Ferguson: Grow some blackberries for a delicious, sweet treat

Published 12:48 pm Friday, January 14, 2022

Most people have encountered blackberries at one time or another. If your recollection is of thorny plants and small berries, you’re in for a treat. Within the past 30-plus years, plant breeders have released blackberry varieties that lack thorns (or, technically, prickles), have an upright growth habit, and produce large fruit. Many are quite sweet.

If you’d like to try one or more of these varieties in your garden, some to consider are Arapaho, Natchez, Osage and Ouachita. Caddo and Ponca are two of the newest varieties. I’m not aware that they’ve been tried here yet but, like the other varieties mentioned, they have chilling hour requirements compatible with what we typically get here in the Florida Parishes. Ponca is reported to taste especially sweet.

The above varieties produce fruit on second-year canes. This is the traditional habit of blackberries and raspberries: Shoots arise from the base of the plant in the spring of one year but don’t flower and produce fruit until the following year. In the first year of growth, the canes are called “primocanes,” and in the second year, they’re called “floricanes.” (Primocanes typically have five leaflets per leaf, while floricanes have three). After the floricanes produce fruit, they die and should be removed. Meanwhile, the primocanes that have arisen that year are kept and produce fruit the following year.

Some new varieties produce fruit on primocanes, as well. While floricane crops ripen in late spring, fruit produced on primocanes ripens in late summer. Because of the high temperatures that we experience when primocanes are in flower, there is uncertainty about how much of a primocane crop we can reliably produce. Regardless of whether they fruit in the late summer, the primocanes become floricanes and can produce in the spring of the second year, as a traditional variety would. Primocane-fruiting varieties compatible with the winter chilling that we get include Prime-Ark 45 and Prime-Ark Freedom. (Unlike other mentioned varieties, Prime-Ark 45 is thorny).

As with most fruiting plants, plant blackberries in full sun for maximum productivity. Soil should be well-drained and have a pH around 5.5 to 6.5.

Most modern varieties have an erect growth habit and can be planted two to four feet apart within a row. A trellis with wires at two to three feet and four to five feet from the ground can be used to support plants. A single set of wires at the given heights can be used, but a trellising system with two sets of wires running parallel to each other — such that canes are allowed to grow between them — is likely to result in greater fruit production. In such a system, the top two wires can be about two feet from each other (measuring horizontally) and the two lower wires closer.

In the summer, after primocanes have grown higher than the top wire of the trellis, remove the tips of the shoots so that the canes will produce side branches (“laterals”). (It’s best to remove tips while they’re still tender enough that you can pinch them off with your fingers.) In the winter, while the plants are dormant, shorten laterals to one to 1.5 feet long. At that time, also thin out the canes so that there are about six to eight canes per three feet of row.

Keep weeds and grass from growing near the bases of plants. A four-foot-wide weed-free strip is advised. Mulch can be used to help suppress weed growth.

To reduce the chance that diseases and insect pests of blackberry will spread from wild plants to your cultivated ones, it’s recommended that wild blackberry plants growing nearby be removed.

Newly planted blackberry plants can be fertilized when new growth begins in the spring (no sooner than three to four weeks after planting) and again after the spring harvest. Apply 0.5 pound of 10-10-10 (or equivalent) per 10 feet of row. If plants are fertilized individually, spread about three tablespoons of 10-10-10 around each plant, keeping fertilizer at least one foot away from the base.

Blackberries are sweetest when they’ve passed the shiny stage and have a dull appearance. If you’ll be eating the fruit soon after picking it, wait until this dull stage to pick it. If you need to keep it in the refrigerator for a few days, though, pick it a little earlier. Harvest fruit at least twice per week.

Dr. Mary Helen Ferguson is an Associate Extension Agent with the LSU AgCenter, with horticulture responsibilities in Washington and Tangipahoa Parishes. Contact Mary Helen at mhferguson@agcenter.lsu.edu, 985-839-7855 (Franklinton) or 985-277-1850 (Hammond).