Eucalyptus gunnii – The Cider Gum
A cautionary note! We frequently get asked about awkward mature “Eucalyptus that have grown too tall in my garden”
So what’s the problem with Eucalyptus gunnii?
The fact of the matter is that there is no problem with E. gunnii the tree species per se. The problem with this precise tree species is entirely as a result of man’s meddling or should we say ‘lack of understanding?’ But as a result of this mis-understanding, E gunnii appears to have given its entire family a bad name!
Popular in DIY stores and garden centres because of its pretty round blue juvenile foliage, E gunnii is mass produced in small smooth-walled plant pots and sold cheaply as a ‘bedding plant’ with no word of caution on the label. This practice of our nursery industry is akin to a pet shop selling live baby crocodiles under the guise of ‘toy dinosaurs’. I’ll leave you to imagine the end-game!
This cute bushy shrub is purchased by the unsuspecting members of the public, who are encouraged to plant it in patio tubs and even hanging baskets! Once it has speedily outgrown this second smooth-walled container, it is often planted out in the garden. Released from the purgatory of root-binding (like foot-binding but for trees) and now supplied with endless food and water, E. gunnii quite simply goes nuts.
‘All tall Eucalyptus species are fast growing, so what’s the problem?’ you ask. Not so fast!
Not all Eucalyptus are biologically equal.
The specific genetic make-up of Eucalyptus gunnii is such that, under the influence of plant-growth-hormone Auxin, this species grows on a spiral. Some other tree species also do this, such as Horse chestnut. The trunk twists as it elongates, like a corkscrew. Over time, wood fibre is laid down in the trunk, but the weight can be unevenly distributed. The tree grows in an unbalanced fashion. Without a stable, fully-functioning root-system to counterbalance the weight up top, E gunnii becomes the horticultural equivalent of the leaning tower of Pisa.
Fast-growing trees cultivated in a tiny smooth-walled plant pots develop spiral root-systems; hardwood corkscrews in fact. Hampered by a permanently damaged root-system, this behemoth of a tree frequently becomes unstable, often developing a nasty lean and when weighing in at 2 tonnes or more E. gunnii can ultimately fall over – usually on a wet windy night in December.
From germination onwards, Eucalyptus that are cultivated in Air-pot containers are not handicapped with a mal-formed root-system. The air-pot-grown root-ball is engineered by the design of the pot and looks like a baby’s bottle brush or spokes of a wheel. Roots radiate evenly from the central root crown resulting in a stable, well-balanced tree.
Air-root-pruned and Air-pot grown Eucalyptus are the only Eucalypts to have a fully-functioning, safe and stable root-system
What must not happen, at any stage, is to pot on any Eucalyptus species, but particularly E gunnii, into a smooth-walled plant pot. They must all be cultivated either in an air-pot container or the ground only. A smooth-walled plant pot raised Eucalyptus that is subsequently planted in the ground should never, ever be allowed to exceed 8-10 feet (2.4-3m) in height. This is to avoid it ever becoming a liability to man, building or car.
Eucalyptus gunnii grows very tall, very quickly, if unpruned and not managed (25m / 75ft or more). In a small garden, E gunnii should be managed from the time of planting and kept small for life through twice-yearly pruning.
One final but equally important point about the ‘bedding plant’ E. gunnii. The smooth-walled pot is not its only problem. The seed from which they are raised is most likely of unknown provenance. This brings into question the reliability of the tree both for form and habit, and hardiness. Provenance, like with antiques, tells the purchaser the origin of the plant. From where was the E gunnii seed obtained? Seed from the cooler south-eastern quarter of Australia, Tasmania and New Zealand will produce much hardier trees for the UK than seed sourced from the warmer parts of Australia. Was the mother-plant of good form and habit? Specialist tree producers always keep records of their seed source and know that they are growing the best available stock.
Many people are unaware that Eucalyptus gunnii is a member of a tribe or family of gum trees in the section of White Gums. E. gunnii subsp. gunnii is the species ‘type’. The most prevalent species in the group, if you will, and the one which carries the defining characteristics for identifying the species. It has ‘cousins’. Each cousin has its own personality traits, but essentially looks like E gunnii in foliage and bark. However, some of these cousins do not grow on the extreme spiral of E gunnii and not all of them have lignotubers from which they can bounce back if cut down by frost, beast or man.
Suggestions for good E. gunnii alternatives – other members of the gunnii tribe;
- archeri – the identical but better behaved dwarf cousin of E. gunnii and our absolute favourite in the family (even though I know we shouldn’t have favourites!). Silvery blue rounded juvenile foliage with a hint of rose-pink. Excellent hedge screen and pruned shrub, can easily be trained as shrub on-a-stick screening tree. Great as cut foliage. Very bushy habit. Lignotuber present.
- ‘Azura’– very shiny, silvery-blue leaves on a smaller Eucalyptus tree. Fabulous as a pruned shrub and in a patio pot. It can easily be trained as shrub on-a-stick or small tree. No lignotuber present, but will regenerate if necessary from dormant epicormic buds on the lower trunk. Much prettier than standard gunnii. However, the hybrid cross E. ‘Azura’ lacks the strong eucalyptus fragrance; we think aroma was lost during the breeding process.
- ‘Silverana’ – intense silvery foliage. No lignotuber present, but will regenerate if necessary from dormant epicormic buds on the lower trunk. Slightly faster growing than ‘Azura’, but still a smaller tree than E gunnii. Only a mild eucalyptus fragrance.
- ‘France Bleu’ – silvery blue strap-like leaves. Very Small. Recommended you keep as a pruned shrub. Incredibly bushy – makes a great screening tree and is good for cut foliage. No lignotuber present, but will regenerate if necessary from dormant epicormic buds on the lower trunk. Good, strong Eucalyptol fragrance.
- glaucescens – the Tingiringi Gum. Large and fast growing. Straight grained and with a lignotuber. Available in 3 flavours provenance sources of ‘Guthega’, ‘Tinderry’ and ‘Central Victoria’. Visit our E glaucescens page to learn more about this very handsome tree
- gunnii divaricata – Blue Ice Cider Gum. Very like straight E. gunnii, but without the heft. A light-weight frame-work, the Blue Ice Cider Gum appears not to lay down as much fibre in the trunk as the species type. In our experience, it is not as chunky as E gunnii over the same growing-timeframe. Main differences are more silvery-blue juvenile and adult foliage and silvery shoots.
- urnigera – The Urn Gum. One of our favourites. Slim-line profile in its formative years, only branch out into an umbrella later in life. Apically dominant, it is reluctant to produce a bushy multi-stemmed shrub, but has a lignotuber. Amazing bark and beautiful blue foliage are strong features of this wonderful species
