flowering form onto a tougher rootstock such as Corymbia ptychocarpa or Corymbia maculata solves the two problems that kill seedling ficifolia in the eastern states: susceptibility to root rot in heavy or humid ground, and the lottery of flower colour, since seedlings do not come true. Flowering Gum 'Beeliar Orange' is a good example of the type, reaching a manageable 4 to 6m with dense orange blossom, which suits a front yard where a 30m forest gum would be a liability.
If what you actually want is a large shade or avenue tree rather than a flowering feature, the other Corymbias are the better fit. Lemon Scented Gum reaches 25 to 35m with a smooth powdery trunk and citrus-scented foliage, and Spotted Gum reaches a similar height with the mottled bark that gives it its name. Both are magnificent, and both need real space rather than a suburban front lawn. Browse the full Corymbias range to see the sizes side by side before you commit.
How to plant
Plant in autumn in warm areas and in early spring further south, so the tree has a mild stretch to put roots down before its first hot summer.
Drainage is the whole game. Corymbia ficifolia and its hybrids evolved on free-draining sandy gravel and die quickly in soil that holds water around the roots. On clay, do not dig a deep hole. Build a mound 40 to 50cm high and at least a metre wide out of a coarse, gritty soil mix and plant into the top of it. Our guide to preparing soil for planting covers the simple drainage test worth doing first.
Set the graft union well clear of the soil and of the mulch. Position the tree at least 4 to 5m from a house, path or paving, and never under an existing canopy, because flowering gums need full overhead sun to set buds. Stake only if the site is windy, using two low stakes and soft ties, and remove them after the first year so the trunk builds its own strength.
Ongoing care
Watering
Water deeply once a week through the first two summers, then step back. Established trees are drought hardy and frequent shallow watering does more harm than good, encouraging surface roots and keeping the crown humid. Never let an irrigation line run against the trunk.
Feeding
Use a native-specific, low-phosphorus fertiliser in early spring. Standard garden and lawn fertilisers carry phosphorus levels that Australian plants adapted to ancient, phosphorus-poor soils cannot handle, and the symptom is a sudden decline months later. One feed a year is enough; an overfed flowering gum grows soft wood and flowers less.
Pruning
Prune immediately after flowering, before the tree pours energy into gumnuts. Removing spent flower heads encourages a heavier display the following summer. Otherwise limit yourself to shaping the young tree into a single leader and lifting the lower branches. The one job you must not skip on a grafted tree is removing any shoot that appears below the graft union, because rootstock growth is vigorous and will overwhelm the cultivar within a season or two.
Common problems and fixes
Phytophthora root rot. Sudden wilting, then dieback from the top down, in ground that stays wet. This is the single biggest killer of flowering gums in eastern Australia and prevention through mounding is the only reliable answer.
Psyllids and lerps. Small white or brown scaly caps on the leaves with yellow blotching underneath. Healthy trees tolerate them and the pardalotes and thornbills that eat them do a better job than any spray. Only intervene if a young tree is heavily infested, and then use horticultural oil.
Sooty mould. Black film on the leaves following a psyllid or scale outbreak. Treat the insect, not the mould, and it weathers off.
Borers. Sawdust-like frass and weeping wounds on the trunk. Borers attack trees already stressed by drought or root damage, so the fix is improving the growing conditions rather than treating the holes.
Poor flowering. Usually shade, excess nitrogen, or simple youth. Grafted trees generally flower within two to three years of planting; seedling-grown ficifolia can take five to eight years and may never flower in the colour you hoped for.
Frequently asked questions
Will a flowering gum grow in Brisbane?
Grafted cultivars can succeed in south-east Queensland, but only on a raised, sharply drained, full-sun position with good air movement. Humid summers make root rot and fungal leaf spotting far more likely than in Perth or Adelaide. If your soil is heavy clay and stays wet after storms, a golden penda or a native frangipani will give you summer colour with far less risk.
How big does a grafted flowering gum get?
Most garden cultivars settle between 3 and 6m tall with a similar spread, which is why they suit a front yard or a courtyard feature position. The unselected species reaches 8 to 10m in cultivation. Always check the mature height on the label, because dwarf and standard grafted forms look identical in a pot.
Are flowering gum roots invasive?
They are far less aggressive than the large forest eucalypts, but they are still gum roots. Keep a grafted tree 4 to 5m from foundations, paving and drainage lines, and give a spotted gum or lemon scented gum 10m or more.
What birds does it attract?
Rainbow lorikeets and scaly-breasted lorikeets arrive first, followed by noisy friarbirds, blue-faced honeyeaters and eastern spinebills. It is one of the highest-value nectar trees you can plant in a suburban garden, and it pairs well with the species in our roundup of bird-attracting native plants.
Can I grow one in a pot?
A dwarf grafted form will live in a large pot of at least 60cm for several years, given full sun, a free-draining native potting mix and consistent but not heavy watering. It will flower less than a tree in the ground and will eventually need planting out or root pruning.
Ready to plant?
Browse the Corymbias collection for the flowering forms and the large shade species, or widen the search across our Australian native trees. If a nectar-rich, wildlife-friendly garden is the goal, our guides to native plants with red flowers and to building a low-maintenance native garden will help you fill the layers underneath, and plants that thrive in poor soil covers the companions that will tolerate the same lean, gritty conditions.
