Grow tubes reduce root and crown growth but not early production during establishment of highbush blueberry

Authors: STRIK, BERNADINE - Oregon State University; BULLER, GIL - Oregon State University; Tarara, Julie

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/22/2014
Publication Date: 5/1/2014
Citation: Strik, B.C., Buller, G., Tarara, J.M. 2014. Grow tubes reduce root and crown growth but not early production during establishment of highbush blueberry. HortScience. 49:581-588.

Interpretive Summary: Grow tubes are cylindrical plastic shelters that are placed around young trees and vines to protect them from deer browsing, wind, and chemical applications. There is new interest in using grow tubes to establish blueberry bushes, but there is very little information on how the environment inside the tube affects growth of the blueberry bushes. We put grow five different types of grow tubes around new blueberry plants. At the end of the bushes' first year in the field, we removed the tubes and measured the growth pattern of the plants. The tubes reduced the amount of roots and the wood at the base of the plant. Fewer leaves were produced on the 'tubed' plants when they were inside the tubes. There were fewer new shoots on the plants that were in the grow tubes. More leaves were produced by the 'tubed' plants once the plant tops had grown above the height of the tube. The 'tubed' plants were taller and more upright than the plants grown without tubes. Blueberry growers will have to consider the cost of the tubes, the labor required to install and remove them, and whether a tall, upright young blueberry bush is more desirable than a shorter, more prostrate bush.

Technical Abstract: In blueberry, grow tubes have been used by some growers to establish new plantings and to replace plants within older plantings. We conducted two experiments at a commercial northern highbush blueberry (Vaccinium corymbosum L.) farm over three years using four cultivars (Aurora, Elliott, Liberty, Ozarkblue) and five grow tube treatments (no tube, control; translucent plastic; opaque plastic; opaque cardboard; and a wire mesh tube). In one experiment, grow tubes were left on for up to two growing seasons. The impact of tubes on plant biomass allocation and early fruit production was assessed. The presence of a grow tube from spring to fall of the first growing season decreased crown dry weight (DW) and root DW (all except translucent plastic) and increased shoot:root relative to the control. Plants grown in tubes were taller, had a narrower canopy, and fewer whips/plant, likely a response to low light levels inside the tubes; the fewest whips were found in the opaque plastic or cardboard tubes and the most in the translucent plastic tube with an intermediate response in the wire mesh tube. Removal of grow tubes during the summer led to plant damage from sudden sun exposure and is not recommended. The opaque grow tubes (present in year 1) reduced yield/plant of ‘Elliott’ and ‘Liberty’, but not ‘Aurora’ in year 2 (the second growing season). Plants that had a plastic grow tube on for two growing seasons still had reduced whip growth but had greater 1-year-old shoot DW in ‘Aurora’ and ‘Liberty’; however, the greater shoot growth did not increase yield in year 2. Pruning plants to allow for limited early fruit production (~ 0.6 kg/plant) in year 2 did not reduce yield in year 3 (~ 2.8 kg/plant). While grow tubes reduced root and crown growth in the first season, there appeared to be no longer-term adverse effect on above-ground plant growth or yield. Grow tubes, particularly translucent plastic tubes may be used to reduce browsing from vertebrate pests, facilitate spot application of contact herbicides, and reduce damage from wind during the establishment year.