Our current work
Oak is one of the more challenging species that Future Trees Trust work with. The seed are recalcitrant, meaning they cannot be dried for storage, and therefore sourcing acorns from the UK is problematic outside of mast years (typically every 4 – 7 years). We are addressing this in several ways.
1/ We are creating a series of clonal seed orchards for oak, one for Q. robur, and three for Q. petraea. This is done by collecting graftwood (referred to as scion material) from the top of the tree and grafting it on to rootstocks of the same species. For species that graft readily (ash, sycamore) we typically obtain scion material by shooting branches from the top of the tree as this is the quickest and most economical way. However, oak is notoriously difficult to graft and shooting graftwood typically achieves very poor grafting success, so each year we are climbing between 25 – 30 of our selected plus trees for grafting. This ensures the best possible quality of scion material. You can read about this in our reports here. We have been doing this for several years now and are making good, if slow, progress. These orchards are expected to start producing qualified seed around 2030-2035. All grafted trees are also being planted in two archives sites, one in Kent and one in Co. Wexford, Ireland, as a conservation measure, and as a source of additional scion material.
2/ Another problem is that our oak trees are experiencing a growing number of threats to their health which are having a huge impact on their ability to survive. The reasons are not clear. Future Trees Trust is a partner in Action Oak, a multi-partnership project to address some of the questions about this most iconic of species. We are funding a doctoral study on the drivers of masting in oak in the UK with support from our major funder, The Patsy Wood Trust.
3/ We have investigated methods of bulking up improved material for quicker deployment to industry. The report – Vegetative Propagation of Oak – What are the best Options? details various vegetative propagation methods and concludes that using cuttings from stock hedges is the most cost-efficient method.
Another problem with growing quality oak that the forester will be familiar with is shake. It is thought that there is a genetic predisposition to shake but an environmental trigger is necessary. Trees with large vessel sizes have been linked to shake, so all trees in our breeding programme are assessed for vessel size, and those with the largest vessels are excluded. Unfortunately, there is a conflicting research problem here, because trees with large vessels (and thus more prone to shake) are some of the biggest and best trees in our programme. They are also the last to flush in spring which is a desirable trait as an avoidance mechanism to late spring frosts. Because of this link with shake, we need to find additional plus trees, particularly Q. petraea to increase the genetic diversity in our clonal seed orchards. If you have fine specimens of oak we would love to hear from you.
Great Oak Hall at Westonbirt, Gloucestershire