Growing Blackberries in California
Of all the berries, blackberries are the best set for California, primarily due to their ability to stand our heat. Blackberries grow well in most soils, but prefer deep, well-drained alluvial soils, such as we have in most of Ventura County.
Blackberries require frequent watering so the soil stays uniformly moist. They do very well in coastal areas as the mild temperatures bring out the best tastes and prolong their maximum flavor.
Blackberries come as erect or trailing; erect types will stand up right while trailing types are limp. Most of the blackberries are erect types. Both types require support to do their best and to keep them within bounds.
Berries live for many years, but put out new growth one season (primocanes) and produce fruit on those canes the second season (floricanes). The floricanes die after fruiting and must be removed. The berries are borne on short lateral (side) shoots that grow from the floricanes. For this reason, if you must limit the size of blackberry, cut the tip of the floricane.
Recommended erect types are: Black Satin (mid season), Cherokee (mid season), Cheyenne (early), Chester (late), Darrow, Hull Thornless (mid season to late), and Shawnee (mid season).
Trailing varieties are: Boysen (mid season), Kotata (mid season), Logan (early), Marion (mid season), Ollalie (mid season), Silvan (early to mid season), Tayberry, Waldo (mid season) and Young (mid season).
Blackberries do best in sandy or loamy, well-drained soils with a pH of 5.5 to 6.5. A good supply of organic matter in the soil improves aeration, drainage and moisture retention giving an even moisture level. Add new organic matter (ideally compost) to beds before planting new plants, and top-dress with mulch or compost. It is a good idea to refresh the compost each summer or fall to supply the nutrients the plants will need as they grow the following season.
Raised beds will aid in keeping the soil drained and also make tending the plants each year easier. An ideal height is 8” to 10” high (the plants are shallow rooted).
Planting/Transplanting Blackberry Plants
The best time to plant or transplant is in the fall or winter while the plants are dormant, or as early as you can work the soil in the spring. Dig a shallow hole (remember, the roots are shallow), then spread the roots out to cover the hole. Trim off any damaged roots. The crown of the plant should be replanted at the same height it was before, never lower in the soil (this promotes rot at the soil line). Firm the soil around the roots, water, and then trim the canes to 6”.
Space new plants 2’ to 4’ apart. Planting much closer together starts to crowd the plants where they are competing for sunlight and nutrients, and the total crop will not be as good as possible with more relaxed spacing.
If you use organic fertilizers such as compost or other source (such as well-rotted steer manure), spread it in late fall or early winter, and add 50 pounds per 100’ of row. If you decide on inorganic fertilizers, apply them in the spring (they don’t need to age) when new growth is starting. Apply 5 to 6 pounds of 20-20-20 per 100’ of row.
If your plants are not vigorous by early summer or when bloom is starting, add 1 pound of Urea (Ammonium Nitrate, yes it is a chemical fertilizer, but classed as an organic because of the derivation from cattle urine), and water this in well.
Berry plant requires a fair amount of moisture, but they do not like to be wet as this promotes root rot which can be a serious problem once it s organisms become established in the soil. Generally speaking, twice a week is often enough, and in your rich, loamy soil, less often may be acceptable, especially if you add a 2” layer of course mulch over the bedding area.
Berries require more water when fruiting or during our hot, dry windy periods.
The frequency and duration of water application is an entirely personal matter. The water application rate, type of delivery system, the distance between drippers in a drip system, soil, mulch and exposure all affect your watering schedule. The only way to tell how the moisture level is below the soil line is to look. A moisture probe (available from any home or garden center) works well. A trowel will dip into the soil and show you what it doing, too.
Pruning Plants do not require pruning during their first year.
After the first year, when the new season’s growth (the primocanes) are about 3’ long , tip off the last couple of inches to promotes lateral growth. Alternately, you can leave the tops on (they continue grow longer then) and wrap the tops over the supporting wires or trellis.
Immediately after the harvest, the previous season’s fruit stem (floricanes) need to be removed. Cut the old canes close to the ground, and at the same time, thin the plants to the strongest three or four new primocanes.
Trailing types require a different approach. Lay their new primocanes in a narrow row beneath the plants to prevent injury, When the floricanes are removed, the laid-out new growth can more easily be wound over your frame work.
Weeds are a pest to blackberries, and a layer of mulch over the soil is the best weed prevention. Most weed seed will not germinate under a 2” layer of mulch, and those that do poke up from the mulch layer are easily pulled. If you do need to hoe or dig out weeds, remember that the root system is shallow!
Insects and Mites
Berries are subject to attack by red berry mites that cause abnormal ripening (part of the berry stays red and hard, never ripening). If these are a problem, spray with a mixture of liquid lime sulfur (8 oz. per gallon of water), and wet the 1/2:” to 1” long leaf buds during the spring.
Spider mites cause yellow stippled leaves that eventually turn all yellow, then turn dry and brown. Plant vigor and production is reduced. To treat, prevent mite build up by control dust in the garden, never let the plants get drought-stressed, and (if needed) apply Safer’s ® soap to control the mites.
Raspberry Horntail – This ‘S’-shaped, segmented worm is up to an inch long and has a white body and brown head, spines at the tail, and 3 pairs of legs are near the head. They burrow through the young shoots and cause them to die off starting at the tips. If you cut an affected area open, you will find a tunnel, the dark frass (worm poop) and possibly the worm. Control by removing (and trashing) any affected growth. In extreme cases, a registered insecticide is in order.
Crown borers are worms(larva) up to 1” long, whitish body and brown head. Plants lose vigor, whole branches wilt and die back. The worms may be evident burrowing through the plant tissue if you cut open the base of the affected shoots. Prune out and destroy affected canes, and maintain even water to prevent drought-stress, as the borers are attracted to stressed plant.
Verticillium wilt This fungus builds up in the soil and affects many common garden plants such as tomatoes. There is no cure. Floricanes start by yellowing from the bottom up, wilt and fall over. Dying plants take on a blue-black color, then die during summer as fruiting begins. Small areas may be affected. Remove and destroy any affected plants, and avoid growing again in that area. There are resistant varieties such as Logan, Chehalem and Ollalie berry.
Armillaria root rot is a fungus, survives in the soil for many years, and attacks blackberry canes. Plants weaken rapidly and die off soon after symptoms appear. The disease is indicated by a white fungal growth between the bark and wood near the soil level. Again, there is no cure. Remove and estroy affected plants and do not replant for at least 2 years.
Phytophthora root rot This fungus attacks weakened root systems in excessively wet conditions. Plants fail to leaf out in the spring, then small leaves turn yellow and the entire plant dies. Cut open a plant base or root crown and find rotting material to confirm this disease. Prevent this disease from taking hold by controlling water (do not over water).
Berries affected by yellow rust have yellow. blister-like pustules that start on the Floricanes and spread to the leaves, then canes die out and crack open. Prevention of this disease is simple – avoid overhead watering as the spores are spread by splashing water.
Plants affected by brown rust have orange. blister-like pustules covering the bottom side of a leaf, plants sicken, then seem to recover, but bear no fruit the following year. This disease is spread by wind-borne spores, and there is no cure. Remove and destroy any affected plants, including as much of the root system as possible.