Eucalyptus, Corymbia and Angophora - Cultivation

Introduction

Eucalypts have proven to be reliable and adaptable over a wide range of environments but many are too large for small suburban properties so some care is needed in their selection. In addition, consideration needs to be given to the natural environment and climate of the species being considered. If this is vastly different to that of the local environment, alternative selections may be more satisfactory. The table below summarises features of about 20 popular species as well as indicating some selection criteria for each.


Species Common Name Height (m) Flower Colour Natural Distribution Comments
Angophora
A.bakeri Narrow-leaved apple
10
White NSW Rough, black trunk. Well-displayed flowers
A.costata Sydney red gum
20
White NSW, Qld Beautiful pink/orange trunk when bark is shed. Characteristic "twisted" habit
A. hispida Dwarf apple
5
White NSW Spectacular in flower. Bright reddish-coloured new growth
Corymbia
C.citriodora Lemon-scented gum
30
White Qld Stately and popular tree but too large for normal suburban-sized properties
C.ficifolia Red flowering gum
15
Red, Orange, White WA Unreliable in tropical/sub-tropical areas
C.gummifera Red bloodwood
25
White Vic, NSW, Qld A hardy tree over a wide area but too large for smaller gardens
C.maculata Spotted gum
30
White Vic, NSW, Qld Very beautiful tree with attractive bark. Best in large gardens
C.ptychocarpa Swamp bloodwood
12
White, Pink, Red WA, NT, Qld Excellent colourful tree for warm, humid climates
Eucalyptus
E.caesia Gungurru
7
Pink, Red WA Unreliable in tropical and sub-tropical areas. "Silver Princess" is a good weeping form
E.camaldulensis River red gum
40
White All states The most widespread eucalypt. For large gardens
E.curtisii Plunkett mallee
8
White Qld Good for small gardens in a range of climates
E.erythrocorys Illyarrie
7
Yellow WA Spectacular flowering tree which is best in areas of low summer rainfall
E.forrestiana Fuchsia mallee
7
Yellow WA Flowers are relatively small but the species has spectacular, red buds and fruit
E.globulus Tasmanian blue gum
45
White Vic, Tas Attractive grey-green foliage. For large gardens only
E.leucoxylon "Rosea" Yellow gum
10
Red, pink SA Most reliable of red flowering gums for humid districts
E.macrocarpa Mottlecah
4
Red WA Huge flowers/silvery foliage. Unreliable in tropical and sub-tropical areas
E.miniata Darwin woollybutt
20
Orange WA, NT, Qld Best in tropical and sub-tropical areas
E.rubida Candle bark
30
White Qld, NSW,Vic, Tas. SA Cold tolerant tree with a beautiful white trunk. For large gardens
E.sclerophylla Scribbly gum
13
White NSW Beautiful white trunk with "scribbles". Fairly slow growing
E.scoparia Wallangarra white gum
12
White NSW Quick growing. Beautiful white trunk and weeping foliage
E.youngiana Large-fruited mallee
7
Yellow WA Spectacular shrub which is best in areas of low summer rainfall

Key to Distribution:
WA=Western Australia; SA=South Australia; Vic=Victoria; Tas=Tasmania; NSW=New South Wales; Qld=Queensland; NT=Northern Territory

Pests of Eucalypts

There are quite a number of pests which can attack eucalypts and which may require control in a garden situation. Leaf chewing insects are probably the main concern but, unless damage is severe, there is little reason to resort to chemical controls. Regular observation will enable removal by hand for trees which are being established and, if a few chewed leaves can be tolerated, birds will often keep the infestations in check on larger specimens.

Steel-blue sawfly larvae Scale syllids Galls
Some Pests of Eucalypts
From left - Steel-blue sawfly larvae, scale insects, lerp-forming psyllids and eucalypt gall.

Photos: Brian Walters

Sometimes insects such as "Christmas beetles" can appear in plague proportions and cause severe defoliation which is beyond the ability of the bird population to control. If access is possible, the beetles can be shaken off, collected and disposed of.

   Mistletoe on a eucalypt
   A clump of mistletoe on a Eucalyptus sp.
Photo: Brian Walters

Another chewing pest that can appear in large numbers are steel-blue sawfly larvae. They do most of the damage to a tree's foliage during the night and in daylight hours they gather into groups around small branches. If they are accessible at these times they can be removed by cutting off the branches where they cluster together.

Psyllids (including lerp-forming species) and scale can also cause problems. These are sap-sucking insects and can cause a tree to lose vigour. Again, birds will normally keep them under control but often a strong jet of water directed at the pests will also dislodge them. This may need to be carried out several times. If this is not successful, the traditional treatment with white oil is usually effective.

Some insects lay their eggs into leaves or twigs forming "galls" in which the next generation develop. The galls form as a response by the plant to secretions by the particular insect. To prevent hatching of the adults, galls can be removed by hand and burnt. Often, however, only a few galls occur and are unlikely to damage the tree to any serious extent. They are sometimes attractively coloured and of interesting shapes which can be appreciated as part of the local garden environment. Wasps, flies and thrips are among the gall-forming insects.

People sometimes worry about the appearance of mistletoe on a tree but this is usually unwarranted. These parasitic plants are commonly seen on eucalypts as ovoid-shaped clumps of foliage hanging from the tree's branches. Mistletoes and their hosts have evolved together and, unless the host tree is unhealthy, one or two mistletoe clumps should not cause any problems. In fact they can also be enjoyed as part of the overall garden environment and the fruit may attract the beautiful mistletoe bird.

Once a tree gets to a reasonable size, control of pests by hand removal will be impractical. If serious damage is being caused, it may be necessary to seek advice from the local Agricultural Department.

For further information on mistletoes, see the excellent two-part article by Marion Jarratt published in Australian Plants online. Part 1 is here and Part 2 is here.


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