Endurance: Highest yielding SRC willow variety available for Spring 2015 planting

It’s been worth the wait but the SRC willow variety Endurance will be available for planting in the spring of 2015. Over the last decade Endurance has Endurance leavesconsistently yielded highly in trials in the UK and Ireland and is the only variety that consistently outperforms Tora, the industry standard (Ref: Willow Varietal Identification Guide).

The variety was bred at Long Ashton Research Station by our very own Kevin Lindegaard in 1998. It is a female variety with many stout stems and broad leaves and comes from a unique cross between the Asian species Salix redheriana and the European Salix dasyclados. Endurance loses its leaves in December which is later than other varieties. This could pose a problem with early harvesting (as the leaves could reduce wood chip fuel quality) but the upside of this is that it has much greater value as a shelterbelt (e.g. as a windbreak). Furthermore, the variety almost certainly has the highest hydraulic roughness of all currently available SRC varieties making it an excellent option for planting for flood mitigation.

In addition, the diverse pedigree means that Endurance is very different from the majority of other willow varieties. This makes it an excellent candidate for mixed clonal plantings to guard against disease and pest outbreaks. It is currently resistant to leaf rust and has low susceptibility to leaf beetles.

High yielding
From all trials planted in the UK and Ireland Endurance has the highest overall mean yield of 11.45 dry tonnes per hectare per year. Endurance has the highest mean yield for performance in the second rotation with 13.3 dry tonnes/ha/yr. On average its yield from the second harvest is 25% higher than the first. From 22 trials it has topped the rankings on eight occasions and been second on three occasions.

Yield results in first and second harvests (oven dry tonnes/ha/yr) and comparison to the industry standard Tora. 

Overall yields from UK and Irish trials



No of trials









% of Tora



Trial results vs Tora (W-L-D)



Endurance trial plot next to a miscanthus sinensis in IBERS, Aberystwyth. This picture was taken on 26th November 2014. Most SRC willow varieties have lost their leaves this late in the season.

Endurance has achieved high yields in all locations tested. Although its best yields have been in Ireland and the West of England and Wales it is also the best performer in the drier soils in the East of England.

Excellent woodfuel quality
Endurance has a high % dry matter content at harvest (50%) meaning that it should be more suitable for samll scale wood chip production than other varieties. Many other willow varieties are up to 57% water when harvested so Endurance has a significant advantage as during drying you will only need to lose 15-20% moisture before the fuel is ready to burn. In addition, it has a higher than average bulk density and one of the highest calorific values (18.3 MJ/kg) of SRC varieties. This means that wood chip will take up less storage space and produce a higher heat output. The only other current SRC variety with similar woodfuel qualities is Endeavour.

Woodfuel qualities of Endurance compared to other varieties

Quality parameter





Mean dry matter % at harvest





Calorific value (MJ/kg)





Bulk density (kg/m3)





All in all Endurance could be the SRC variety the industry has been waiting for. With excellent yields, growth form, woodfuel qualities and versatility you really should be thinking about planting this variety for your energy crop project.

If you would like a quote for planting stock for 2015 planting please contact us.



Information for this article is kindly reproduced from the Willow Varietal Identification Guide written by Kevin Lindegaard of Crops for Energy Ltd and published by Teagasc and AFBI in 2013.