Blueberries (Vaccinium spp)

How well established is this crop?

This crop is a relatively new crop. It has been grown here commercially for approximately 5 years. Commercial returns, current growers and some level of regional based research may be available to help those new to this industry.

Background

With a world-wide move back towards healthy eating, blueberries have become hugely popular. Blueberries are very high in vitamins and have high antioxidant properties when compared to many commonly eaten fruits and vegetables.

Once established, they require little management and are naturally resistant to many pests and diseases. New Zealand has an active industry and breeding program giving the grower a large number of selections to choose from. You should consider trial growing to work out the best varieties to grow on your property.

Winter Chilling and Frosts

Blueberry varieties and their chilling requirements can be divided into three groups. Chilling is a measure of the total number of hours required below 7 degrees C from June to August (incl).
Northern Highbush varieties; 700 hours winter chilling.
Rabbiteye varieties; 400-500 hours winter chilling.
Lowbush varieties; 300-500 hours winter chilling.

The hard frosts of a Central Otago winter do not seem to affect the Blueberry bushes growing in a large trial planting at HortResearch in Clyde.

Rainfall and Irrigation

Blueberries do not like drying out, so irrigation is essential especially in inland areas of Otago. This is especially important as the berries near harvest. Blueberries swell dramatically in size in the last few weeks. Dry soils prior to harvest will lead to undersize and poor quality fruit.

Using mulch will reduce the water loss from the soil and mean less irrigation is needed. Drip methods are the best, rather than overhead systems as they deliver water directly to the plants root zone.

Wind

Like most high value crops, shelter from the wind is essential. This can take the form of natural tree shelter or artificial shelter using wind cloth. A
If using natural tree shelter, make sure the shelters running east-west are deciduous. This will allow sunlight into the blocks in the winter. Position all shelters at right angles to the prevailing winds. Talk to your local nursery when deciding on the right tree type for your property. They may also be able to help with design.

Soil

Blueberries have shallow, surface feeding, fibrous roots and require the soil to be moist and free draining if they are to grow well. They also like an acidic soil, with a high proportion of organic matter. Drained peat bogs are ideal for all of this with a pH of around 5.0.

Blueberries can also be grown in mineral based soils but efforts must be made to acidify them and increase the humus (organic mater) content. Additions of mulches such as peat moss, grass, acidic compost, or sawdust will help create these conditions. Growing blueberries in clay soils is not recommended. These dry out in summer and waterlog in winter. Blueberries do not tolerate these conditions.

Fertility

Blueberries are not a quick growing plant and have relatively low nutrient requirements. When adding fertilisers for nutrient deficiencies, you can use formulations that also help with other soil properties as well. For example if the plants need nitrogen, the addition of ammonium sulphate or di-amonium phosphate, will also make the soil more acidic. A useful side benefit. Slow release fertilisers are the best and a ‘less is best’ approach is the good method for the new growers. Blueberries are very susceptible to over fertilising because of the position of the feeder roots near the soil surface.

Weed Control

Perennial weeds are a major problem in blueberry blocks and are best controlled before planting. The bushes grow very slowly and any weed competition will further slow their growth down. Using agrichemicals to control weeds can be damaging because of the close proximity of the feeder roots to the soil surface.

Varieties

A range of varieties are available to the new grower. Contacting an established producer may take some of the guesswork out of selecting varieties suitable for Otago conditions. HortResearch in Clyde have a large trial planting containing many of the following varieties. They may be a good place to start.

Northern Highbush varieties: Puru, Nui, Reka, Duke, Bluecrop, Jersey, Dixie, Elliot
Rabbiteye varieties: Takahe, Whitu, Ono, Rahi, Maru, TifBlue, Powderblue, Delite, Centurion, Southland.
Lowbush varieties; Misty, Marimba, O’Neal.

Rabbiteye varieties do benefit from cross pollination with other varieties. Northern Highbush selections tend to be self fertile (see ‘Layout’ section).

Pests and Diseases

Blueberries are relatively free of pests and diseases. Leafrollers, scale insects and grass-grub do affect the bushes but are easily controlled with insecticides. The main fungal diseases is crown rot caused by Phytophthora. This is controlled if the plants are grown in the right environmental conditions. It seems to be a major problem in waterlogged soils.

Birds can also be a problem and are best controlled by netting the blocks, shooting, or using other means of bird scaring.

Layout

Rabbiteye varieties are usually planted in rows with plants 2m apart within the rows. They benefit from cross pollination so two rows of a certain cultivar within another variety either side, does the best job.

Most Highbush plants are self fertile so can be planted up in larger blocks of a single cultivar. They are also planted out with 2m between the plants within the row.

Both Rabbiteye and Highbush varieties usually have approximately 3m between rows to allow for tractor and harvest access. This allows for a final planted density of between 2500-3500 plants/ha.

General Management

After planting usual mangement will include, mowing, weed spraying fertilising and irrigation. A light prune will help the bush get established. Removing the fruit in the first two seasons is also recommended to help the bush grow vegetatively. After that time an annual prune will make sure wood is renewed on on the bush and it is encouraged to keep growing. Blueberries produce fruit on last season’s growth, so pruning out old and diseased wood is important.

Harvest

Small blocks can be harvested by hand but for larger areas machinery is the best option. Leaving the fruit on the bush to ripen naturally, makes for a better quality berries.

Equipment

Small blocks can be managed with a back-pack spray unit and general gardening equipment. Larger blocks are best managed with a small tractor unit for spraying and grass mowing etc. Specialist harvest machinery will also be needed if you are not going to do the job by hand.

Returns

A healthy blueberry bush is capable of producing between 3-4kg of fruit by the end of its 5th growing season. This could increase to 8-10kg when mature at year 10.

Returns depend on the final use of the fruit. Frozen product reaches $4-5/kg while fresh can return up to $15/kg.

Contacts

If you are thinking of growing blueberries contact HortResearch in Clyde for the latest breeding and variety information on 03 4492 896

For fertility information
http://www.hortnet.co.nz/publications/guides/fertmanual/blue.htm

For plant material contact
Tharfield Nurseries Tauranga. 07 552 5802
Ngaroto Nurseries, Te Awamutu. 07 871 5668