Raspberry is grown in many parts of the world with annual production estimated at 411,000 tonnes. A temperature sensitive fruit, most are produced in the cooler countries of Europe. However, raspberry production is increasing in warmer climates with year-round production in greenhouses. By JOHN WHITE
Dr Mike Nichols has made a convincing case for year-round greenhouse raspberry growing in Practical Hydroponics & Greenhouses (Jan/Feb 2013 Issue #128). Year-round greenhouse raspberry has already been attempted by at least two growers in NZ and this note records some of the experiences of one of these growers in the hope that this information may be of use in any future attempts at year-round greenhouse production.
More than one-third of New Zealand’s population, and hence more than one-third of its market, lies in the upper part of the North Island, but it is generally reckoned that winter temperatures in this area do not provide sufficient winter cooling to allow raspberries to be grown as a commercial outdoor crop, offering possibilities for year-round greenhouse production. A Bay of Plenty greenhouse owner set up a greenhouse raspberry growing project in 2006 and concluded operations after the 2008/9 harvest season.
Varieties fruiting on florocanes were used, and grown in 10-litre black plastic planter bags filled with bark-based potting composts and trickle irrigated with high output emitters. The greenhouse was set up to allow recirculation of the nutrient solution. The planter bags stood in black and white polythene film gulleys laid over 200 x 50mm polystyrene slabs, forming 50mm deep drain channels on each side of the slab to cleanly and hygienically collect the run-off nutrient solution. An outdoor growing area was also established where the planter bags could stand on black and white floor film and be trickle irrigated, but run to waste.
Florocanes were limited to three or four per bag and topped when they were two metres tall before being cooled. Cooling was in a refrigerated shipping container and operated at temperatures down to 0.5°C. Plants could be held in the cold store after the required cold sum had been given, or they could be brought into the greenhouse and started into growth. Once the system was running smoothly, plants were brought into the greenhouse from the cold store every two weeks, thus providing a smooth succession of fruiting through the year.
Practically every bud on the canes produced a lateral shoot, but these shoots grew very vigorously and were so very long that they could form a closed canopy over the paths, shading the lower laterals and limiting their production. The laterals flowered profusely: fruit set was achieved using honey bee hives within the greenhouse. Berries were generally large and of good quality. The closed canopy was also subject to Botrytis infection in some of the crops.
New cane shoots arising from the base during the period between cold and storing and picking were removed regularly. Once fruiting was finished, the bags were transferred to the outdoor nursery, the old canes were cut out and new canes allowed to grow. Regular watering and feeding ensured good, strong cane growth.
Mild conditions in the Bay of Plenty meant that canes tended to continue in full leaf through the autumn and into the winter, but it was essential that the bagged canes be completely leaf free when put into cold storage for chilling. Leaves on canes in cold store developed Botrytis, which spread from the leaf stalks into the canes leaving lesions on the canes that developed rapidly after moving into the greenhouse. It was necessary to apply defoliant sprays to avoid this, and for the canes to have protective fungicide spray immediately before going into cold storage.
Out-of-season greenhouse raspberry production is an established process in cold northern climates—the USA and Canada—but anyone considering year-round greenhouse production in warmer climates of New Zealand or Australia must accept that more research and development work is needed before year-round production can be reliably and profitably achieved.
This experience shows that lateral growth needs to be controlled to avoid excessive length and consequent problems. This growth control probably requires careful steering by irrigation management. These crops were grown in composted bark with high water-holding capacity, and then irrigated at fixed solar integrals, whereas using a growing media with more easily controlled water content (e.g. rockwool or pumice), and an irrigation program that varied media moisture content through the day, would be more effective.
Better nutrition management could also assist with growth control and fruit yield and quality. N/K ratios were varied with the stage of crop development as per some of the overseas recommendations, but it would have been better if the nutrient solution had been recirculated and nutrient uptake monitored by regular analyses of the recirculating solution.
Botrytis was the most severe pest and disease problem for this grower, but any new greenhouse crop must also expect to be troubled by pest and disease not normally encountered in outdoor crops and for which there are no pesticides registered for use on raspberries. Integrated Pest Management will be highly desirable, but will need development for greenhouse raspberries. This experience shows that the yield and quality potential for year-round hydroponic greenhouse raspberries is high, but both technical development work, and brand and market development work, will be needed for it to be a profitable enterprise.
Australian Raspberry Production
Raspberries belong to the Rubus genus, which also include brambles such as blackberry and loganberry. There are also Australian species of raspberry, but apart from the Atherton wild raspberry (Rubus fraxinifolius), these are not grown commercially. Most commercial varieties of raspberry are bred from Rubus idaeus (from Europe) and R. strigosus (from North America).
The major impediment to outdoor raspberry production in NSW is climate, as many areas of the state have summers that are too hot and dry to produce good quality berries. However, some locations can produce high yields of good quality fruit outdoors, provided they have mild summer temperatures averaging less than 30 degrees Celsius. Locations such as the Northern, Central and Southern Highlands tablelands of NSW are suitable. The most recent statistics show Australia produced 2000 tonnes of raspberry fruit in 2002, most grown in Victoria.
The author thanks RGO Greenhouse of Te Puke for permission to publish this information.
PH&G April 2013 /Issue 130