May is harvest time for blackberries in northeast Florida!  All through April we’ve been enjoying the beautiful flowers.  We’ve watched the fruit, made up of multiple clustered drupelets, develop.  Now, for the next month or so, it’s harvest time!

Wild, native blackberries grow throughout northern Florida, and people have harvested them for centuries.  You can still find native species and grow them.  But the plants are thorny, the berry size is small, and the flavor is pretty tart.  Backyard gardeners now have many cultivated varieties to choose from that are thornless, sweet and productive.

Where should I plant blackberries?

Blackberries do best in well-drained soil with a pH between 5.5 and 6.5.  (If you’re not sure of your soil pH, learn how to take a sample and bring it in to the UF IFAS Extension Duval County office at 1010 N. McDuff Ave. and get it tested for free!)  Plant them where they will get full sun and good air circulation.  Be sure to factor in space for a trellis and access to water for irrigation.  Use drip irrigation rather than overhead irrigation if possible.  Drip provides needed water to the blackberry plants without watering nearby competing weeds.  You can set up the irrigation system before planting.

Blackberries are well-suited to USDA hardiness zones 5-9.  Although some varieties can be grown as far south as central Florida, blackberries need winter chilling hours in order to produce flowers and fruits the following spring.  What are chilling hours?  Simply the number of hours between 32- 45 degrees F. in an area over the cool season.  For us in Duval County, the average is 300-500 per year.  But remember, this number can vary significantly from year to year and from one part of the county to another.

Which variety should I plant?

Researchers at the University of Arkansas have taken the lead in producing cultivated varieties for the Southeast.  Many of them are named after Native American tribes that inhabited that region.  And despite our distance from Arkansas, some of them grow well here in coastal northeast Florida.  UF IFAS scientists evaluated seven of them at the Gulf Coast Research and Education Center in central Florida.  Some that performed well there and that have no more than 500 required chilling hours are ‘Ouachita,’ ‘Osage,’ and ‘Prime-Ark Freedom.’  All are thornless and have good fruit quality.  See ‘Choosing the Right Blackberry Cultivar in Subtropical Florida‘ for more details.  UF IFAS researchers are working with these and other cultivars to develop varieties for Florida ad beyond that have even more antioxidant and anti-inflammatory compounds and that are tastier and more disease resistant.  So, stay tuned for these future varieties!

Blackberry Fruiting Types

Blackberries have two types of stems, or canes, on the plants.  First-year canes, called primocanes, have only leaves.  They continue growing until the plant goes dormant in the winter.  After the plant breaks dormancy in the spring, they become able to develop flowers and fruits, and they are called floricanes.  Once they flower and fruit, the floricanes die.  Ouachita and Osage, mentioned above, are both floricane-fruiting cultivars.  Prime-Ark Freedom and others like it, in contrast, bear fruit on primocanes, and are theoretically capable of having two crops in one year.  Berries can form on primocanes in late summer, and then on floricanes the following spring.  In Florida, however, the primocane fruits in late summer are typically poor in quality and yield because our extreme summer heat damages flowers.

Taking Care of Blackberry Plants

Growing blackberry plants is not particularly difficult or time-intensive, as long as you follow a few essential practices.

•  First, prepare a trellis to support the blackberry canes.  Blackberry plants are either erect, semi-erect or trailing, but all benefit from support.  For homeowners, this may be as simple as posts with wire or lattice, but there are many other options.  See the UF IFAS publication ‘How to Build a Blackberry Trellis System:  A Complete Guide‘ for more details. 
• Second, plant blackberries while they’re dormant–from December to February.  When planting, be sure the roots don’t dry out, cut the shoots to about 6 inches long, and plant at the same depth as the plant was in its container.  In general, plant spacing is 2-5 feet but varies by cultivar. 
• Third, don’t over fertilize.  Blackberry roots are close to the surface and can be burned or killed by excessive fertilizer.  Don’t fertilize at planting; wait until late spring or summer to fertilize with 10-10-10 NPK with micronutrients in an 18-inch ring around the plant.  Thereafter, fertilize in winter and summer.
• Fourth, control weeds.  You can do this by mulching, cultivating, mowing or applying herbicides.  When weeding or cultivating, try not to disturb soil more than 2 inches deep.  Blackberry roots are shallow and can be easily injured. 
• Finally, know whether your particular cultivar is self-fruitful or not.  Bees pollinate flowers, but some varieties require a pollenizer, or another blackberry variety nearby, in order to form fruit well.  All the Native American tribe named Arkansas varieties are self fruitful and do not require a pollenizer.

Training and Pruning Blackberry Plants

Blackberry plants are perennial and may live for many years.  They are most productive for 4-7 years in Florida.  To keep them healthy and productive for as long as possible, pruning is essential.  It removes old floricanes, keeps fruit off the soil, promotes flowering and fruiting and keeps canes from crossing and hindering each other.  For details on what to do, how to do it and when, see the UF IFAS document ‘Floricane Blackberry Pruning Guide for Florida.’

Harvesting and Enjoying Your Blackberries

Berries are purple-black and glossy when ready to harvest.  Pick by hand in the early morning when it’s cool, and refrigerate the berries immediately.  Wait until you’re ready to eat them to wash.  Picking a couple times a week should keep you ahead of the birds and other critters.  If you don’t have blackberries at home this year, you can plan and prepare for next year.  Or, check out the website UPickFarmsUSA.  It has listings of counties with farms where u-pick blackberries are available in Florida.

Try growing blackberries–a tasty, healthy and relatively carefree fruit crop–in your northeast Florida home garden!

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