The ‘Columbia Giant’ thornless blackberry is a notable cultivar developed by the U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS) and Oregon State University. It is recognized for its high productivity, large fruit size, and absence of thorns, making it desirable for both home gardeners and commercial cultivation. Its impressive yields and ease of harvesting are primary appeals.
Understanding Columbia Giant Thornless Blackberry
The ‘Columbia Giant’ blackberry is characterized by its trailing growth habit, with vigorous, thornless canes reaching up to 6 feet in height when grown on a trellis. The fruit itself is remarkably large, with some berries measuring up to 3 inches long and averaging around 12 grams.
‘Columbia Giant’ berries possess a balanced flavor profile, combining sweetness with a pleasant tartness. Their firm texture, consistent black color, and glossy appearance make them appealing for fresh consumption and processing. This cultivar also exhibits good resistance to pests and diseases.
Site Selection and Planting
Selecting an appropriate site is important for ‘Columbia Giant’ thornless blackberries. These plants thrive in full sun exposure, ideally receiving at least 6 to 8 hours of direct sunlight daily for optimal fruit production. Shadier locations can result in reduced yields and poorer fruit quality.
Blackberries prefer well-drained soil that is rich in organic matter. An ideal soil pH range is between 5.5 and 6.5, though they can tolerate a range from 5.5 to 7. Before planting, conduct a soil test and incorporate compost or well-rotted manure to improve soil structure and fertility. Space individual plants 4 to 6 feet apart within the row, with rows 10 to 12 feet apart. Dig a planting hole twice as wide as the root ball and of similar depth, ensuring the top is level with the surrounding soil. Thoroughly water newly planted blackberries to settle the soil and eliminate air pockets.
Ongoing Care and Maintenance
Consistent watering is important for ‘Columbia Giant’ thornless blackberries, especially during dry periods and as the plants establish. Provide 1 to 2 inches of water per week, delivered deeply at the base of the plants. Applying a layer of organic mulch, such as straw or wood chips, around the plant base helps conserve soil moisture, regulate soil temperature, and suppress weed growth.
Fertilization supports vigorous growth and fruit production. In early spring, apply an all-purpose fertilizer, such as a 10-10-10 or 16-16-8 blend. For established plants, approximately 1.5 ounces of nitrogen per plant or 3 ounces of nitrogen per 10 feet of row can be applied annually, split into two applications: one in late March to early April and the second about six weeks later.
‘Columbia Giant’ blackberries require trellising to support their trailing canes and facilitate harvesting. Common trellising systems involve setting up sturdy posts with multiple wires. A typical setup might include a bottom wire at 1.5 to 3 feet above the ground and an upper wire at 5 to 6 feet. As new primocanes (first-year canes) grow, they should be trained and tied loosely to these wires to prevent them from sprawling and to optimize sunlight exposure.
Pruning is an annual practice for maintaining plant health and maximizing fruit yield. ‘Columbia Giant’ is a floricane-fruiting variety, meaning berries develop on second-year canes (floricanes). After floricanes have fruited in mid-summer, they will die back and should be cut to the ground. This removal directs the plant’s energy towards developing new primocanes for the following year’s crop. During the growing season, primocanes can be tipped (pruned at the terminal end) when they reach about 30 inches to encourage lateral branching, which increases potential fruiting sites. Lateral branches can be pruned back to 12-18 inches in winter or early spring before new growth begins.
Harvesting and Expected Yield
‘Columbia Giant’ blackberries typically ripen in early to mid-July. The berries are ready for picking when they have developed a deep, uniform black color and detach easily from the plant with a gentle tug. Ripe berries will feel firm but yield slightly to pressure. Harvesting should occur regularly, every few days, during the ripening period to ensure the highest fruit quality and encourage further production.
A mature ‘Columbia Giant’ plant can produce 10 to 15 pounds of fruit annually, making them a rewarding choice for home gardens. After harvesting, berries are best handled gently to avoid bruising, which can shorten their shelf life. Prompt cooling of the berries after picking helps maintain their freshness and quality.