Prime-Ark 45 Blackberry
Rubus subgenus Rubus 'Prime-Ark 45'
The first truly successful primocane-fruiting blackberry that produces large, firm berries on both first and second-year canes for extended harvests. This thornless variety delivers exceptional fruit quality with sweet, flavorful berries that rival the best traditional blackberries. The compact, manageable growth habit makes it perfect for home gardens where space is at a premium.
Harvest
60-70d
Days to harvest
Sun
Full sun
Zones
6–9
USDA hardiness
Difficulty
Moderate
Planting Timeline
Showing dates for Prime-Ark 45 Blackberry in USDA Zone 7
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Prime-Ark 45 Blackberry · Zones 6–9
Growing Details
Zone-by-Zone Planting Calendar
Complete Growing Guide
Prime-Ark 45's primocane-fruiting habit means you'll harvest from both summer and fall flushes, requiring staggered pruning: remove only spent canes after fall harvest, leaving first-year canes to fruit again in spring. Plant in full sun with well-draining soil to prevent root rot, which this cultivar is moderately susceptible to in wet conditions. Unlike traditional blackberries, Prime-Ark 45 won't require aggressive thorniness management, but its compact growth can mask pest problems—monitor closely for spider mites and Japanese beetles, which readily colonize dense canopies. Water consistently during fruit development to prevent the berry cracking that occasionally occurs during heavy rain cycles. One essential tip: install support trellising early, as the thornless canes lack natural climbing defense and sprawl horizontally without structure, reducing air circulation and creating disease pressure in humid climates.
Light: Full sun (6 or more hours of direct sunlight a day). Soil: Clay, High Organic Matter, Loam (Silt), Sand. Soil pH: Acid (<6.0). Drainage: Good Drainage, Moist, Occasionally Dry. Growth rate: Rapid. Maintenance: Medium. Regions: Coastal, Mountains, Piedmont.
Harvesting
Prime-Ark 45 blackberries reach peak harvest readiness when they achieve a deep, glossy black color and feel slightly soft to gentle finger pressure, indicating maximum sugar development. Unlike traditional blackberries, this primocane-fruiting variety enables continuous harvesting throughout the season by producing fruit on both first and second-year canes, extending your picking window considerably. For optimal flavor and firmness, harvest berries in early morning after dew dries, as cooler temperatures help maintain the berry's structure during collection. Check plants every two to three days during peak season, prioritizing fully darkened berries while leaving any that retain purple or red tones for additional ripening.
Fruits vary in size and color with many maturing to black or red. Usually edible but vary in taste and sugar content. They also vary as to when they are available.
Type: Aggregate, Drupe.
Garden value: Edible
Storage & Preservation
Fresh Prime-Ark 45 blackberries keep best when stored unwashed in shallow containers in the refrigerator at 32-35°F with high humidity. They maintain quality for 5-7 days when properly stored, longer than most primocane varieties due to their exceptional firmness. Line containers with paper towels to absorb excess moisture and prevent mold.
For freezing, rinse berries gently and pat dry, then freeze on baking sheets before transferring to freezer bags — this prevents clumping. Prime-Ark 45's firm texture makes it excellent for cobblers and pies even after freezing. The berries also make superior jam due to their balanced sweet-tart flavor and natural pectin content. Dehydrate at 135°F for 8-12 hours for chewy dried berries that retain more flavor than most varieties due to their concentrated sweetness.
History & Origin
Prime-Ark 45 was developed by Dr. John Clark at the University of Arkansas and released in 2009 as part of their groundbreaking primocane-fruiting blackberry breeding program. This variety represents a major breakthrough in blackberry genetics — it was the first commercially viable primocane-fruiting blackberry that could reliably produce two crops per year while maintaining fruit quality comparable to traditional floricane varieties.
The University of Arkansas has been the world leader in blackberry breeding since the 1960s, developing over 40 varieties including most thornless types. Prime-Ark 45 was selected from thousands of seedlings for its combination of primocane-fruiting ability, thornless canes, large berry size, and excellent flavor. The 'Prime-Ark' name reflects Arkansas's leadership in primocane breeding, while '45' refers to its selection number in the breeding program.
This variety solved a major challenge that had frustrated breeders for decades — previous primocane blackberries produced small, seedy berries with poor flavor. Prime-Ark 45 changed the industry by proving that primocane varieties could match traditional blackberries in all quality measures while extending the harvest season.
Advantages
- +Produces fruit on both primocanes and floricanes for extended harvests
- +Thornless canes eliminate injuries during pruning and harvesting
- +Compact growth habit fits well in small home garden spaces
- +Large, firm berries with excellent sweet flavor and mild tartness
- +First truly successful primocane-fruiting blackberry variety on market
Considerations
- -Susceptible to spotted wing drosophila and requires vigilant pest monitoring
- -Vulnerable to cane blight and crown gall diseases requiring prevention
- -Moderate difficulty level means it needs proper training and care
Companion Plants
Comfrey is doing the most physical work here — its roots go down 6 feet or more, pulling up calcium and potassium from below the blackberry root zone, and chopped leaves laid as mulch return that nutrition to the surface without any bag of fertilizer. In our zone 7 Georgia garden, aphid pressure on new canes can show up by late April, so chives and garlic earn a spot at the row ends; the sulfur compounds they release make new shoot tips a less attractive landing pad. Clover in the row middles fixes atmospheric nitrogen without pushing the kind of excessive vegetative growth that comes with synthetic N and crowds out your fruiting wood. Keep black walnut at least 50 feet away — juglone, the allelochemical it releases through roots and decomposing hulls, is genuinely toxic to Rubus and will decline a planting slowly enough that you might not connect the cause for a season or two.
Plant Together
Chives
Repels aphids and Japanese beetles while improving soil with sulfur compounds
Marigold
Deters nematodes and aphids through natural pest-repelling compounds
Garlic
Repels aphids, spider mites, and fungal diseases with strong aromatic oils
Comfrey
Deep roots bring nutrients to surface, leaves make excellent mulch and fertilizer
Nasturtium
Acts as trap crop for aphids and cucumber beetles, attracts beneficial insects
Clover
Fixes nitrogen in soil and provides ground cover to suppress weeds
Yarrow
Attracts beneficial insects and improves soil health with deep taproot
Tansy
Repels ants, mice, and flying insects while attracting beneficial predators
Keep Apart
Black Walnut
Produces juglone toxin that inhibits growth and can kill blackberry plants
Raspberries
Share common diseases like anthracnose and verticillium wilt, increasing infection risk
Pine Trees
Acidify soil excessively and compete for nutrients, creating poor growing conditions
Nutrition Facts
Per 100g serving. % Daily Value based on 2,000 calorie diet. Source: USDA FoodData Central (FDC #173946)
Pests & Disease Resistance
Resistance
Good resistance to orange rust and anthracnose
Common Pests
Spotted wing drosophila, aphids, thrips, birds
Diseases
Cane blight, crown gall, rosette disease
Troubleshooting Prime-Ark 45 Blackberry
What you'll see, why it happens, and what to do about it.
Small, soft berries with larvae inside, fruit fermenting or collapsing before fully ripe — typically showing up on the fall crop
Likely Causes
- Spotted wing drosophila (Drosophila suzukii) — a vinegar fly that lays eggs inside ripening fruit before it's even picked, unlike common fruit flies that only hit rotting fruit
- Delayed harvest leaving ripe fruit on the cane too long
What to Do
- 1.Pick every 2-3 days once fruit starts coloring — don't let ripe berries sit on the cane
- 2.Set out apple cider vinegar traps with a drop of dish soap around the patch to monitor and reduce adult populations
- 3.After harvest, pull any dropped or overripe fruit off the ground immediately — it's a breeding site
Canes wilting and dying back mid-season, with dark brown or purplish lesions visible at or near the soil line
Likely Causes
- Cane blight (Leptosphaeria coniothyrium) — a fungal pathogen that enters through pruning wounds or natural cracks in the bark
- Overcrowded canes with poor airflow, or leaving old cane stubs after pruning
What to Do
- 1.Cut out affected canes 6 inches below the visible lesion and put them in the trash — not the compost pile
- 2.Disinfect pruning shears with 70% isopropyl alcohol between cuts so you're not dragging the pathogen from cane to cane
- 3.Thin to no more than 4-6 canes per plant to open up airflow; this fungus thrives where humidity sits
New shoot tips stunted and distorted, young leaves curled or sticky, small green or black insects visible on the growth
Likely Causes
- Aphid colonies (commonly Amphorophora agathonica or related species) feeding on tender shoot tissue
- Loss of natural predators — ladybugs and parasitic wasps disappear fast if broad-spectrum insecticides have been used anywhere nearby
What to Do
- 1.Hit the colonies with a firm jet of water from the hose — it dislodges more than you'd expect and leaves beneficials alone
- 2.For a heavy infestation, apply insecticidal soap at 2-4 tablespoons per gallon, targeting leaf undersides where aphids cluster
- 3.Chives or garlic planted at the row ends help deter future pressure through sulfur compounds — both are already pulling weight as companions
Frequently Asked Questions
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Sources & References
External authority sources used in compiling this guide.
See the Methodology page for how this data is sourced, what's AI-assisted, and known limitations.