‘We picked raspberries in January’ thanks to LEDs

A TRIAL of LED lighting for horticultural applications has shown dramatic results, allowing a grower to harvest raspberries in January.

Raspberries grew ‘as quickly as in summer’ under LED lighting, says horticultural researcher Willem van Eldik of Dutch research group Delphy.

The crop was planted in November and, under a mixture of red and blue LEDs, grew big leaves ‘as quickly as in summer’, said Willem van Eldik of Dutch research group Delphy, which conducted the trial.

Speaking at the Lux-organised Horticultural Lighting Conference in Utrecht, The Netherlands, van Eldrik said buds appeared quickly and developed nectar rapidly. They were pollinated by bumble and honey bees and the fruit was picked on 31 January 2018.

The trial – which used the summer variety Tulameen (rubus idaeus) – took place in a climate-controlled greenhouse.

A parallel planting of blackberries, which began on 20 November 2017, exhibited flower buds in January with pollination by bees and full cropping on 27 February this year.

It’s hoped that the research will help Dutch growers to have year-round production.

The potential of LEDs is causing excitement in the horticultural sector as, unlike the traditional technology of high-pressure sodium, the lighting can be tuned to the individual variety of crop, a so-called ‘light recipe’.

Each plant needs different light at different times during the day and at different times of its growth. Most growers currently opt for a mixture of blue at a wavelength of 450 nanometres, which helps with chlorophyl and beta-carotene production, and red at 660 nm, which influences germination, plant growth, leave building and flowering.

More red light generally leads to a linear increase in yield with crops such as soft fruits and tomatoes. The lighting can also be tuned to affect the shape, taste and other characteristics of the plant.


  • The next Lighting for Horticulture conference takes place on Tuesday 9 October and Wednesday 10 October 2018 in Portland, Oregon. To see the full programme and register for a place, click HERE.


Picture: Shutterstock 2018