Mountain Gum
(Eucalyptus dalrympleana subsp. heptantha)

Characteristics

Named after the first conservation officer for the Forest Department of NSW, Richard Dalrymple Hay, Eucalyptus dalrympleana sub-species heptantha or ‘Mountain Gum’ is found growing at elevations above 600m in mountainous regions across the New England Tablelands. This species of white gum can grow in a range of soil types and landscape positions but is commonly found on basalt, and sediments substrates across mid to lower slopes. As a member of the endangered Ribbon-gum – Mountain-gum – Snow-gum grassy forest/woodland ecological community, E. dalrympleana often grows alongside ribbon gum and snow gum as a co-dominant species but can occur as a mono-dominant community or at the ecotone to stands of E. nova-anglica. Under favourable conditions, Mountain gum is capable of growing to a height of 40 m with a large spreading canopy. Like other white gum species E. dalrympleana has smooth white-to-creamy yellow-coloured bark in the upper canopy and along the trunk, however, during the summer months can take on shades of pink and red. As this species often occupies high elevations, E. dalrympleana is capable of withstanding heavy frosts and cold wet conditions common to the Northern Tablelands climate. Like other eucalyptus species, mountain gums develop a lignotuber within their first year of growth seen as a woody tuber at the base of the sapling. The formation of a lignotuber allows the tree to cache resources for future use in regenerating following fire, drought, loss of limbs, grazing and insect attack.

In seasons with favourable environmental conditions, E. dalrympleana can produce rich floral nectar and pollen resources for bees and pollinating insects, with large flowering events attracting a diversity of birds and insects to the tablelands. Similar to ribbon gum, E. dalrympleana is a primary food source for the koala which has in turn reduced in populations with the removal of habitat trees across the landscape. Mountain gums are long-lived, relatively fast-growing trees and are easily propagated making them an ideal species for shade, windbreaks, and ornamental plantings. Like ribbon gum, E. dalrympleana readily forms hollows from dead or fallen branches providing important nesting habitat for woodland-dependent birds and mammals.

Identifying Eucalyptus dalrympleana can prove challenging as it presents similar morphological characteristics to E. viminalis and commonly occurs alongside it. Adult trees of E. dalrympleana often present a spreading habit with an open branching canopy, however, this can vary when tree densities are high. Although the upper canopy bark type is very similar in appearance to E. viminalis, mountain gums often present a shorter stocking height at the base of the trunk with thicker strips of shedding bark. Horizontal scarring from insect attack mid-way up the main trunk can also be indicative of E. dalrympleana, however, this can also present on other white gum species and is not a reliable source of identification. Adult leaves can be similar in appearance to ribbon gum and present as strongly lanceolate and glossy green in appearance (Figure 2). The most reliable means of identifying E. dalrympleana is in its conspicuous juvenile leaves that present as sessile, opposite, grey to blue-green in colour and rounded to roughly ‘heart-shaped’ (PlantNET, 2022). Juvenile leaves are commonly found on young seedlings but are also visible as epicormic growth throughout the crown of trees that have undergone recent disturbance from drought, fire, grazing, or insect attack. 

Mountain gum flowers between February and September, with fruit being held in the canopy over a further 12-month period, dropping seed intermittently throughout that time. Flowers are arranged in umbels of 3 to 7 buds and develop into cup-shaped fruits throughout winter and into spring (Figure 2). Mountain gum is not known as a heavy fruiting white gum species, with the majority of fruits being held on the northern side of trees that have access to ample groundwater.

Threats

Mountain gums are a key member of the endangered Ribbon-gum – Mountain-gum – Snow-gum ecological community and are an important habitat tree for native fauna. Since the introduction of agricultural development on the Northern Tablelands, E. dalrympleana alongside other members of the Ribbon-gum – Mountain-gum – Snow-gum grassy woodlands have been successively cleared across the Northern Tablelands with many of the remaining stands of E. dalrympleana now heavily fragmented and disproportionately composed of senescing adult trees. Due to continued agricultural activity amongst remaining communities, populations of E. dalrympleana are still in rapid decline with many struggling to recruit new saplings as grazing and fertiliser pressures limit natural regeneration. As such E. dalrympleana has been listed as an endangered species under the biodiversity conservation act of 1999 (OEH, 2022).

The University of New England is currently working on a number of projects that aim to conserve and better understand the ways in which populations are likely to respond to a changing climate. Due to the majority of the remaining populations occupying private lands, local landholders have a unique opportunity to play a pivotal role in conserving and expanding this unique woodland community. To learn more about how you can contribute, see our techniques and resources sections.

Key features

• Grows above 600 m elevation

• Can tolerate heavy frosts and cold conditions

• Often located in mid to lower slopes on fertile, deep soil substrates including basalt and sediments

• Commonly co-occurs with Snow gum and Ribbon gum, and other species including Yellow-box and Red-gum

• Typically flowers from February to September, with fruit held in the canopy for 12 or more months

• Important source of food and habitat for native animals such as koala, woodland birds, and pollinating insects

References

OEH – Office of Environment & Heritage (2022). Ribbon gum - mountain gum - snow gum grassy forest/woodland of the New England Tableland Bioregion - endangered ecological community listing. Retrieved from https://www.environment.nsw.gov.au/threatenedspeciesapp/profile.aspx?id=20040#Threats  accessed on 17 June 2022.

PlantNET - The NSW Plant Information Network System (2022). Eucalyptus dalrympleana subsp. Heptantha. Royal Botanic Gardens and Domain Trust, Sydney. https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=in&name=Eucalyptus~dalrympleana~subsp.+heptantha accessed on 27/06/2022