Shrub · Rosaceae
Boysenberry
Rubus ursinus × idaeus
Give it full sun, a sturdy trellis, and a yearly prune, and the boysenberry crops with big, wine-dark fruit.
Full sun
Every 5–7 days
41–86°F · 5–30°C
USDA 6–9
Overview
The boysenberry is a trailing bramble of the rose family, prized for big, soft berries that deepen to a dark reddish-purple as they ripen. Its parentage is a knot of blackberry, raspberry, loganberry, and dewberry, and Knott's Berry Farm in California carried the name into every kitchen. The fruit runs sweeter and more aromatic than a plain blackberry, with a character entirely its own.
Like the other trailing brambles, it lives on a two-year cane cycle. The first-year canes, the primocanes, do nothing but lengthen and thicken. The following summer those same canes flower and set fruit as floricanes, then die away, so each year leaves you a mix of old wood to clear and new wood to tie in. That cadence dictates how you cut and trellis the plant.
It grows fast and spreads with a will, rooting down anywhere a cane tip brushes the soil. Set it in full sun, deep rich ground, and against a strong support, and it bears well for years. Leave the canes loose and they sprawl into a thorny, tangled thicket, which is why a trellis is never optional.
Care
The short version: full sun, deep well-drained soil rich in organic matter, and 1 to 2 inches of water a week. Train the canes up a trellis, cut the spent fruiting canes to the ground after harvest, and tie in the fresh ones for next year.
Light
Boysenberries fruit best in full sun, six hours a day or more falling on the canes. They will take a touch of afternoon shade, but you pay for it in lighter fruiting and thinner, weaker canes, and a shaded, damp plant runs a far greater risk of disease.
Water
Lay on 1 to 2 inches of water a week, leaning toward the top of that range while the berries are setting and swelling. Drip irrigation is the right way to deliver it, since water sitting on leaves and fruit invites rot. Steady summer moisture is what plumps the berries fuller and juicier.
Soil
Plant into deep, well-drained sandy loam turned through with plenty of organic matter. A slightly acidic pH of 5.8 to 6.5 suits them, and that deep, rich ground gives the far-reaching roots the room they want.
Temperature
The plants take a wide swing, holding up from about 41°F to 86°F (5°C to 30°C) across the growing season, and they prove hardy through zones 6 to 9. Long runs of extreme heat can stress the fruit, so a little afternoon shade earns its keep where summers turn fierce.
Humidity
Average humidity in the 40% to 70% band suits boysenberries fine. What counts for far more is airflow, because still, damp air pooling around crowded canes is precisely the setting gray mold and cane diseases look for.
Feeding
Feed once in early spring as the canes break growth, with a balanced complete fertilizer such as 10-10-10 or a top-dressing of aged compost. A split nitrogen feed across the season works as well. Hold back, since an overfed plant pushes soft, sappy growth that disease finds easy.
Pruning
Pruning sits at the center of this plant. Once harvest ends, cut the spent fruiting floricanes flush to the ground, then guide and tie the fresh primocanes onto the trellis for next year's crop. Thin away any crowded canes so air moves through and disease finds no foothold.
Repotting
Boysenberries grow in open ground or a large trellised bed, not in pots, so there is no repotting to think about. Should you trial one in a container anyway, look for roots circling out the drainage holes and weak, stunted new canes as the signs it has outgrown the space.
Size & spacing
A plant stands 3 to 6 feet (90 to 180 cm) tall once trained up its trellis, while the trailing canes reach 6 to 10 feet (1.8 to 3 m) out to the sides. Allow each plant that full stretch along the support so the canes can be fanned out and air can pass between them.
When to plant
Boysenberries move with the seasons of a trailing bramble. Get new plants in the ground in early spring once hard frost is behind you, look for bloom in late spring, and gather the fruit across early to mid summer, roughly June into July through most of zones 6 to 9.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: early spring after danger of hard frost has passed
- Harvest: blooms late spring; harvest early to mid summer (roughly June to July)
Hardiness
USDA hardiness zones: 6–9
Temperature: down to -23°C
Troubleshooting
Most boysenberry trouble surfaces on the canes or the ripening fruit, and damp, crowded plantings nearly always sit behind it. Learn to read the first marks and you can cut a problem out before it travels down the row. Match what you find below, then act while acting still does some good.
Yellowing canes that wilt and fold on one side
Watch for whole canes going limp and yellow on a single flank of the plant, the telltale shape of Verticillium wilt, a soil fungus that plugs the water channels from the inside with no cure once it arrives. Slice a wilting cane crosswise and brown streaks run through the pale wood. Dig up the affected plants and destroy them, and never set brambles where tomatoes, peppers, or potatoes recently stood, since they leave the same fungus in the ground.
Fix:
- Remove and destroy affected plants
- Do not replant brambles in the same infested soil
- Choose new sites with no recent solanaceous crops
Sunken gray lesions ringed in purple along the canes
Run a finger along an affected cane and you can feel the anthracnose lesions, sunken pits with gray centers and purple rims that crack open as they widen, with small matching spots dotting the leaves. The fungus moves in during long wet spells. Cut out the marked canes and burn them, thin the rest so air slips through, and reach for a dormant lime sulfur or labeled fungicide where it keeps returning.
Fix:
- Prune and remove infected canes and destroy them
- Improve air circulation by thinning canes and weeding
- Apply a labeled fungicide or dormant lime sulfur per extension guidance
Ripening berries turning soft, watery, and fuzzy gray
When gray mold takes a berry, the fruit goes soft and watery and a fine gray fuzz spreads over its dark skin, worst on the fruit buried deep in a crowded canopy during cool, damp weather. Pull off every spoiled berry the moment it shows and pick the ripe fruit often so none sits long enough to rot. Keeping the leaves dry and the canes spaced wide is what halts the spread.
Fix:
- Pick and remove infected fruit promptly
- Harvest frequently when ripe
- Improve airflow and reduce canopy density
Toxicity
Easy news for a home with pets: the boysenberry is not poisonous. Its leaves and fruit are safe for cats, dogs, and other animals, and the ripe berries feed people just as well. The single real hazard is physical, not chemical, since thorny canes carry sharp, hooked prickles that can scratch, so wear gloves and choose a thornless type if pets roam the garden.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats Safe
There is no poisoning to fear. A cat that bites a leaf or a soft berry comes to no harm, though the curved prickles on a thorny cane can leave a scratch.
Dogs Safe
Nothing in the plant will harm a dog, and a few of the dark ripe berries make a safe treat. Pile on too much of the soft fruit and you'll loosen the stomach, so keep the handful small.
Horses Safe
Horses can crop the leaves and the fruit with no ill effect. The only thing to mind is the sharp prickles studding a thorny cane.
Rabbits Safe
The leaves and the berries are both safe for rabbits to nibble. Hand over the sweet fruit sparingly, since a heavy dose of sugar upsets a rabbit's gut.
Livestock Safe
Cattle, goats, and sheep browse the bramble foliage without trouble, and goats will strip a thorny thicket bare given the chance.
Birds Safe
Birds flock to the ripe berries and take no harm from them. Drape netting to save the crop for yourself, not to shield the birds.
People Safe
The large soft berries are sweet and edible, good eaten fresh from the cane or cooked down. The thorns are the only real danger, so glove up before you prune.
The main hazard is physical: most boysenberry canes bear sharp recurved thorns/prickles that can scratch pets and people; thornless selections exist and are safer to handle. Wear gloves when pruning or training canes.
Varieties
Boysenberries narrow down to one true decision: thorns or no thorns. Either way the canes hang with the same big, dark fruit.
Thornless Boysenberry
Its canes run long and smooth with no prickles at all, yet they carry the very same large, dark wine-red berries, so your hands stay clear of thorns as you pick and tie.
Original (thorny) Boysenberry
Rudolph Boysen's original selection, the one Knott's Berry Farm made famous, throws vigorous trailing canes bristling with thorns and hangs them with large, deeply aromatic fruit.
Companions
Boysenberries do best away from their disease-sharing neighbors, and a few aromatic plants nearby can help keep pests down.
Plant near
Garlic and onions: Alliums planted nearby can help deter some pests around brambles.
Keep apart
Tomatoes, peppers, potatoes, and eggplant: These solanaceous crops can harbor Verticillium wilt that infects brambles, so avoid planting brambles where they recently grew.
How to propagate
Boysenberries are simple to multiply from a plant you already have, because the long trailing canes strike roots almost anywhere they meet the ground.
LayeringEasy
Late summer to early fall · Roots form over several weeks; transplant the following spring
Tip layering is the simplest route. In late summer or early fall, bow one of the long trailing primocanes down to the ground and bury its growing tip a few inches deep. Roots knit in over the coming weeks, and by the next spring you can sever the rooted young plant and shift it wherever you like.
Stem cuttingsModerate
Late winter dormant season or early summer for softwood · Several weeks to a few months
Cuttings root too, either bare dormant cane sections taken in late winter or soft green softwood shoots cut in early summer. Hold them moist and they strike root anywhere from several weeks to a few months out. For a trailing type like this, though, tip layering stays the easier and surer choice.
Myths
A boysenberry is just another name for a blackberry.
Its parentage is a tangle of blackberry, raspberry, loganberry, and dewberry, all four bloodlines folded into one. The result is its own fruit, large and soft, colored a dark reddish-purple, carrying a flavor no plain blackberry can match.
Boysenberries fruit on brand-new canes in their first year.
Like most trailing brambles, they run on a two-year clock. A cane spends its first season only stretching out and growing, then bears fruit the next summer as a floricane before dying back, which is exactly why you cut away the spent wood and tie in the fresh canes every year.