American Plantsman Discovers Eucalyptus Hybrid

New Hybrid Eucalyptus discovered in the Pacific Northwest

Barclay's Hybrid Eucalyptus crenulata x nitens found in the USA

Gustavo Iglesias Trabado
GIT Forestry Consulting - Consultoría y Servicios de Ingeniería Agroforestal - www.git-forestry.com - EUCALYPTOLOGICS

Fig 1: Juvenile foliage and flower bud clusters of Eucalyptus crenulata (Buxton Silver Gum)

Fig. 2: Adult foliage and flower bud clusters of Eucalyptus nitens (Shining Gum)

We have already discussed in EUCALYPTOLOGICS some examples of Eucalyptus hybrids as E. urograndis (E. urophylla x grandis), E. gundal (E. gunnii x dalrympleana) or E. nitobulus (E. nitens x globulus). Many other examples exist as a result of natural crosses in their native Australian habitats or as an indirect result of human activity after planting compatible trees overseas and letting them cross-breed. For the last 100 years growers have been periodically reporting such cases from the four corners of the world. And today we report what seems to be a new hybrid case: Eucalyptus crenulata x nitens!

Hybrid Eucalyptus Identification: 4 main considerations

1) Close Cousins or not: Taxonomic Distance

• Eucalyptus crenulata Blakely & de Beuzevill. [1939]: Subtribe Eucalyptinae, Genus Eucalyptus, Subgenus Symphyomyrtus, Section Maidenaria, Series Neglectae, Subseries Crenulatosae
• Eucalyptus nitens (H. Deane & Maiden) Maiden [1913]: Subtribe Eucalyptinae, Genus Eucalyptus, Subgenus Symphyomyrtus, Section Maidenaria, Series Globulares, Subseries Nitentosae
  

- Hybrid category: Intra-sectional (Maidenaria), Inter-serial (Neglectae x Globulares)
- Hybridism rank: Common. There are many known examples of natural and man-made Eucalyptus hybrids using species of two different Series within Section Maidenaria.

2) Bee-Made or Man-Made? Checking Habitat Overlap

Eucalyptus crenulata is an endemic species present in just two tiny wild populations in South Central Victoria. Here it survives as part of plant communities where E. ovata, E. viminalis, E. camphora and E. radiata are the only eucalypts sharing its habitat.

E. nitens has a more widespread natural distribution in the highlands of Central Victoria and further North along the Great Dividing Range into New South Wales. Both species share a somewhat close geographic distribution in Central Victoria but their habitats do not overlap and there is clear reproductive isolation between both gene pools. This means natural hybrids between E. crenulata and E. nitens are not possible in the wild. Hybrid strains can only originate from cross-pollination between compatible parent trees of closely related species planted in some other location.

3) Measure the Beast: Comparative Botanical Diagnosis

One of the most useful parameters to aid Eucalyptus species identification is a detailed study of their reproductive organs: flower buds, flowers and seed capsules. Their numbers, shapes and sizes are key to assist taxonomic study and accurate diagnosis.

Fig. 3: Morphologic assessment of purported hybrid Eucalyptus crenulata x nitens. (Click image to enlarge)

For the case of this probable hybrid strain we have the following morphologic clues:

• Lightly crenulate glaucous juvenile leaves (E. crenulata trait, see Fig. 1)
• Verrucose non aristate glaucous juvenile stems (E. crenulata trait, see Fig. 1)
• Distinctively beaked flower buds (E. crenulata trait, see Fig. 1)
• Barrel shaped non globose glossy green flower buds (non E. crenulata trait, should be glaucous)
• Flower buds and seed capsules in groups of 7 or lower numbers (non E. crenulata trait, should be in groups of 11 or more)
• Early transition from sessile orbicular juvenile leaves to opposite stalked falcate leaves before reproductive maturity (non E. crenulata trait, should not show transition to adult foliage)

4) Ask the Parents: Ancestry of the Cultivated Strain

Are you wondering why the "Get to know as much as possible about seed provenance before planting an Eucalyptus" mantra is a good one? Because when a case like this arises, morphology is not enough!

Going further, seed provenance is not enough. Traceability to the original parent trees for at least a couple of generations might be needed. Detective work.

For this case we are lucky enough as to trace back the seed originating this curious specimen to E. crenulata trees planted ex situ from its natural habitat. In this particular location at least another Eucalyptus species grows which could provide all those traits observed as non E. crenulata. And that species is E. nitens (see Fig. 2).

Why Eucalyptus Botany is seldom an easy task

Discussed above, a strange looking eucalypt for which we have followed early and adult growth until reproductive maturity, which allowed observation of apparent intermediate characters between a clear E. crenulata ancestry (verrucose juvenile stems, crenulate juvenile leaf margins, beaked flower buds) and another eucalypt species bearing flower buds and seed capsules in groups of 7, having orbicular juvenile leaves, falcate adult leaves and barrel shaped capsules.

Detective work yielded nice clues of the other parent in this mix being E. nitens, which, as far as we know, would mean a first detailed record of the hybrid strain E. crenulata x nitens, making Barclay's Hybrid an unique specimen and a nice contribution to genecological studies in Genus Eucalyptus.

But...

"At this subpopulation, the mature Buxton Gums are thought to be hybrids between E. crenulata and E. ovata (Adams & Simmons 2000), and the characteristics of individual trees may not be entirely consistent with the species description in the botanical literature (Blakely & de Beuzeville 1939). Hybridisation between related Eucalyptus species is common and widely documented (Pryor & Johnson 1971, 1981; Griffin et al. 1988). Undoubtedly the exchange of genetic material facilitated by hybridisation has been important in the evolution of this large genus (Potts & Wiltshire 1997). (...) Most of the wild ‘Buxton Gums’ at this site are now thought to be introgressed hybrids between E. ovata and E. crenulata (Simmons & Parsons 1976; Adams & Simmons 2000). A limited number of ‘pure’ E. crenulata were recorded from the site in the 1970s (Simmons & Parsons 1976) and early 1980s (Albrecht 1983). However, pure breeding E. crenulata are thought to be no longer present (Adams & Simmons 2000). Genetic analysis of the population is required to confirm this."

White M.; Murphy A. H. & Downe J. (2006)

No matter what, an unique plant!

The previous excerpt points to more detective work needed. Suddendly, Ian's Hybrid has become one of three potential very rare Eucalyptus:

• A first record of E. crenulata x nitens
• A first record of E. ovata x crenulata in North America
• A first record of (E. ovata x crenulata) x nitens

So maybe the thing to do now is a Spaniard annoying some Australian about an Eucalyptus growing in the United States. Aren't these amusing International Plants?

Ian Barclay (BSc Hort. WSU) has been growing rare plants since last century and scattering them all over Washington State (USA) and elsewhere. Among other things he has trialled over 130 species of Eucalyptus trees in the Pacific Northwest as an endeavour to obtain a range of forms and provenances of horticultural merit and to obtain select trees for superior performance and cold-hardiness, which is the most important effort in Eucalyptoculture for Northwestern America since the days of Stan Gessel.

References

• White M.; Murphy A. H. & Downe J. (2006) National Recovery Plan for the Buxton Gum Eucalyptus crenulata. Department of Sustainability and Environment, Victoria.
• Adams, R. & Simmons, D. (2000) Survival, health and recruitment of Eucalyptus crenulata (Buxton Gum) - Base line data and monitoring guidelines. Unpublished report to the Upper Goulburn Field Naturalists and the Department of Natural Resources and Environment, Funded under the Threatened Species Network Community Grant Scheme. NRE, Alexandra.
• Blakely, W.F. & de Beuzeville, W.A.W. (1939) Contributions from the New South Wales National Herbarium 1: p. 37.
• Pryor, L.D. & Johnson, L.A.S. (1971) A classification of the Eucalypts. Australian National University Press, Canberra.
• Pryor, L.D. and Johnson, L.A.S. (1981) Eucalyptus, the universal Australian. In Ecological Biogeography of Australia. (Ed A. Keast). Dr W Junk, The Hague.
• Griffin, A.R.; Burgess, I.P. & Wolf, L. (1988) Patterns of natural and manipulated hybridisation in the genus Eucalyptus L’Herit.–a review. Australian Journal of Botany 36: 44–61.
• Potts. B.M. & Wiltshire, R.J.E. (1997) Eucalypt genetics and genecology. In Eucalypt Ecology. Eds: J.E. Williams and J.C.Z. Woinarsky. Cambridge University Press, Cambridge.
• Simmons, D. & Parsons, R. F. (1976) Analysis of a hybrid swarm involving Eucalyptus crenulata and E. ovata using leaf oils and morphology. Biochemical Systematics and Ecology 4: 97–101.
• Albrecht, D.E. (1983) Land use case study-Eucalyptus crenulata, Yering. Report to Burnley Horticultural College, Victoria (unpubl.).

Other Links

Phenology of E. globulus and E. nitens in Galicia (Northwestern Spain)

Eucalyptus in Brazil: Life of a Clone

GIT's Eucalyptology Topics

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© 2008 Gustavo Iglesias Trabado. Please contact us if you want to use all or part of this text and photography elsewhere. We like to share, but we do not like rudeness.

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Eucalyptus in Oregon: Australia in the Pacific Northwest.

Eucalyptus trials in Oregon Country: Stan & Lee

Some early work with Australian trees in the Pacific Northwest

Gustavo Iglesias Trabado
GIT Forestry Consulting - Consultoría y Servicios de Ingeniería Agroforestal - www.git-forestry.com

EUCALYPTOLOGICS

The cultivation of Eucalyptus in the Pacific Northwest has had to do with trialling of species for relatively a long time now, sometimes as ornamentals and other times as part of forestry hardwood trials. It is however a relatively recent trend, especially if compared to the very old tradition for the cultivation of Eucalyptus in California.

One of the steps in this process of increasing eucalypt growing had to do with the works of an Oregonian forester, keen tree grower and adventurous fan of the Australian trees.

Lee O. Hunt (1912?-2002), who would later be President of the Douglas County Small Woodland Association, started methodic experimentation at nursery and field trials with 14 species of Eucalyptus back in 1971, focusing in those with good prospects for timber production in short rotations and having enough potential tolerance to cold as to be grown in Southwestern Oregon and survive winters there.

Some known Eucalyptus trial locations in Oregon State

Planting at different trial locations ranging from 150 to 800 m altitude took place along the 1970's, and response to frost damage and growth rates where assessed, making it an interesting study of acclimation for the tested seed provenances of Eucalyptus. Some of the known places where these studies and those later ones made by other foresters took place are:

• North Williamette Experiment Station (Oregon State University, Clackamas County), where temperatures have reached absolute minima of -17ºC in the 1971-2000 period. Earlier Eucalyptus trials assessed by Dr. Robert L. Ticknor, who was also President of the American Rhododendron Society.

• Near Bridge (Douglas County, OR, Highway 42, in the western slope of the Coast Range): 4 species planted in 1975 by Lee O. Hunt.
  
• Schofield Creek (near Reedsford, Douglas County, OR, 87 km to the NW of Roseburg): 6 species planted in 1978 by Lee O. Hunt.
  
• Willis Creek Tree Farm (near Winston, Douglas County, OR): 7 species planted in 1979, 8 additional species in 1981, 4 extra species in 1982 by Lee O. Hunt. Suffered temperatures as low as -16ºC during the first winters, albeit in milder winters they did not reach absolute minima below -10ºC.
• Near Warren (to the Northwest of Vancouver, OR) : 3 species in 1984 by Oregon State University.
  
• Near Siletz (Lincoln County, OR): 3 species in 1985 by OSU.
  
• Near Corvallis: 2 species in 1987 by OSU.
  

Some of the eucalypt species trialled for survival %, tolerance to cold and growth rates in Oregon within this period (1971-1987) were:

Eucalyptus camphora - E. cinerea - E. coccifera - E. dalrympleana - E. delegatensis - E. glaucescens - E. globulus - E. gunnii ssp. gunnii - E. gunnii ssp. archeri - E. gunnii ssp. divaricata - E. irbyi (E. viminalis x dalrympleana) - E. nitens - E. nova-anglica - E. pauciflora - E. stelluata - E. subcrenulata - E. viminalis - E. urnigera

The eucalypts of Stan & Lee

Part of the seed used in these horticultural and forestry trials was sourced by Dr. Stanley Gessel (1917-1995), Professor of Forest Soils and later Dean of the College of Forest Resources at the University of Washington (Seattle, WA), who had visited some of the Australian eucalypt forests and brought back to the USA fresh Eucalyptus seedlots from CSIRO. From these seeds he would also be later responsible of plantings within Seattle and a major influence for future eucalypt growers in the shores of the Puget Sound.

Lee O. Hunt's experimental Eucalyptus nursery at Winston provided also several thousand seedlings per year to local private woodland owners interested in fast growing species with an aim to firewood production during the late 1970's and the 1980's, being a vector for the early introduction of many previously unheard of Eucalyptus taxa in Oregon State and the Pacific Northwest.

From those seeds, these fruits

After the trial efforts previously mentioned ceased in the early 1990's, many new species of Eucalyptus trees had well spread as exotic ornamental or landscape trees in many areas of Oregon, Washington and the British Columbia. Specialist nurseries started propagating these and other newer species which were later submitted to cold hardiness tests in the gardens of adventurous exotic plant growers.

As an example of this horticultural trend our friend Ian Barclay, currently involved in The Desert Northwest project, has tested over 115 eucalypt species in Olympia and Poulsbo (WA) from the the 1990's onwards. If you have not yet read about cold hardy eucalyptus in Ian's The Hardy Eucalyptus Page, you are certainly missing a great information resource on these plants.

Eucalyptus in Oregon: where are Lee's trees?

Potential locations of Lee O. Hunt's Willis Creek Tree Farm Eucalyptus trials

(click to enlarge)

Help us find Stan & Lee's trees! If you live near Roseburg or have easy access to Douglas County in Southwestern Oregon, follow the footprints of Lee Hunt, and hunt the surviving Eucalyptus of these old trials. Some 20 to 30 year old at the moment if still standing, they should give hints on adult tree size achieved by these tree species in the area and could be interesting seed sources representative of cold hardy Oregonian Eucalyptus local races.

If you decide to take such a journey, remember to watch these links first:

• Methodology for Eucalypt Species Identification: Collection of Samples

• Eucalyptus Identification: By their Fruits ye Shall Know Them

And do not forget to send us photographs of any of those Eucalyptus trees you might find!

Interesting Literature

Jacobs, Maxwell R. (1970) The genus Eucalyptus in world forestry. Seattle, WA: College of Forest Resources, University of Washington; October 1970.

Ticknor, Robert L. (1974) Landscape tree performance. Circular of Information 622. Corvallis, OR: Agricultural Experiment Station, Oregon State University.

Hunt, Lee O. (1978) Speaking for the Private Woodland Owner. Society of American Foresters Journal of Forestry, Volume 76, 12:1 , pp. 781-781

Hunt, Lee O. (1983) Adaptability of some Eucalyptus species in southwest Oregon. In: Standiford, Richard B & Ledig, F Thomas, technical coordinators. Proceedings of a work-shop on Eucalyptus in California, June 14-16, 1983, Sacramento, California. Gen. Tech. Rep. PSW 69. Berkeley, CA: Pacific Southwest Forest and Range Experiment Station, Forest Service, U.S. Department of Agriculture; 9-13

Hunt, Lee O. & Logan, Robert S. (1986) Propagation of Eucalyptus Nursery Seedlings. Tree Planters' Notes 37(2):3-7

Hibbs, David E. (1986) Stand management: Growing eucalypts in Western Oregon. Extension circular no. 1198 - Oregon State University, Extension Service (USA)

Giordano, Peter A ; Hibbs, David E; Fletcher, R; Landgren, Chal; Oester, Paul & Rogers, Bill (1993) Hardwood Species Trials in Oregon. Tree Planters' Notes 44(1):38-42

Turner, John ; Gessel, Stanley P.; & Lambert, Marcia J. (1999) Sustainable Management of Native and Exotic Plantations in Australia. In: Planted Forests: Contributions to the Quest for Sustainable Societies, Chapter 16. New Forests 7(1-3) & 8(1).

Barclay, Ian (2002) Hardy Eucalypts in the Pacific Northwest. Pacific Northwest Palm & Exotic Plant Society. Hardy Palm International, Issue #50.

GIT's Eucalyptology Topics

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© 2007 Gustavo Iglesias Trabado. Please contact us if you want to use all or part of this text and photography elsewhere. We like to share, but we do not like rudeness.

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