Greenhouse Red Raspberry Production in the Pacific Northwest

Chaim Kempler, Research Scientist and Berry Breeder
Agriculture and Agri-Food Canada, Pacific Agri-Food Research Centre
PO Box 1000, 6947 #7 Hwy.
Agassiz, BC V0M 1A0
(604) 796-2221, Ext:224 Fax:796-0359
kemplerc@em.agr.ca

March, 2001

In British Columbia greenhouse production of edible products has been limited primarily to tomatoes, cucumbers, peppers and lettuce. However, producing other high value produce for local and export markets is possible. Consumers want to see fresh raspberries on the market for twelve months of the year, just as they see strawberries, apples or oranges. This desire for fresh raspberries has stimulated production in the southern hemisphere where fruit is airfreighted north from November through to April. Raspberries are also trucked from southern US states and Mexico.

Raspberries are a very perishable fruit and because of the long shipping distances, quality is often poor. Often inferior varieties are grown which results in poor fruit quality in the marketplace that is not up to the standard we are used to seeing in the Pacific Northwest (PNW),. Raspberries are a high value crops that are very suited to winter greenhouse production. Early spring production is possible locally if canes of summer-fruiting varieties are transplanted into greenhouses during their winter dormancy.

Some of the reasons why the PNW is very suited for greenhouse raspberry production:

• Greenhouses are empty during the winter
• Only moderate inputs are needed
• Production is possible under low light
• Production is possible under relatively cool temperatures
• The most successful cultivars for fresh market are readily available
• The PNW area is the leading producer of raspberries in the world

There are several factors and developments that are now in place that make winter production of raspberries possible and successful:

• Consumer demand for a year-round supply of high quality fruit
• High price for imported fruit (winter raspberries are retailed for $6-25 / lb Canadian)
• Commercial availability of bumblebees hives that are needed for pollination
• Effective biological control of pests, making pesticide spray unnecessary and allowing the use of bumblebees.
• Low cost of energy

Fruit-bud formation and rest period requirements of raspberries

Like other Rubus species, raspberries have biennial stems that produce flower buds along the upper ends the first year and than fruit and die the second year. The buds may be on the main cane or on the laterals. Fruit-bud initiation occurs in late summer or fall when cane growth has stopped. In the fall, the onset of rest begins. During this period, rest becomes progressively deeper. Raspberries will not begin to grow even in warm temperatures until their specific amount of chilling required to terminate or break rest are satisfied. The chilling required to break rest varies between varieties and growing conditions is estimated to be between 600 and 1500 hours below 4°C for maximum bud break and growth. Bud growth will occur when plants are exposed to favourable temperatures.

When growing raspberries in the greenhouse the rest (chilling) requirements need to be satisfied before canes are placed in the greenhouse. In the PNW, on average, 600 hours of chilling are accumulated by the first week of December and by January 1200 hours are usually achieved. Long cane raspberry production refers to the method in which raspberry plants are grown for one year to produce canes, its rest requirements are satisfied (naturally or during a period of cold storage) and for fruit productions are moved to warmer location (a greenhouse or warm climate).

Raspberry production in Spain

On the Atlantic coastal area of southern Spain (Huelva) there are 3000 ha. of California- style winter strawberries in production, mainly of the Camerosa variety. Winter raspberries are also produced using the long cane production method. As with strawberries plant, long cane raspberry stock is raised in high elevation nurseries in northern Spain. Raspberry crowns and roots are planted early in the spring and the long canes¥ are harvested between October and November. By this time they have accumulated part or all of the chilling requirements. The canes are sorted into three, four and five foot batches and transported to southern Spain where they are placed in cold storage (4°C) for 2-6 weeks to complete their rest requirements. After this they are transplanted into unheated 30 feet wide plastic tunnels, at a cane density of 12,000 canes per acre.

High quality early fruit production begins as early as March. Fruit is shipped in refrigerated trucks throughout Europe. Return for the grower on early production is about $25/kg, in March prices drop to $10/kg. After harvest, plants are removed and preparations are made for the planting of a new crop in the fall. Plants from a current greenhouse crop may be used for the next year¥s planting, provided that an adequate bud differentiation has been achieved followed by a cold treatment (6-8 weeks).

Greenhouse raspberry production in the PNW

An experiment was carried out at the PARC Agassiz greenhouse research range to produce raspberries during the winter months. Root cuttings of five raspberry varieties: Chilliwack, Kitsilano, Malahat, Qualicum and Tulameen were planted early in the spring into 1-Gallon pots filled with peat, compost and perlite (1:1:1 by volume). Plants were grown in the greenhouse and then outdoors. Plants were irrigated and fertilized with 14-14-14 Osmocote and biweekly with 3gm/l. solutions of 20:20:20 N:P:K fertilizer . When dormant, the plants were sorted by size into three groups to achieve even plant size for the three dates when plants were moved to the greenhouse. Plants were brought into the greenhouse from outdoors on December 20, January 10 and January 31 after receiving chilling of 750, 1238 and 1602 hours below 4°C respectfully by these three dates.

The greenhouse environment was regulated to maintain 22/17°C day/night temperatures. In the greenhouse plants were lined up in double rows 1.45 m between centres and final plant spacing of 6 pots/m². Plants were irrigated with trickle irrigation and fertigated as needed, the plants were trained with bamboo canes, excessive primocane growth early in the season was pruned. Data was collected on flowering dates, harvest dates, yield and fruit sizes.

To ensure pollination, the first group of plants was hand pollinated with a paintbrush twice a week (January 31 to February 24). Hand pollination required lots of labour, some crumbly fruits were observed as result of poor pollination only in the first harvest date. Bumblebees were introduced in the end of February. To prevent damage to the flowers, bumblebees were let out of their hive twice a week for half a day only. We observed that from over foraging the bumblebees caused some browning to the anthers and the filament (an anther stalk). However, fruit set was very good and the damage did not affect fruit set and yield. Bumblebees proved to be an excellent pollinating insect for raspberries.

Insects and mites had to be monitored regularly. Biological control had to be used because of the presence of bumblebees in the greenhouse. Early insect detection is important for effective control. Since dormant canes were brought from the outside, insects and mites found their way to the greenhouse with them. Aphids, leafrollers, spider mites and slugs had to be controlled. Diseases were not a problem except on one treatment where five years old crowns with their canes were dug out from the field in January planted in 5 gallons pots and moved into the greenhouse. Some canes died of Phytophthora fragariae root rot induced by transplanting plant stress and the damage to the root system. This method of transplanting old canes is not recommended. Transplanting one or two year old field grown plants to the greenhouse might be possible, just like the production method in Spain.

When dormant raspberry plants were moved to warm greenhouse environment between December 20 and January 31 they flowered in 26 to 46 days, and harvest started in 56 to 81 days (Table 1). Because of the short days and low light level during the winter months, plants from the first two dates were slower to flower and ripen by 7 to 15 days than those from the third date. Malahat was the first variety to flower and to ripe at all three dates, producing fruit on February 27. Because of the uneven plant size, average and top yield data are presented. Top yield, represent the yield harvested from the best cane and suggest a yield that can be obtained when good plant growth is achieved during the outdoor growing phase. Malahat produced the lowest yields per canes on all three dates. Because of its lower number of laterals per cane, it might be possible to plant it at a higher plant density than the other varieties. Tulameen had the largest berry size among all the varieties. It produced a high yield with excellent quality and flavour and over all was the most suitable for winter greenhouse production.

Additional reading:

Winter raspberry production in greenhouses. Marvin P. Pritts, Robert W. Langhans, Thomas H. Whitlow, Mary Jo Kelly, and Aimee Roberts. HortTechnology 1999, 9(1)13-15.