We originally chose a six year trial for hybrid willow to test the claims made by retailers of the willow for firewood production. Not a particularly scientific approach but, hopefully, it might be useful to share the findings:
These were established willow stools which had been previously cut annually to provide more plants. Bred for biomass production these should normally be mechanically harvested every three years and converted to woodchip but retailers often claim they will also make decent logs at the six year point.
Our observations were that it did exactly what it said on the tin, growing some fantastic rods at the three year point which were an optimum size for both a forage harvester but, more importantly for this trial, a perfect size for feeding into a branch logger. After year three we saw a few stools split in storms but overall little more significant growth. At year six there would be no more than two or three 10″ logs on each rod non of which was of a size that would warrant being split. For us, this is more of an inconvenience than a gain; far better to pop the whole lot through a branch logger at year three. For the record, once dried, the hybrid willow is extremely good kindling product for wood burners and perfect for wood boilers.
Having been asked to grow Alder to supply local smokehouse we had already been taken with how fast it grew. For comparison we planted some one year old transplants to compare with the willow growth. They have produced approximately a quarter of the volume of the willow in this period but it would be interesting to compare the regrowth of an established but coppiced Alder; I suspect the gap would be much less.
With the onslaught of Ash dieback, sycamore was being promoted as an near comparable product to the ‘very best’ firewood. Whilst it was never expected to grow with the same vigour as the other species in our trial it was a useful reference.
An afterthought to the trial our Eucalyptus was introduced a year after the trial had begun. It was bought as seed which in reality put it two seasons behind all the other species. Growth was nothing short of phenomenal providing decent firewood logs at year four/five.
For us there is no debate; for growing firewood logs Eucalyptus is the clear winner. Each of the three Euc varieties trialled (Gunni, Omeo and Mountain Gum) out performed everything else. An added benefit is that even our small plantation provided enough shelter for a Barn Owl to take up residence.
In conclusion and for our own circumstances, Eucalyptus wins for ‘grow your own’ firewood logs for wood burners, hybrid willow wins for branch logging / biomass for wood boilers.