(Rubus spp.)

family Rosaceae

Fall fruiting blackberry
Fall fruiting blackberry

Cultivars tested

‘Illini Hardy’, ‘Fort Kent King’, ‘Chester’, ‘Doyle’s’, ‘Prime Jim’, ‘Prime Jan’, ‘Triple Crown’, ‘Native’

Description and site preference

Type and size – bramble cane fruit of various heights and lengths
Hardiness zone – 4-9
Exposure – full sun to part shade
Soil – loam with good organic matter
Drainage – well-drained

Economic factors

Years to harvest – 2 years to significant harvest (some after 1 year)
Maintenance – medium to high
Life of planting – 20+ years
Machine harvest potential – intermediate
Suitable markets – fresh and processed

Native blackberry prior to pruning
‘Native’ blackberry prior to pruning

Notable features

Nutritional highlights – nutritionally balanced, high in salicylic and ellagic acids (see Wikipedia reference, below.)
Adaptability – good at most well-drained sites
Pest issues – moderate to high (reduced with good pruning management)
Invasive potential – native but can spread and become a nuisance
Environmental benefits – attracts native pollinators

Integration characteristics

Shared management – intermediate
Shared equipment – intermediate
Shared processing – high
Co-marketing – intermediate to high

Integration potential – very good

Adapted cultivars could be grown successfully in an integrated system. Superior native clones could be considered.

Native blackberry fruit
‘Native’ blackberry with ripening fruit

History and background

Blackberry is a well-known fruit that is overlooked and under-used as a commercial crop in northern temperate regions. It is a widely adapted group of more than 375 species, many of which are closely related apomictic micro-species native throughout the temperate northern hemisphere and South America. Blackberry tolerates poor soils, colonizing wasteland, ditches and vacant lots. Some species are naturalized and can become invasive and a serious weed problem.

Evidence suggests that humans have eaten blackberries for thousands of years. Blackberry is eaten fresh and has many familiar uses as a processed fruit today. They contain a compound called salicylic acid that has similar properties to aspirin. It has been proven to numb bodily pains, treat high body temperatures and aid in protecting the body against heart disease. Blackberry also contains high levels of ellagic acid, which has proven reliable for slowing the growth of particular cancer cells in animal studies (American Cancer Society).

Blackberry is notable for high contents of dietary fiber (both soluble and insoluble), vitamins C, K, folic acid (a B vitamin) and the essential mineral manganese. Blackberry is also high in anthocyanins. Their dark color ranks them among the top-rated fruit for oxygen radical absorbance capacity (ORAC). The seeds contain some oil rich in beneficial Omega 3 and 6 fatty acids, along with protein.(See references to Wikipedia and USDA, below)

High tunnel in April
High tunnel in April with canes mowed off

Available options for northern growers

Despite the prevalence of native blackberry in the northern temperate zone, there is only one commercial selection for that area. Blackberry breeding has been concentrated in the south and far west, where selection for winter hardiness has not been a priority.

‘Illini Hardy’ was developed and patented by the University of Illinois. This is an erect and vigorous selection that is supposed to provide abundant crops of top quality fruit. This selection was planted at Carandale in 2004 as the standard by which other selections could be compared. They transplanted native selections taken from two locations on the farm. Carandale planted another winter-hardy selection offered by Fedco Trees. ‘Fort Kent King’ is probably a superior native selection from that area and appears to be winter-hardy, perhaps to Zone 3. Carandale also added less hardy, thornless varieties for comparison.

High tunnel in late October
High tunnel in late October with some 8-foot-tall primocanes

Another approach to growing blackberries commercially in northern areas is to use primocane varieties for a fall crop, thus bypassing the over-wintering issue. Carandale is experimenting with the original fall fruiting selections introduced by the University of Arkansas. This approach will probably not be practical until earlier fall fruiting varieties are selected. ‘Prime Jim’ and ‘Prime Jan’ set fruit too late in northern areas for the quantity and quality of fruit required for commercial production. Until earlier fruiting selections are found, growers can use season extension – Carandale is experimenting with this option through use of high tunnels.

Observations at Carandale Farm

Floricane production

Carandale purchased ‘Illini Hardy’ plants from Nourse Farms  in 2004. These virus-free tissue cultured plants grew vigorously, producing some fruit in 2005. Production increased for several years as cane density increased by root suckering. The fruit had impressive size compared to native clones in the test plot, but flavor and large seeds were unappealing. They are much more thorny (or prickly) than native clones. Thorns are large and sharp — even the leaves have thorns. Fruit started ripening a little later than the native species and continued for a longer period. Within a few years, the canes started to show symptoms of anthracnose, resulting in much overwintering cane dieback and dried fruit prior to ripening. Some primocanes had crinkled foliage, indicative of a virus. These are removed periodically to prevent spread by insects, if indeed it is a virus.

Native clones, by contrast, have smaller, sweeter, more flavorful fruit. Thorns are smaller and more widely spaced. Genetic variability exists between the two selection sites. One group has fewer but larger canes and virtually no sign of anthracnose disease. The other group root-suckers more freely, and fruit occasionally dries out before maturity, indicative of anthracnose. This clone also has some unequal ripening tendencies where single fruits ripen unevenly (not all druplets ripen simultaneously). Both clones are productive in a commercial setting with most fruit ripening in a 2 to 2 ½ week period.

‘Fort Kent King’, the selection from Maine, has smaller, but very tasty, fruit. The canes are shorter (4-5 feet), but this may be due to the site, which is the only area in the test plot with sandy soil. These plants, added to the test plot in 2006, have spread by root suckering more than other native selections, but this may be due to a difference in soils – clay-based to sand-based. They are not as productive, but the canes over-winter well and have not shown signs of anthracnose.

Carandale purchased the thornless variety ‘Chester’ from Hidden Springs Nursery and added it to the test plot in 2007. ]This semi-erect cultivar is considered hardiest of the thorn-free blackberries, but canes winter-kill most years. They do not root-sucker but spread when cane tips make contact with the soil and take root. Canes overwintered in 2012 and produced a nice crop of fruit with fruit similar size, but better quality and flavor than ‘Illini Hardy’.

Carandale obtained three plants of ‘Doyle’s’ thornless selection in 2008. They fruited in 2012. Fruit and plant size was smaller than ‘Chester’ but similar in growth habit and fruit quality. Neither thornless variety has shown significant anthracnose symptoms, but they are not winter-hardy enough for reliable production in the test area.

In 2008, Carandale planted another thorn-free selection from Miller Nurseries. ‘Triple Crown’ is less winter-hardy than ‘Chester’ and ‘Doyle’s’. Carandale never harvested enough fruit to make a fair evaluation of flavor and quality. Thorn-free cultivars are not reliably winter-hardy, but Carandale’s intention was to experiment with mitigation techniques like laying the canes down and covering them with straw for winter protection.

Primocane production

In 2006, Carandale purchased ‘Prime Jim’ and ‘Prime Jan’ from Indiana Berry and Plant Co. These were the first selections released for fall fruiting. They were observed in an open field through 2010. Both selections are erect and thorny (although without thorns on the leaves like ‘Illini Hardy’). Bloom and fruit set were so late in the summer that most of the crop froze before ripening. The fruit was large and attractive, but quite tart. Tartness could be indigenous to the cultivars or, if it is poor sugar conversion, seasonally induced by low fall light and temperatures. Carandale saw little significant difference between the selections, but ‘Prime Jan’ did seem smaller and less productive.

In 2011, Carandale erected a seasonal high tunnel courtesy of the Natural Resources Conservation Service seasonal high tunnel cost-share program (see reference below). The purpose of a high tunnel, which is essentially an unheated greenhouse, is to extend the growing season. In theory, Carandale should be able to extend their growing season by two months — one in the spring and one in the fall. At Carandale, 2012 was a transitional year., Although they saw a substantial increase in plant growth, the majority of canes never initiated bloom. Fruit set on the canes that did initiate bloom was variable, likely due to a pollination issue. Canes that set fruit in this environment had spectacular fruit size and appearance (larger fruit averaged 13 grams). This remains an experiment in progress.


There is untapped potential for making blackberries a profitable commercial fruit crop in the northern temperate zone, at least to Zone 4. Existing selections for commercial production have emphasized other needs. Carandale research suggests there is enough genetic variability in native northern blackberry clones to support a breeding program for selections suitable for northern growers. Under comparable conditions, the native clones have superior yield, fruit quality, disease resistance and less thorniness than the northern commercial standard bearer ‘Illini Hardy’. Fruit is smaller, but flavor is better. The seeds are smaller and less objectionable. Blackberries bloom late enough to avoid late-spring freeze damage.

Primocane fruiting blackberries will probably not be a commercially viable option for northern growers for the foreseeable future. More breeding work needs to be done to develop selections that initiate primocane fruit buds reliably and early enough for northern growers. There may be niche opportunities with controlled environmental growing systems, such as high tunnels


Wikipedia entry on Blackberry
The Berry Grower’s Companion, by Barbara L. Bowling
EQIP Seasonal High Tunnel Initiative
USDA Nutrient Data Library: Blackberries
American Cancer Society: Ellagic Acid

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