Cooperative Extension Service 
Institute of Food and Agricultural Sciences
Hendry County Extension, P.O. Box 68, LaBelle, Florida 33975-0068  Phone (863) 674-4092

Hendry County Horticulture News

Blackberries - A Luscious Home Grown Treat

Blackberries are a luscious treat that is well adapted and easy to grow in our area.  There are several species of blackberries, all in the genus Rubus.  Native species and commercial plantings extend from Florida to the Pacific Northwest.  Cultivars differ as to winter chilling requirement and susceptibility to diseases.  Proper cultivar selection is important for successful production. Blackberries include both erect and trailing types and are referred to as erect blackberries and dewberries, respectively.  The recommended varieties for Florida are: 'Oklawaha' and 'Flordagrand,' early fruiting trailing types, and 'Brazos,' a later fruiting, semi-erect type.

A blackberry is composed of many drupelets, each of which develops from a single pistil. To obtain a large, well formed berry, most of the pistils must be effectively pollinated. 'Brazos' does not require cross-pollination.  'Oklawaha' and 'Flordagrand' do not set fruit with their own pollen but produce well formed berries when cross-pollinated.

The blackberry is adapted to a wide range of well drained soils.  A pH 5.5-6.5 should provide optimum growing conditions on mineral soils.  A site with good air drainage and frost protection is especially important for the early blooming, trailing types.  Mature blackberry plants are seldom damaged by cold; however, damage to flowers and young fruit is sometimes a problem in years when a late frost occurs.

The cool months are best for setting blackberry plants.  Plants of trailing varieties may be spaced 5 - 10 feet apart in the row between posts that are 20 - 40 feet apart.  The spacing between rows is often 10 - 12 feet, but optimum spacing depends largely on the method of cultivation to be used.  Set plants of the semi-erect 'Brazos' 4-6 feet apart in the rows.  A forty foot bed of blackberries will provide a generous harvest for a family of four.

For easy picking, and cleaner fruit, the canes should be trellised. When vigorously grown and properly pruned, the 'Brazos' requires no trellis; however, 'Oklawaha' and 'Flordagrand' require a trellis. There are a number of trellising methods. A common one consists of three evenly spaced horizontal strands of wire with the top one 5 feet high. The wire is supported by well anchored end posts with smaller posts within the row.

It is best to tie at least one new cane to the top wire. Later developing canes can then be drooped
over the wires, but not sharply bent. Thorns tend to hold the additional canes on the trellis without being tied.

Weed control is important in establishing and maintaining a vigorous and highly productive blackberry planting. If the plantings were made during the late fall or winter, no additional fertilizer need be applied until late February or early March when 1/5 pound of a mixed fertilizer (i.e., 8-8-8) should be applied per plant. Repeat at 8-10 week intervals until early September. During all succeeding years, make 3 applications of 1/3 pound mixed fertilizer per application. Make applications in February, June and late August.

Because of variations in frequency and amount of rainfall, irrigation is necessary for successful blackberry production.  In general, 1 inch of water per application is sufficient. Irrigation is needed at weekly intervals during the dry periods of late spring and early summer.

Unlike most other fruit plants, the blackberry has perennial roots with biennial tops- tops which grow one summer and produce fruit the next spring. Fruiting canes die after harvest and are of no further use in the planting. Because of the long growing season in Florida, the general practice has been to remove all tops to ground level immediately after harvest. The brush that results
harbors insects and diseases and should be burned. An easy method is to chop the vines down low and use a lawn mower to cut the plants down to ground level.

Blackberry plants will normally propagate themselves throughout the summer by root suckering and natural layerage. Blackberries can also be propagated from leafy stem cuttings.  Cuttings can be obtained from an established plant by using the new canes while their growth is still tender. Make cuttings 4 - 6 inches long, and insert them 1½ to 2 inches into the rooting media. A ½ perlite and ½ peat mixture provides a well drained, sterile medium suitable for good rooting. Rooting usually occurs within 5 - 6 weeks.

Trailing types can also be propagated in the summer by covering new cane tips from established
plants with soil. The rooted tips are dug and planted before the following spring.  All blackberry varieties will propagate from root cuttings although this method is most often used with the 'Brazos' types. Pencil size root cuttings are most likely to produce a strong vigorous plant.  Sucker plants growing from roots may also be dug and planted. The 'Brazos' types sucker more
readily than the trailing types, making it possible to obtain a considerable number from one plant.

Several insects and diseases may attack blackberries.  Fungal diseases that commonly appear on blackberries include anthracnose, leaf spot, and rosette.  Good cultural practices and sanitation including cutting back old and new canes after harvest will prevent most diseases.  Insect control is not regularly needed in most areas.  Occasional severe infestations may warrant chemical control.

The harvest season for 'Oklawaha' and 'Flordagrand' occurs in March - May, varying by year and location, and lasts approximately one month. 'Brazos' ripens later, thus prolonging the harvest season in a given area. Blackberry fruits bruise easily and are extremely perishable. They should be handled with care when harvested and used immediately.  Blackberries are a welcome treat, coming at a time when few fruits are in season.  Their adaptability, prolific nature and high price in stores make blackberries a good choice for the home garden.  Good luck and good gardening.

Gene McAvoy is the horticulture agent with the Hendry County Extension Service.  Direct your horticulture questions to PO Box 68, LaBelle, FL 33975,  e-mail - or phone 863-674-4092 or 863-983-1598.  You are also welcome to visit the Hendry County Extension Office at 225 Pratt Blvd., LaBelle.   Office hours are from 8:00 - 5:00.

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