Warmer winters may not provide sufficient chilling for blackcurrants in the UK, delaying the start of the growing season and resulting in reduced yields and lower fruit quality, researchers have found.
Like many fruit crops and woody plants, blackcurrants require a period of chilling before they start to grow in spring. This reduces the risk of frost damage to new buds and ensures that buds burst rapidly in the spring and flower together, when pollinators are abundant.
Speaking at the British Ecological Society’s annual meeting in Birmingham, a research group based at the James Hutton Institute highlighted that milder winters may cause blackcurrant crops to flower later in the year, produce fewer fruit and, over repeated years, have a reduced plant lifespan.
‘Blackcurrants have particularly high chill requirements and so are already seeing the effects of milder winters’, said Dr Katharine Preedy from Biomathematics and Statistics Scotland.
An important UK crop
A key crop worth about £10m a year to the UK economy, blackcurrants are primarily processed as an ingredient and juice for major brands like Ribena – a brand valued at £140m.
Understanding how different blackcurrant varieties may respond to climate change is critical to farmers. About 35% of the crop currently grown is known to require 1,800 hours of chilling below 7°C. But some varieties need far lower temperatures – and others can tolerate warmer temperatures as long as the chilling lasts longer.
Many farmers coordinate processing with apple producers in shared facilities; a delayed blackcurrant season may force them to harvest unripe fruit of poorer quality – or they might miss the chance to process the fruit at all.
‘Blackcurrants are like the canary in the mine. If we can understand what they need in a changing climate, we can apply our knowledge to similar crops like blueberries, cherries, apples and plums’, Preedy added.