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“We’ve got used to seeing considerable leaf loss in less winter hardy varieties over the years but most were able to recover and go on to deliver reasonably well,” he notes. “In many cases, by thinning out crops planted too densely in the first place a good touch of winter probably did them a favour.

“We’re facing an altogether different reality this season, though. Hard and persistent frost came upon us suddenly and early, leading to the coldest December for more than 100 years. Unlike last year, the crops hadn’t had the chance to harden off before they got hit. And many were yet to be protected by a blanket of snow. Either that or the snow had receded ahead of the pre-Christmas icy blast.

Northern Crops Written Off
“I’ve been out to several concerned northern growers to find whole fields of completely frost-blackened OSR. With roots as well as shoots turned to stinking mush, the crops are a total write-off. As much of the country also saw serious frost without snow cover I’m seriously worried about the prospects for many other growers; especially as we’ve yet to experience the main part of the winter as well as any damage from frost-heave once the cold finally relents.”

With climatologists predicting a greater frequency of extreme winters ahead, Philip Marr is adamant that UK breeders and growers are going to have to prioritise winter hardiness in their OSR varieties to a far greater extent than they’ve done to date.

The 50 varieties he is examining at Masstock’s Brotherton SMART Farm provide clear encouragement as well as serious warning signs in this respect. Temperatures of below -10⁰C for many days from late November in the absence of snow cover put a particular strain on all plots emerging from early September drilling.

As a result, some varieties had already lost 80% of their plant populations by Christmas. Others, however, came through the severe stress test almost unscathed, demonstrating far better winter hardiness. 

“The low biomass hybrids, with their vigorous rooting but prostrate early semi-dwarf growth habit and very low growing point, have been particularly impressive,” Philip Marr reports. “The most vigorous hybrids appear to have coped better than the less vigorous ones too, as have some pure lines.

“Most noticeable, though, has been the extent to which varieties from some breeders are faring very much better than those from others. This may be due to the germplasm they’re working with or the extent to which their breeding programmes involve testing under the more extreme continental conditions of Eastern Europe alongside the milder maritime west. Either way, the differences are very obvious.

“Winter hardiness, as well as other valuable risk-minimising characters like stem canker and pod shatter resistance seem to have been bred-out of many OSR lines in the pursuit of gross output,” he reasons. “This is something for which our approvals system has to bear a good measure of blame.

“Everyone must appreciate that low risk is every bit as important as high output in commercial practice. What really sets the best OSR varieties apart is their ability to deliver consistently whatever the conditions. If we are to learn anything from this year’s experience it is that yield stability rather than headline yield needs to be the real driver for variety choice.

“After all, as those in the Nordics and Baltics have always understood, no amount of yield potential is worth anything unless you can get your crop to survive the winter.”

In this context, Philip Marr suggests growers keen to protect themselves against the sort of winter risks that have become increasingly evident over the past three seasons need to look increasingly to varieties like Excalibur proven to perform in countries like Sweden, Poland and the Ukraine as much as in the UK.

He also advises them to do everything possible agronomically to safeguard future  crops, boosting their early rooting capabilities and ensuring balanced autumn micro-nutrient nutrition as well as seedbed nitrogen to build the most robust physiology.

Take Winter Hardiness Seriously

“It’s high time the whole OSR industry took winter hardiness seriously,” stresses Philip Marr. “Too many people have ignored the signs and kept their heads firmly buried in the sand over this and other vital risk-management characteristics. This season looks like being a major wake-up call.”