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March 4, 2021

Arkansas Agricultural Experiment Station releases new primocane-fruiting blackberry

By Fred Miller
U of A System Division of Agriculture

Fast facts

  • Prime-Ark® Horizon offers growers new option for primocane-fruiting blackberries
  • Thorny variety offers high yield potential
  • Now available for non-exclusive licensing to propagators

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CLARKSVILLE, Ark. — Prime-Ark® Horizon, a new primocane-fruiting blackberry from the Arkansas Agricultural Experiment Station, offers growers a new option with an extended fruiting season and high yield potential.

Arkansas Blackberries
HIGH YIELD — Prime-Ark Horizon is the sixth primocane-fruiting blackberry variety released by the Arkansas Agricultural Experiment Station. It is noted for high yields and an extended primocane fruiting season. (UA System Division of Agriculture photo by Fred Miller)

Prime-Ark® Horizon is a thorny variety and the sixth primocane-fruiting blackberry from the experiment station’s fruit breeding program. Experiment Station fruit breeders have released 21 public blackberry varieties since James N. Moore began the program in 1964.

Blackberry plants produce biennial canes that have a lifespan of two years, said John R. Clark, Distinguished Professor of horticulture and fruit breeding for the Arkansas Agricultural Experiment Station, the research arm of the University of Arkansas System Division of Agriculture. Most blackberries flower and fruit on the second-year canes, known as floricanes. Harvest date for floricane blackberries on Prime-Ark® Horizon averaged about June 12 at the Division of Agriculture’s Fruit Research Station near Clarksville.

Primocane fruiting blackberries flower and bear fruit in spring or early summer on those floricanes, Clark said. They then flower and fruit on the first-year canes, or primocanes, later in the summer. For Prime-Ark® Horizon, the first harvest on primocanes begins about Aug. 4 and extends to as late as mid-October.

“That’s a fruiting period of over 60 days, which is longer than any other primocane-fruiting variety from our breeding program,” Clark said. “Prime-Ark® Horizon just fruits longer, and that makes for a nice extended picking season for Arkansas growers.”

Clark said Prime-Ark® Horizon makes an excellent complement to Prime-Ark® 45, which has similar postharvest potential and ripens about six days earlier.

Prime-Ark® Horizon’s floricane berry crop has high yield potential, exceeding 30,000 pounds per acre in some years, Clark said. He advises pruning to control the harvest and to balance the yield between floricanes and primocanes. A very large floricane crop can also lead to smaller leaf size and upward leaf curling on floricanes, which can hurt plant health, he said.

The primocane yields at the Fruit Research Station ranged from 3,000 to 9,000 pounds per acre.

Berries average 7.8 grams overall, Clark said, and floricane berries can get as big as 10 grams. Primocane berries average 7.3 grams. Prime-Ark® Horizon berries have good flavor with light aromatics, though they can be tart, especially when floricane yields are high.

Postharvest storage for seven days has been comparable to Prime Ark® 45 for reversion, a postharvest disorder in which black drupelets revert from fully black to a reddish color, Clark said. The berries retain excellent firmness. Leakage and decay are minimal, measuring among the best in the Arkansas program.

Prime-Ark® Horizon plants have shown good health, except when floricane yields were excessive. Clark said he observed no orange rust or anthracnose on the plants, and they showed very little winter damage in temperatures down to 1 degree Fahrenheit.

More information about Prime-Ark® Horizon is available online:

Prime-Ark® Horizon is available for licensing to propagators. Contact Cheryl Nimmo for licensing information at 479-575-3953 or by email at

Clark said he and breeding colleague Margaret Worthington, assistant professor of horticulture, have more exciting primocane and floricane blackberries in the pipeline as they continue to develop improved varieties.

To learn more about the Arkansas Agricultural Experiment Station fruit breeding program, visit the program’s website:

To learn more about Division of Agriculture research, visit the Arkansas Agricultural Experiment Station website: Follow us on Twitter at @ArkAgResearch and Instagram at ArkAgResearch.


About the Division of Agriculture

The University of Arkansas System Division of Agriculture’s mission is to strengthen agriculture, communities, and families by connecting trusted research to the adoption of best practices. Through the Agricultural Experiment Station and the Cooperative Extension Service, the Division of Agriculture conducts research and extension work within the nation’s historic land grant education system.

The Division of Agriculture is one of 20 entities within the University of Arkansas System. It has offices in all 75 counties in Arkansas and faculty on five system campuses.

The University of Arkansas System Division of Agriculture offers all its Extension and Research programs and services without regard to race, color, sex, gender identity, sexual orientation, national origin, religion, age, disability, marital or veteran status, genetic information, or any other legally protected status, and is an Affirmative Action/Equal Opportunity Employer.


Media Contact: Fred Miller
U of A System Division of Agriculture
Arkansas Agricultural Experiment Station
(479) 575-5647