Michael Polozola

One of the most common pitfalls in blackberry cultivation is allowing the planting to become unmanageable. Many growers struggle with pruning, and before long, their blackberry patch turns into an overgrown, diseased mess. The Trellised Production Using Primocane Suppression (TPUPS) technique offers an innovative solution. This method simplifies the harvesting process, significantly reduces disease pressure and makes growing thorny selections less of a prickly affair. Inspired by the success of horticulturist Arlie Powell of Alabama, whose Kiowa blackberry plants have thrived for more than 25 years using this method, early trials at the LSU AgCenter Dean Lee Research and Extension Center are showing promising results. This longevity is notably longer than the typical lifespan of commercial blackberry plantings, which generally last around 10 to 20 years.

The benefit of the TPUPS method is that by suppressing primocanes (the first-year growth of blackberry plants) until late in the season, more sugars are dedicated to fruit production, making the plants easier to manage and harvest. If disease issues do arise, the plants are easier to spray. Less bushy growth makes the fruit easy to pick.

Setting Up the Trellis System

All blackberries benefit from being grown on a trellis system, which helps keep plants manageable and easy to harvest. The range of trellising options varies from casual cattle panels (gridded fence panels) to comprehensive commercial setups. One of the perks of the TPUPS method is that it utilizes a trellising system that is economical for commercial growers and easy to install for residential homesteads. However, it is worth noting that this method can be more labor-intensive than other trellising systems.

The TPUPS method uses a setup nearly identical to what is called an I-trellis, with wires positioned at 3 and 5 feet. The primary difference from the standard I-trellis is that canes are trellised on the wire more intensely, akin to grape production, rather than just providing support for upward-growing canes. To set up this system, growers will need sturdy posts, high-tensile wire and tensioners. Posts should be placed at regular intervals to support the weight of the plants, but fewer posts are needed compared to other systems because the plants are retrained every year, preventing a large mass buildup.

Spacing of the plants in this system is farther apart than in traditional blackberry cultivation due to the differences in the trellising techniques. Plants should be about 5 to 6 feet apart to maximize the fruiting area, which extends more horizontally than vertically.

Primocane Suppression Techniques

Timing and Methods: The crucial part of the TPUPS method is training the plants properly from the start. It is important to begin with vigorous plants. The first year should focus on plant establishment, especially if starting from freshly rooted plants. In year two, or later in the first season, primocanes (fresh growth from that year) should be selected and trellised on the wire. Floricanes (second-year growth) must be pruned out every year, as they typically decline in vigor significantly in late June and July and eventually die, making them easy to identify for removal.

Another critical aspect of the TPUPS method is primocane suppression. For established plants, primocanes attempting to emerge from January to late May and early June need to be pruned off. This task must be performed several times a month. Primocanes are only allowed to come up later in the fruiting season (June to July) to train replacements for the next year. Only two primocanes will be selected, one for the 3-foot wire and another for the 5-foot wire. It is important to do this process early, as a delay can lead to stunting if too many resources are spent on primocanes that are eventually pruned out.

Weeds are easy to manage in a TPUPS system through either conventional or organic methods. Because the plantings are managed without unrestrained primocane growth, they are easy to spray or maintain weed-free through mechanical means. Disease and insect management can be either preemptive or on an as-needed basis, depending on the goals of the planting. Commercial operations should consider a few applications of fungicides throughout the season, either organic or conventional, to prolong the longevity of the planting.

Plants will be much more vigorous and fruitful with proper irrigation. Fertilization is also important in maintaining vigor and production. Regular soil testing is recommended for commercial operations, but homeowners can fertilize with 0.25 pounds of nitrogen or 2.5 pounds of 10-10-10 fertilizer per plant.

Benefits: Primocane suppression leads to larger fruit that is easier to harvest because primocanes are not in the way. Additionally, disease pressure is greatly reduced in this system, especially viral diseases, leading to increased lifespan potential for the planting. It is not unusual for other cultivation methods to need replacement every eight to 10 years, while a Kiowa planting using the TPUPS method has been reported to thrive for at least 25 years.

Successful Cultivars

Among the blackberry cultivars tested, Kiowa and Ponca have shown exceptional compatibility with the TPUPS technique. These varieties thrive under the trellising system, producing abundant and high-quality fruit. Conversely, not all blackberry varieties are suited for this method. For instance, Caddo has not performed well at Dean Lee and has been removed. Sweetie Pie, introduced a year after Kiowa, Ponca and Caddo, is exhibiting promising results. There has been considerable interest in incorporating a primocane-fruiting blackberry variety into the TPUPS system. Prime-Ark Freedom has been added to answer those inquires.

Conclusion

The TPUPS technique offers a promising approach to blackberry cultivation by addressing common challenges such as disease management and ease of harvest. By adopting this method, growers can potentially increase the lifespan and productivity of their blackberry plantings. With successful cultivars like Kiowa and Ponca, and ongoing trials with new varieties, the future of blackberry farming looks bright. As more growers explore and implement the TPUPS system, the benefits of this innovative technique will continue to unfold, inspiring a new era of efficient and sustainable blackberry production.

Michael Polozola, the AgCenter Extension state fruit and nut specialist, is stationed at the AgCenter Dean Lee Research and Extension Center in Alexandria.

This article appears in the spring 2025 edition of Louisiana Agriculture.

A blackberry plant grows on a trellis built using the Trellised Production Using Primocane Suppression (TPUPS) technique, which simplifies the harvesting process, significantly reduces disease pressure and makes growing thorny selections less prickly. Photo by Michael Polozola

A blackberry plant blooms at the AgCenter Dean Lee Research and Extension Center in Alexandria. Photo by Michael Polozola