Beautiful Spring Blooms Predict Delicious Summer Fruit​

UT Gardens’ Plant of the Month for March 2019:  Blackberries

Submitted by Holly Jones and Carol Reese of the UT Gardens in Knoxville and Jackson, respectively

Blackberries are a good candidate for the home garden. Delicious and nutritious eaten out of hand or cooked, nothing says summer in the south like fresh blackberries. Not only are they great for consumption, but they provide ornamental appeal as well. White flowers resembling small old-fashioned roses appear in late spring, fruits change from green to red to purple black as they ripen, the leaves often show fall color and overwintering canes display interesting shades of red and purple. They are also a good crop for U-Pick orchards and even commercial production but the berries are soft and shelf life is brief, so they can be challenging to harvest, store and sell. 

The common terms brambles and cane fruit refer to all plants in the genus Rubus, which includes blackberries, dewberries, raspberries and boysenberries. The most common growth pattern of brambles is to have roots that are perennial, but shoots that only live for parts of two growing seasons. The first year of emergence these shoots are purely vegetative growth (stems and leaves) and are called primocanes. In the second season of growth, these same stems produce flowers and fruit and are called floricanes. They die at the end of the second season and should be removed. Primocanes emerge in the late spring and grow side by side with the current year’s floricanes. 

Blackberries thrive best on fertile, well-drained soil in full sun. The plants will tolerate part shade but yield and sugar content will be diminished. Periods of high rainfall or overzealous irrigation during the ripening phase can also lead to a less sweet crop. While easily grown, they can become a management challenge if not maintained. It is their nature to sprawl and growth is rapid so consider a trellising system and a regular pruning regime to remedy what can quickly become a blackberry jungle. Erect and semi-erect types of brambles may only require some tip pruning and heading back to keep vines from covering too much garden space and hindering harvest, but trailing types benefit most from trellising to get the fruit off the ground. Pruning tips and trellising systems are addressed thoroughly in this publication from the University of Kentucky: www2.ca.uky.edu/agcomm/pubs/ho/ho15/ho15.pdf. 

While erect types are the easiest to maintain, flavor and sweetness can be subjective and growers will benefit from experimentation with an assortment of varieties. At the UT Gardens, Knoxville, Kitchen Garden a trailing variety called ‘Triple Crown’ has been the crowd favorite for more than five years due to heavy production of sweet, flavorful berries. The University of Arkansas is a leader in breeding blackberries, developing cultivars that have improved flavor, production, disease resistance, and minimized maintenance. Of course, thornlessness has been addressed and several varieties are available as well as a relatively new group of blackberries that will produce on the first year canes, which revolutionizes commercial blackberry production. Recommended University of Arkansas cultivars that produce on floricanes (second year) are named for Native American Indian tribes, and those that will produce on the primocanes will have the prefix ‘Prime” attached to the name. The University of Arkansas resources are included here as a starting point: www.uaex.edu/yard-garden/fruits-nuts/berries.aspx.

Recommended University of Arkansas blackberry cultivars for home gardens include:

• Thorny: Chickasaw, Choctaw, Kiowa and Shawnee
• Thornless: Apache, Arapaho, Natchez, Navaho, Osage and Ouachita

Additional information about blackberry production can be found online at the UT Extension publications page: extension.tennessee.edu/publications. Just enter “blackberries” into the search engine.

The UT Gardens includes plant collections located in Knoxville, Jackson and Crossville. Designated as the official botanical garden for the State of Tennessee, the collections are part of the University of Tennessee Institute of Agriculture. The Gardens’ mission is to foster appreciation, education and stewardship of plants through garden displays, educational programs and research trials. The Gardens are open during all seasons and free to the public. For more information, see the Gardens website: ag.tennessee.edu/utg.

Contacts: 

Holly Jones, UT Gardens, Knoxville

Carol Reese, UT Extension Horticulture Specialist, Western Region