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Identifying Mystery Eucalyptus: The case of E. gunnii x nitens hybrids... in Denmark!
Gustavo Iglesias Trabado 
GIT Forestry Consulting - Consultoría y Servicios de Ingeniería Agroforestal - www.git-forestry.com - EUCALYPTOLOGICS
GIT Forestry Consulting - Consultoría y Servicios de Ingeniería Agroforestal - www.git-forestry.com - EUCALYPTOLOGICS
We have previously showed you around here different cases of "odd eucalypts" growing in different parts of the world. First, the case of our friend Ian Barclay at the Desert Northwest finding a new eucalypt hybrid (Eucalyptus crenulata x nitens) growing among his ornamental plant stock. Then, some stories about hybrid E. gundal (Eucalyptus gunnii x dalrympleana) developed in France for forestry purposes. And some more blabla about Eucalyptus globulus x nitens, another potentially interesting hybrid choice for timber production.
Today we bring you some more about eucalypt hybrids. In this case, a type with some interest for those growing the ubiquitous Australian trees in the boundaries of their tolerance to cold. From Denmark, after enduring 8 winters, and thanks to Martin Reimers, we take a peek at Eucalyptus gunnii x nitens ... in two botanical plates!
Fig. 1: Botanical assessment of photographic samples leading to the identification of Martin Reimers' mystery Eucalyptus growing in the Northern shores of the Flensburg Fjord, Denmark, as a hybrid Eucalyptus gunnii x nitens. (Click the image to enlarge, 1280 x 1024 pix)
Product of the viable cross of two relatively closely related eucalypt taxa (both E. gunnii and E. nitens belong to subgenus Symphyomyrtus, Section Maidenaria, and differ just as part of Series Orbiculares and Series Globulares respectively, so they are somewhat "close cousins") , this particular interserial hybrid combination would be very unlikely without human intervention, since each species has its habitat at one side of the Bass Strait.
Fig. 2: Complementary botanical assessment of E. gunnii x nitens depicting the juvenile organs of both parent species and the hybrid cross. (Click image to enlarge, 1024 x 768 px).
Interestingly, Martin's tree shows some of the well desired effects of heterosis, and of a lucky combination of inherited good form, fast growth and cold hardiness. Precisely, if at some point we hinted that E. globulus x nitens could be of interest for some addition of cold hardiness to a benchmark species for short rotation timber plantations, this time the addition comes "on the other side of the frost spectrum".
Not in vain, fast growing E. nitens, a relatively cold hardy eucalypt species for temperate atlantic climates, able to tolerate a good number of frost events each winter but not extremely well adapted to harsh winters much beyond USDA Hardiness Zone 8a has, in this case, crossed with one of the cold hardiest eucalypts, the Tasmanian Cider Gum, able to survive in USDA Zone 7a. A promising sign for its, by now, good performance in an area of the world you would not instantly associate to the Australian trees.
Some Interesting Literature...
Listed below, some relevant bibliographic sources for cases like this, which could give the reader some insight on the mechanisms that made hybrid Eucalyptus trees like Martin's possible, and beyond possible, understandable. Reasons enough for compliments to be always sent to the Eucalyptus of France and Tasmania.
Cauvin B, Potts BM & Potts WC (1987). Eucalyptus: Hybridation artificielle - barrieres et hérédité des caracteres. Annales de Recherches Silvicoles 1986, AFOCEL, Paris. pp. 255-303.
Tibbits WN, & Reid JB (1987). Frost resistance in Eucalyptus nitens (Deane & Maiden) Maiden: genetic and seasonal aspects of variation. Australian Forest Research, 17 (1), 29-47 DOI: 0004-914X
Tibbits WN & Reid JB (1987). Frost Resistance in Eucalyptus nitens (Deane & Maiden) Maiden: Physiological Aspects of Hardiness. Australian Journal of Botany, 35 (3), 235-250. DOI: 10.1071/BT9870235
Griffin AR, Burgess IP & Wolf L (1988). Patterns of Natural and Manipulated Hybridisation in the Genus Eucalyptus L'Hérit. A Review. Australian Journal of Botany, 36 (1). DOI: 10.1071/BT9880041
Tibbits WN (1988). Germination and Morphology of Progeny From Controlled Pollinations of Eucalyptus nitens (Deane & Maiden) Maiden. Australian Journal of Botany, 36 (6). DOI: 10.1071/BT9880677
Tibbits WN (1989). Controlled Pollination Studies with Shining Gum (Eucalyptus nitens (Deane & Maiden) Maiden). Forestry, 62 (2), 111-126. DOI: 10.1093/forestry/62.2.111
Tibbits WN, Potts BM & Savva, MH (1991). Inheritance of freezing resistance in interspecific F1 hybrids of Eucalyptus. Theoretical and Applied Genetics, 83 (1). DOI: 10.1007/BF00229235
Bookmark this Interesting Link...
Besides growing several cold hardy Eucalyptus species with good potential for survival in the Eastern coast of Jutland, our fellow forester Martin Reimers has started to put together a wonderful database of performance for recently cultivated Eucalyptus all over Denmark.
Besides a growing amount of information on the history of Eucalyptus cultivation in Denmark, at www.eukalyptus.dk you can find fine photographic examples of E. gunnii (Cider Gum), E. gunnii x nitens, E. perriniana (Spinning Gum), E. dalrympleana (Mountain White Gum), E. pauciflora ssp. debeuzevillei (Jounama Snow Gum), E. pauciflora (White Sallee), E. nitens (Shining Gum), E. urnigera (Urn Fruited Gum) E. rubida (Candlebark), E. barberi (Barber's Gum), E. coccifera (Tasmanian Snow Gum), E. johnstonii (Tasmanian Yellow Gum), E. subcrenulata (Alpine Yellow Gum) and E. delegatensis (Alpine Ash) including detailed records of their cultivation and behaviour in such an apparently impossible location as the fjords, plains and islands of Denmark.
Some of these grow in the grounds of tree famous places as Copenhagen's Botanical Garden , recent receiver of Eucalyptus wedding gifts of Australia to Crown Princes Frederik and Mary; or as Hørsholm Arboretum, the largest collection of trees and shrubs in Denmark. But many do thrive also in the gardens of adventurous horticulturalists and private plant collectors scattered over the country, proving that at least the cold hardiest species within the genus can survive and bloom in yet another piece of Scandinavia.
Also in EUCALYPTOLOGICS... THE EUCALYPTUS OF THE FJORDS
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© 2007-2009 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.
2 Comments by our readers :::
I wonder if the eucalyptus oil of therapeutic value can be isolated in all types of eucalyptus.. Your blog is very interesting and informative. It sure knows how to elaborate on its niche. :)
Hello Snapping Panda person :D
And thanks for your kind words.
No, it cannot :) There are several hundred species of eucalypts, and the majority of them have a typical Myrtaceae organ in their leaves (and sometimes in other tissues), the oil glands (you can call them oil factories :-). But some species do not. No oil glands, no Eucalyptus oil.
Among those having oil glands, some have them in "very small numbers per leaf", which means a tiny amount of oil. Low density of oil glands, little Eucalyptus oil.
And, among those having oil glands in large numbers, much depends on the chemical composition of the oil within the oil glands. It is very variable. Normally just a small number of the range of present chemical compounds of the oil have some therapeutic, perfumary or pharmaceutic value. Lots of crude oil but low richness of key compounds, little value in Eucalyptus oil.
Which means you first need to extract the crude oil, and then you need to refine the oil to obtain the desired essence grade. Not so different from the other oil, but renewable :-)
So, another case of variation from Eucalyptus species to species, variation within a species, and even variation from tree to tree. In this case, for oil yield and oil value :-)
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