Prime-Jim and Prime-Jan are hybrid blackberry varieties developed by the University of Arkansas. They thrive in sunny locations and grow well in most areas of the country once all possibility of local frost has passed. One of the major differences between Prime-Jim and Prime-Jan and other varieties of blackberries is that Prime-Jim and Prime-Jan produce berries on first-year growth (primicanes) as opposed to producing berries on second-year growth (floricanes) as most other blackberries do. This can make for faster fruiting on new plants.
Choose a sunny location and prepare the soil by rototilling it to a depth of 6 inches or by turning the soil with your spade. Use plenty of organic fertilizer on the soil and work it into the garden dirt with your spade or rototiller. Don't plant until all possibility of local frost has passed.
Keep the roots of your Prime-Jim and Prime-Jan blackberries damp until planting. Dig a hole twice as large as necessary to accommodate the roots of your plants and carefully pack soil around the plant to the same depth that the plant was grown at the nursery. Set plants at least 24 inches apart.
Mulch around plants to retard the growth of weeds and to help keep the soil damp but not soggy.
Trim your primicanes (first year growth) to 3 feet once they start to grow. This will keep the height of the plant down and will also encourage the production of fruit. Wear gloves when trimming your plants as the thorns can hurt.
Harvest your blackberries at the end of the summer growing season.
Use your garden shears to remove all dead growth. Cut all primicanes to within 3 inches of the base of the plant once all berries have been harvested.