|Author: ||M.P. Pritts|
|Keywords: ||primocane, floricane, trellising, winter injury|
Blackberries are impractical to grow in the northeastern US on a large scale because cold winter temperatures are experienced regularly and the overwintering upright canes are frequently injured.
Four-season high tunnels built to withstand a snow load can provide sufficient winter protection for thornless blackberry cultivars in most years.
Yields of mature blackberry plants under tunnels can be very high, and approach yields obtained in the very best outdoor climates.
One of the greatest challenges to high tunnel blackberry production is the excessive primocane growth during the summer.
Plants set at a standard plant spacing (1.2 to 1.8 m in row and 2.3 to 2.5 m between row centers) will quickly fill the available space and make it difficult to traverse down the rows for spraying or harvesting. 'Triple Crown' blackberries were planted at half the standard density (2.3 m between plants) and trellised with just two primocanes per plant trained horizontally along a low wire on one side of a V-trellis.
When these canes reach the adjacent plant, the growing tips are removed and the primocanes produce laterals that are then trained vertically to one side of the V-trellis.
Additional emerging primocanes are removed.
This system markedly reduces the amount of vegetative growth and greatly facilitates harvest.
In the first fruiting year (2013), yields between the low density plots and high density plots were not significantly different.
The following year (2014), temperatures went below -17°C on 19 different occasions with two periods of rapid temperature change.
All of the canes experienced severe damage, resulting in no blackberry fruit in tunnels for the first time in 8 years.
Consistent production may require the use of heaters on nights when the outside temperature drops rapidly or falls below -20°C. Regardless, blackberry production in tunnels appears to be economical, even with occasional years when production may be compromised by cold winter temperatures.
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