The Oak Collection at Mereweather Arboretum in Australia

The IOS Website Editor has asked me to write an article for about my arboretum, in the Western District of Victoria, Australia. It is at Dunkeld, which is situated at the southern end of the Grampians, a very pretty mountain range, about 250 km west of the capital city, Melbourne. 

Ours is a Mediterranean climate, with hot dry summers and cold wet winters. Rainfall is around 650 mm per annum, mostly in the winter, but if we get a good summer, we may receive up to 25 mm per month. Temperatures range from several days over 40 °C in the summer down to -1 or -2 °C morning frosts in the winter. However, trees have to be able to stand the extremes, if they are to be permanent plants in a collection. Two years ago, we had a summer without any effective rain for six months and a five day run of temperatures over 40 °C. That dry spell killed quite a few soft pines (Pinus subgenus Strobus), but we lost no oaks, as once they are established with their roots down into the clay subsoil, they can easily survive. Some of the tropical species find it hard in our dry weather though. The coldest that we have recorded was -6 °C during the 1982 drought, so that the normal criteria for hardiness in the Northern Hemisphere does not apply to us in Australia. Hardiness in Australia means resistance to heat, drought, waterlogging, wind, animals, lawn-mowers, etc.; only for tropical plants does it mean resistance to cold. Our soil is of volcanic origin, classified as a sandy loam over clay. It is not rich and requires superphosphate applications for agricultural production. The top soil is only about 45 cm deep. Our mild climate and mostly reliable rainfall allows us to grow trees, but we do not by any means have ideal growing conditions.

I am a farmer growing Merino sheep for fine wool production, and after planting shelter belts for stock protection, in 1973 I decided to plant some exotic trees. My reasoning was that on driving around the countryside one would often pass some old orchard trees, pencil cypress, perhaps an oak or poplar, that some old pioneer had planted, and there was no other trace of his endeavors, just those trees to show that he had worked and sweated and persevered. I have the utmost respect for the pioneers of this country and thought that I would leave some trees as a legacy, to show my tenure of this farm. Of course those first few trees triggered an interest that has become a fascinating and rewarding experience: learning about and growing trees from around the world. I inherited a collecting bent, from my father who collected stamps.

Different people go about collecting in different ways; when my interest in a subject is stirred, I like to learn as much as possible and understand it completely. In my day I could not just Google anything, and the many facets of botany in general and trees in particular have held my interest for 40 years. Also I've found that growing a living collection is a big challenge and is always changing; the seeds need to be sourced, germinated, grown, planted, established and when growing they change throughout the season, they start to flower and produce fruit. Whereas stamps look the same every time you look through them.

Our arboretum extends over some 75 hectares with as many species of temperate trees as I have been able to collect and successfully establish. We have in cultivation 200 species of oak and approximately another 70 hybrids and cultivars. Of these, 12 are in section Cyclobalanus and 12 are species of Lithocarpus. We have planted 2 or 3 trees of each species for future pollination and different accessions of the same species have been planted for the morphological variation shown. We have an early planted single Quercus agrifolia that fruits heavily some years, but never does it come true to type. The seedlings are always hybrids. It was interesting that I noticed another grower, writing in an earlier Oak News & Notes, who had the same experience with it. So I can concur about that species. I intend to plant 3 to 5 in a group for future pollination.

Most of my collecting has been through the mail, but I did travel to Yunnan province, China, in 1989, and spent six weeks collecting with five other people, as guests of the Kunming Botanical Institute. We visited areas closed to foreigners at that time. Q. pannosa with its golden-tomentum-backed leaves was a very beautiful tree and common enough in northern Yunnan. But north of Lijiang, we walked 12 km into a magnificent river canyon called Gan He Ba, with towering mountains each side, while it rained solid all day. There we found many Q. pannosa with tan/brown backed leaves, a different color to the commonly seen gold ones. Does anyone know of this difference? The acorns of this species were germinating while still on the tree, making it a real challenge for the collector, but I did manage to successfully cultivate one tree of each type.

Other nice specimens from that trip are Q. franchetii and Q. griffithii. Also Castanopsis delavayi and Q. delavayi, which are planted nearby. It was interesting to note how trees of the same species, but from warmer locations, varied relative to those of cooler origin. We collected Q. variabilis in southern Yunnan, at Simao, and it is inclined to be semi-evergreen, but not more so than Pyrus pashia, from the same location, which is evergreen. Other specimens here in Australia are fully deciduous with spectacular autumn foliage, obviously sourced from much further north. Similar characteristics are seen with Pyrus pashia, which we collected from the same location, and which is evergreen in cultivation. As well as oaks and pears, we have evergreen species of Alnus, Fraxinus (several species) and Ulmus.

In 2008, I attended the IOS Oak Conference at Puebla, Mexico and enjoyed it very much, meeting many very interesting members of the oak fraternity. On the Pre- and Post-Conference Tours, looking at the oaks in their natural environment, at Taxco, in the state of Guerrero, it was common to see Q. urbanii with its rich red velvety new leaves, but on some of the trees the velvet was golden. Between Zacapoaxtla and Cuetzalan we saw the dwarf species, Q. repanda. Much to everyone’s dismay, not one acorn was to be found. But looking intently I spotted a cupule on one bush: 'Where there is a cupule, there must be an acorn!' So searching the ground underneath I was lucky enough to find an old acorn, the shell was starting to deteriorate, but it was still viable. 

While talking to IOS member Kunso Kim, the subject of acorns rotting when sown came up. From my observations, it is mainly Erythrobalanus species that absorb water, and the embryo becomes waterlogged and rots before it starts to germinate. My solution is to remove the pericarp or shell and the acorn will germinate without any problems. If you carefully prize the two cotyledons apart, it starts growing immediately. It can be a big job with any quantity to do. I find it is easier to start at the hilum scar as the pericarp is weakest there. It may seem a lot of bother, but in my opinion it is well worth the effort for rare species.[1]

I carried out this operation on Lithocarpus corneus, from Hong Kong, the acorn of which is about 25 mm in diameter with a flat 'top' and a pericarp that is 5-10 mm thick and bone hard. Needless to say, some acorns came to grief—and the flesh proved to be very sweet. But I did find the meaning of Lithocarpus: literally "stone fruit". See photo; the acorn on the right shows the scales formed into the rings of the Cyclobalanopsis species Q. blakei, also from Hong Kong.

In 2013, I visited Deerlijk in Belgium, to catch up with an old friend Dirk Benoit and look at his amazing nursery, an oak lover’s paradise. Luckily I also caught up with Gert Fortgens and Jean-Claude Weber, there for an Oak Open Day, and was introduced to Eike Jablonski, who asked me about the golden oak that is in Australia. In the past it has gone by the name Q. dentata 'Aurea', but this is not correct. The foliage is identical to Q. aliena and the cupules do not have the long scales of dentata. In my opinion it should be Q. aliena 'Aurea', if that is valid botanically.[2] For those that do not know it, the very large new leaves are rich golden-butter yellow in the spring, changing to green during the season but then regaining their gold-yellow in the autumn. Sorry to be so long responding to your query, Eike.

Mexican oaks grow very well for us and we have around 40 true Mexican species in cultivation, (about 60 counting those that cross the border into the United States). Q. candicans, Q. conspersa, Q. crassifolia, Q. liebmannii, Q. obtusata, Q. oleoides, and Q. rysophylla are all outstanding trees. The endangered Q. hintonii is represented by three trees doing quite well. When raising seedlings it is always interesting to see the variation that often occurs. Several species with very deeply-cut leaf variations we grow are Q. alba, Q. cerris, Q. petraea subsp. pinnatiloba, Q. pyrenaica (collected from the most southerly location for that species) and Q. vulcanica. Why is it that the forms and shapes that we see in nature are so appealing to the eye?

Up until 2000, my collection was keeping up with the rest of the world, but about that time the Australian Quarantine and Inspection Service brought in harsh regulations on the importation of seeds. Nowadays my collecting has largely ceased, but on the positive side, I am lucky to have the collection growing, and that I can enjoy. You have the IOS Website Editor to thank for this article as I am more comfortable down the paddock, planting trees. Also, I wonder whether the thoughts of an Australian farmer can add much weight to the opinions of more learned minds. Any members are cordially invited to visit, if in Australia. We have accommodation available on www.mereweatherestate.com.au

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[1] Editor’s note: As Bill suggests, not everyone is in favor of the technique of removing the shell from acorns to stimulate germination. It is interesting to note, however, that the same procedure was recommended by another Australian collector, Len Stubbs, in an article published in International Oaks No. 4, 1994. It may be the case that by the time acorns reach Australia, having gone from Northern to Southern Hemisphere and switched seasons, a nudge in the right direction might increase germination rate.↩
 

[2] Editor’s note: Quercus aliena 'Aurea' is not listed in the oaknames.org database, but a garden in Australia apparently uses that name. Click here to see a photo of the leaves of that tree in Merry Garth Garden in Mount Wilson, New South Wales.↩