White hardwood felling season: Waiting for the wane

Nothing turns a house into a home, quite like the rustic charm of solid wood. When revamping and furnishing our homes, hardwoods are often the material of choice – but how many of us are aware of the journey they to reach us?

For a lot of sawmillers, November is felling season for species like Sycamore, Ash and Beech – the ‘white hardwoods’ family. Harvesting these beautiful white hardwoods is a precision exercise, and some say the art of getting it right lies in the light of the silvery moon…

The first important thing to note, is that all sawmillers prefer to have white hardwoods felled when the ‘sap is down’. This happens in cooler seasons, when deciduous trees lose their leaves, and store sugars in their roots: during this period, the timber contains less sap and is easier to mill.

If white hardwoods are felled when the ‘sap is up’, i.e in the warmer seasons when sugars are being transported to the leaves, the increased sap within the timber will leak and cause it to split, resulting in a loss of yield.

This all makes perfect sense – so where does the moon come in?

Basic science taught us long ago, that the moon affects many of the earth’s processes; and we all know how its gravitational pull dictates the tides. What may come as more of a surprise though, is that the lunar cycle is also thought to influence the circulation of sap around a tree. This is a centuries-old theory, which suggests certain woods (known as ‘moon wood’), display significantly improved qualities when felled during certain phases of the moon. Moon-related guidelines have been passed down through generations within the timber industry, and studies in Switzerland have shown that specific criteria, such as moisture loss, shrinkage and relative weight, are all significantly affected by the lunar cycle.*

As such, some sawmillers will only have white hardwoods felled during a waning moon i.e. the phase during which the moon is furthest from Earth, and therefore has less gravitational pull. During this phase, the sap is closer to the base of the tree, resulting in a drier timber.

Technology Vs. Tradition

In reality though, it’s not always easy getting the timing right: other factors also need to be considered. For example, Sycamore is only felled when all the leaves have been off for about a week. In mild autumn/winters, this allows very little time between ‘sap down’ and ‘sap rise’, so the opportunity needs to be seized when it arises. With Beech, ‘sap down’ happens closer to leaf drop, which is slightly earlier than Sycamore. With Ash, sap starts to fall in September and felling should start when the leaves drop, around late October/early November.

The introduction of kiln drying has meant that some white hardwoods can be felled in the summer. This can be successful as long as the moist timber is moved from forest to sawmill quickly, to avoid splitting.

In addition to splitting, ‘sap rise’ also causes discolouration if timber is felled in the wrong season. This is especially true of Sycamore, which, of all the white hardwoods, is most prone to staining if felled in the summer: obtaining a pure white harvest isn’t easy, and will therefore demand a higher price.

Over recent years we have also seen an increase in discolouration of Ash timber due to instances of Ash Dieback. As this fungal disease continues to affect the UK’s beloved Ash population, it is becoming increasingly difficult to produce harvests of unaffected timber. We sadly have to face the fact, that healthy Ash may not be around for many more felling seasons and we should therefore do what we can to maximise its chances of success while we still have it: specifically, by felling at the right time of year.

Typically, species felled in summer will attract a lower price per m3, so with all this in mind, it’s fair to say that even as technology progresses and enables alternative felling options, to produce a higher quality yield of our favourite woods, felling should take place when nature dictates.

We already know, that every species on our planet has a purpose; a place and function within the earth’s natural infrastructure. Trees play a hugely significant role in that; so the suggestion that our moon is also lending a helping hand is unsurprising – and also quite comforting, don’t you think?

*Source: www.tonewood.ch