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 in the rose family, grown for large, soft berries that ripen a deep reddish-purple. It came out of a tangled cross of blackberry, raspberry, loganberry, and dewberry, and Knott's Berry Farm in California turned it into a household name. The fruit is sweeter and more aromatic than a straight blackberry, with a flavor all its own.
Like other trailing brambles, it grows on a two-year cane cycle. The first-year canes, called primocanes, just put on growth. The next summer those same canes flower and fruit as floricanes, then die back, so every year brings a mix of old wood to remove and new wood to tie in. That rhythm shapes how you prune and trellis the plant.
It is a vigorous grower and a willing spreader, throwing roots wherever a cane tip touches soil. Give it full sun, deep rich ground, and a strong support, and it crops well for years. Leave it untrained and it sprawls into a thorny thicket, so a trellis is not 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 onto a trellis, cut out the spent fruiting canes after harvest, and tie in the new ones for next year.
Light
Boysenberries crop best in full sun, which means six or more hours a day. They tolerate a little afternoon shade, but light fruiting and weaker canes are the price, and a shaded, damp plant is far more prone to disease.
Water
Give the plants 1 to 2 inches of water a week, and lean toward the higher end while the fruit is setting and ripening. Drip irrigation is the way to do it, since wetting the leaves and berries invites rot. Steady moisture through summer makes for fuller, juicier fruit.
Soil
Plant in deep, well-drained sandy loam with plenty of organic matter worked in. A slightly acidic pH of 5.8 to 6.5 suits them, and the deep, rich ground gives the wide-ranging roots room to run.
Temperature
The plants handle a broad range, from about 41°F to 86°F (5°C to 30°C) through the growing season, and they are hardy in zones 6 to 9. Long stretches of extreme heat can stress the fruit, so a little afternoon shade helps where summers run hot.
Humidity
Average humidity in the 40% to 70% range is fine for boysenberries. What matters far more is airflow, because still, damp air around crowded canes is exactly what gray mold and cane diseases want.
Feeding
Feed once in early spring as growth resumes, using a balanced complete fertilizer such as 10-10-10 or a top-dressing of aged compost. A split nitrogen application over the season works too. Go easy, since too much feed pushes soft, disease-prone growth.
Pruning
Pruning is the heart of growing this plant. After harvest, cut the spent fruiting floricanes right to the ground, then train and tie the fresh primocanes onto the trellis for next year's crop. Thin out crowded canes so air can move and disease stays down.
Repotting
Boysenberries are grown in the ground or in a large trellised bed, not in pots, so there is no repotting to worry about. If you do trial one in a container, watch for roots circling out the bottom and weak, stunted new canes as signs it has run out of room.
Size & spacing
A plant reaches 3 to 6 feet (90 to 180 cm) tall on its trellis, but the trailing canes spread 6 to 10 feet (1.8 to 3 m) wide. Give each plant that much room along the support so the canes can be trained out and air can move between them.
When to plant
Boysenberries follow the seasons of a trailing bramble. Set new plants out in early spring once hard frost has passed, watch for bloom in late spring, and pick the fruit through early to mid summer, roughly June into July across 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 shows up on the canes or the ripening fruit, and damp, crowded plantings are usually behind it. Learn the early signs and you can cut out a problem before it spreads down the row. Match what you see below, then act while it still helps.
Canes that yellow, wilt, and collapse on one side
Verticillium wilt is a soil fungus that clogs the plant from the inside, and there is no cure once it sets in. Cut a wilting cane and you'll often see brown streaking in the wood. Pull and destroy affected plants, and never replant brambles where tomatoes, peppers, or potatoes recently grew, since they leave the same fungus behind.
Fix:
- Remove and destroy affected plants
- Do not replant brambles in the same infested soil
- Choose new sites with no recent solanaceous crops
Gray-centered spots with purple edges on the canes
This is anthracnose, a fungus that takes hold in long wet spells and shows up as sunken lesions that can crack the cane. Cut out and destroy the infected canes, then thin the rest so air moves freely through the planting. A dormant lime sulfur or a labeled fungicide helps where it keeps coming back.
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
Soft berries going fuzzy and gray as they ripen
Gray mold settles on ripening fruit during cool, damp weather, especially deep inside a crowded canopy. Pick off the spoiled berries the moment you see them and harvest ripe fruit often so it never sits. Keeping the foliage dry and the canes well spaced is what stops it spreading.
Fix:
- Pick and remove infected fruit promptly
- Harvest frequently when ripe
- Improve airflow and reduce canopy density
Toxicity
Good news for a household with pets: the boysenberry is not poisonous. The leaves and fruit are safe for cats, dogs, and other animals, and the ripe berries are good for people too. The one real hazard is physical, not chemical, since thorny canes carry sharp prickles that can scratch, so wear gloves and pick a thornless type if pets share the garden.
Safe for
People · Cats · Dogs · Horses · Rabbits · Livestock · Birds
Cats Safe
No poisoning risk here. A cat that nibbles a leaf or a berry is fine, though the thorns on a thorny cane can scratch.
Dogs Safe
The plant won't harm a dog, and a few ripe berries make a safe treat. A big helping of fruit can loosen the stomach, so keep it modest.
Horses Safe
Horses can graze the foliage and fruit without trouble. Watch only for the prickles on thorny canes.
Rabbits Safe
Rabbits can eat the leaves and the fruit safely. Offer berries in small amounts, since too much sugary fruit upsets a rabbit's gut.
Livestock Safe
Cattle, goats, and sheep browse bramble foliage with no ill effect, and goats happily clear a thicket.
Birds Safe
Birds love the ripe berries and come to no harm. Netting is more about saving your crop than protecting them.
People Safe
The ripe berries are a sweet, edible fruit eaten fresh or cooked. The only real hazard is the thorns, so wear gloves when 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 come down to one real choice: whether you want thorns or not. Both bear the same big, dark fruit.
Thornless Boysenberry
A smooth-caned selection that carries the same large, dark wine-red berries without the prickles, which makes picking and training the canes far easier.
Original (thorny) Boysenberry
The classic Rudolph Boysen selection that Knott's Berry Farm made famous, with vigorous thorny trailing canes and large, 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 easy to multiply from the plant you already have, since the long trailing canes root 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 easy way in. In late summer or early fall, bend a trailing primocane down and bury its growing tip a few inches deep. Roots form over the next several weeks, and by the following spring you can cut the new plant free and move it where you want it.
Stem cuttingsModerate
Late winter dormant season or early summer for softwood · Several weeks to a few months
You can also root cuttings, either dormant cane sections taken in late winter or softwood cuttings in early summer. Keep them moist and they take anywhere from several weeks to a few months to root. For trailing types like this one, tip layering is the easier and more reliable bet.
Myths
A boysenberry is just another name for a blackberry.
It traces back to a tangled cross of blackberry, raspberry, loganberry, and dewberry, so it carries genes from all four. The result is its own fruit, large and soft with a dark reddish-purple color and a flavor no straight blackberry quite matches.
Boysenberries fruit on brand-new canes in their first year.
Like most trailing brambles, they grow on a two-year cycle. A cane spends its first season just growing, then fruits the following summer as a floricane before it dies back, which is why you cut out the spent canes and tie in the fresh ones each year.