Cranberries are a great groundcover, and they can also produce abundant fruit harvests. One pound (0.5 kg.) of fruit from every five square feet (0.5 sq. m.) is considered a good yield. If your cranberry plants are producing few or no berries, there are several possibilities you’ll need to consider.
Why Won’t My Cranberry Fruit?
A cranberry vine with no fruit may simply be too young. Cranberry plants are most commonly available for purchase in two forms: one-year-old rooted cuttings and three- or four-year-old plants. If you plant cuttings, you will have to wait about three to four years to get fruit. If you transplant older plants into your garden, you may get a small amount of fruit the same year you plant, and you should get a full harvest by the third year.
A second consideration is the number of uprights. When cranberries are first planted, they’ll produce trailing runners that help the plants cover the ground. Then, after two or three years, the runners will begin producing upright shoots. The flowers and fruit appear on these “uprights,” so with more of them- up to 200 uprights per square foot (0.1 sq. m.)- you’ll get more fruit.
A third potential reason you might have no fruit on a cranberry vine is poor pollination of the cranberries. Bees, including honey bees, bumblebees, and other wild bees are responsible for cranberry pollination. Cranberries are not the bees’ favorite flower, since they contain less nectar than many others, so you’ll need a higher population of bees than you would for more attractive plants. Renting a hive is a good idea for large plantings.
What to Do for a Cranberry Not Fruiting
A cranberry vine with no fruit might need better pollination. If your plants are producing flowers but little fruit, you may need to attract more pollinators to your garden.
Nitrogen fertilizer will encourage cranberries to produce runners at the expense of upright growth. Cranberries are adapted to low-fertility sites and don’t typically need fertilizer for several years or more. Avoid fertilizing with nitrogen in the first two years, and only feed with small amounts of nitrogen after the second year if the runners do not seem to be covering the ground effectively. Older cranberries may eventually need a boost from liquid fish fertilizer.
If left alone, a cranberry patch will continue expanding by producing more runners and fewer uprights. If you have no fruit on a cranberry vine, try trimming back some of the runners around the margins. This measure will encourage your plants to settle down and produce more uprights and, therefore, more fruit.
Sometimes, conditions that lead to a cranberry not fruiting are out of your control. Each upright should have 3 to 5 flowers. Uprights with few or no flowers are a sign that harsh weather from spring through fall damaged the flower buds. In that case, production should be back on track the following year.