RESPONSE TO BELOW POSTING-:In the book "Paulownia in China: Cultivation and Utilization" by staff of the Chinese Academy of Forestry published by Asian Network for Biological Sciences and International Development Research Centre 1986 (reprinted 1988) it states "...the wood is pale yellow to pale red. The demarcation between sap and heartwood is not clear. Usually there are only one or two annual growth rings in the sapwood. The heartwood is wide and its texture is fine to rather coarse, if fast grown with wide growth rings. Pores in rings gradually diminish in size outwards and the place where the ring starts usually does not form a clear early wood strip. Therefore, it is semi-ring porous to ring porous with very narrow growth rings." Paulownia timber is very light but has a strength to weight ratio. Wood fibres medium in length. Air dried density (15% moisture content) is 0.26-0.33 g/cm3. The 0.27-0.37% shrinkage coefficient is smaller than commonly used coniferous and broad-leaved woods. At 09:06 PM 11/05/97 +0100, you wrote: >Apologies for the delay in replying. > >I have been looking for more information on Paulownia as it is not a >commonly grown species in the UK (if at all) but, I was interested in >the wood science of the question. > >I believe Paulownia is a broadleaved tree, but have not found whether it >is a diffuse porous or ring porous species. As a hardwood, it will not >obey the generalisation which you mentioned, of wider growth rings being >equated with reduction in timber strength. For the hardwoods there are >instead two typical patterns. > >A ring porous species is likely to increase in density as the growth >ring widths increase (the extra growth is mainly in the more dense >latewood), which is why when you select your axe handles etc. you chose >one with wider growth rings (they tend to be of ash or hickory which are >both ring porous species). If on the other hand the species is diffuse >porous there has been little evidence so far of any trend in strength >with growth ring width which cannot instead be explained by the >juvenility of the wood. > >In most species the juvenile wood is of lower structural value (in the >young tree it serves mainly to facilitate translocation of nutrients and >water) due to wider cell lumens and altered ultra structure of the cell >wall. The juvenile period of growth for any height of the tree will >extend for ten or more years from the pith. I believe that this may be >the issue which you wish to investigate before beginning to grow Paulownia. > >In the literature there are a few authors who have investigated the >pulping and other properties of Paulownia (mainly in Taiwan and China, so >possibly not the same species as the USA grown one) and it seems to be >reasonable, and particle board seems to be another attractive prospect. > >(Sorry, no references because I saw the abstracts only and wouldn't want >to mis-quote people) > >Regards > >Morwenna Spear >afu030@bangor.ac.uk > > >On Tue, 6 May 1997, Gordon J. Esplin wrote: > >> Promoters of Paulownia plantations are claiming incredible growth (4 years >> to 60', 16" at breast-height) and value (eg $800/ cubic meter) for Paulownia >> trees. This seems to be too good to be true. Are there any independent, >> scientific studies on this species?? >> >> My thinking is that the high value is for constuction material, where a >> dense(close growth-rings)wood is required. However, if the tree grows 16" in >> 4 years than the growth rings must be about 2" apart and the wood must be of >> little value for construction (but possibly okay for pulp). >> >> Any thoughts on this? >> > > TOAD GULLY GROWERS - The Paulownia Propagation People http://peninsula.starway.net.au/~toadgully hardy planting stock... plantation planning and management assistance
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