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Managing Weeds in Organic Blackberry Production

Thursday, January 30, 2014   (0 Comments)
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Weed mat determined to be more cost effective than hand weeding

CORVALLIS, OR--Blackberries in all forms are becoming more popular with consumers. More than half of the blackberries in the United States are processed fruit (individually quick frozen, bulk frozen, puree, freeze-dried, canned, juice, and juice concentrate), produced primarily in Oregon. With significant expansion in organic plantings expected in the next 10 years, commercial growers are looking for effective and low-cost weed control methods for their blackberry operations.

According to the authors of a study published in HortScience, a few commercial operations grow organic blackberries with no weed control and achieve reasonable yields, but weeds left uncontrolled may interfere with machine harvest and produce seeds that become fruit contaminants. Renee Harkins and Bernadine Strik, from the Department of Horticulture at Oregon State University, along with David Bryla from the U.S. Department of Agriculture/Agricultural Research Service, evaluated the effects of three different organic weed management strategies on growth and early production of trailing blackberry.

The team investigated three treatments: non-weeded plots, where weeds were cut to the ground just before harvest; hand-weeded plots hoed two to three times per year; and weed mat plots covered with black landscape fabric. Each treatment was fertilized with OMRI-approved fish emulsion and drip irrigated. Blackberry plants in each treatment were drip irrigated under the weed mat. Two popular trailing blackberry cultivars, 'Marion' and 'Black Diamond', were used for the study. "Both of these cultivars are predominantly harvested by machine for high-value processed markets and together accounted for greater than 75% of  the blackberries produced in Oregon in 2012," the researchers said.

The researchers determined that weed mat led to the highest yield and net returns across the treatments. "Of the three practices studied, weed mat was best suited to organic production of blackberries. The initial cost of the weed mat was far less than the cost of hand-weeding during the first 3 years after planting, and after only one season of fruit production, the yield benefit of weed mat provided enough profit to warrant its use over no weeding or hand-weeding," they said. The experiments also showed that both 'Black Diamond' and 'Marion' appeared well suited to organic production in the present study.

"The results of our study indicate that weed control is beneficial during establishment of trailing blackberry and can be done successfully in organic plantings using hand-weeding or weed mat," the authors said. The team plans to continue the research for at least 3 more years to determine the sustainability of each practice.

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The complete study and abstract are available on the ASHS HortScience electronic journal web site:

Founded in 1903, the American Society for Horticultural Science (ASHS) is the largest organization dedicated to advancing all facets of horticultural research, education, and application. More information at

Original Article:

Weed Management Practices for Organic Production of Trailing Blackberry: I. Plant Growth and Early Fruit Production
Renee H. Harkins, Bernadine C. Strik, and David R. Bryla

HortScience 48:1139-1144. [Abstract]

Corresponding author. E-mail: