Ribes culverwellii aka Jostaberry

The jostaberry is generally considered an easy-to-grow garden shrub. It tolerates a wide range of soils and pH levels, is largely self-fertile, and has hybrid-vigor disease resistance against several common Ribes problems including American gooseberry mildew, blackcurrant leaf spot, and white pine blister rust. Routine annual pruning and basic mulching are usually sufficient for healthy fruiting.

Jostaberry is a vigorous, multistemmed deciduous shrub reaching roughly 1.8 to 2 meters tall, with a suckering root system that produces new canes from underground runners. Plants display marked hybrid vigor and have large, thornless canes. In garden practice, individual bushes are usually spaced about 3 to 5 feet apart and reach mature size within several years.

Jostaberry prefers consistently moist but well-drained soil. Adequate water is needed especially during fruit development; mulching with a few inches of organic material helps retain soil moisture. The plant is not drought-tolerant and benefits from supplemental watering in dry spells.

Jostaberry adapts to light sandy, medium loamy, and heavy clay soils, but performs best in rich, well-drained, moisture-retentive loam amended with organic matter. It tolerates pH ranging from mildly acidic through neutral to mildly alkaline.

The jostaberry is fully hardy across cool-temperate climates, typically rated USDA zones 5–9 and UK hardiness zone 6, with some sources reporting that selected varieties carry adequate winter hardiness for the Upper Midwest (zones 3–5). Like other Ribes, it does well in northern climates with cool summers.

Apply nitrogen-rich composted material such as well-composted manure — a few shovels per plant — in late fall. Extra nitrogen may be needed if low-nitrogen mulches such as wood chips are used around the base.

Flowering occurs in mid-spring (April through June depending on region), with fruit ripening from July through September. Renew a 2–4 inch organic mulch each year, prune annually in late winter or early spring, and feed in late fall.

Jostaberry produces small, hermaphrodite, self-fertile flowers in clusters during mid-spring, typically April to May. The flowers are insect-pollinated, primarily by bees, and develop into nearly black berries through the summer.

The original and most widely grown cultivar is 'Josta', publicly released in 1977 from a German breeding program that began in 1926 at the Kaiser Wilhelm Institute in Berlin and was completed at the Erwin Baur Institute. Several thornless European selections have been developed, all sharing the complex blackcurrant × gooseberry parentage.

Plant jostaberries outdoors in full sun for best fruiting (partial shade is tolerated but reduces yield), in rich, well-drained soil. Space bushes about 3–5 feet apart, mulch with 2–4 inches of organic matter and renew annually, and prune each winter. The shrub is hardy through USDA zones 5–9 (with some varieties tolerating zones 3–5) and UK zone 6.

Prune annually in late winter or early spring while the plant is dormant. For the first three years, develop 4–5 strong new canes per year, removing only weak or damaged wood. From year four onward, remove the oldest canes annually so the bush carries roughly 9–12 canes of mixed ages, which keeps fruiting wood productive.

Jostaberry is most reliably propagated by cuttings, since the hybrid does not come true from seed. Take half-ripe wood cuttings in July or August, or hardwood cuttings from mature wood between November and February. Seed can be sown if available — fresh seed in autumn, or stored seed after a 3-month cold stratification at 0–5 °C — but the offspring will be variable.

Jostaberry is notably resistant to several diseases that affect its parents, including American gooseberry mildew, blackcurrant leaf spot, white pine blister rust, and big bud gall mite. Powdery mildew is still the most likely problem in humid conditions, so airflow through pruning helps; honey fungus can also damage plants. Possible insect pests include aphids, cane borers, spider mites, fruit worms, and fruit flies, though serious infestations are uncommon.

Flowers are hermaphrodite and self-fertile, so a single bush will set fruit on its own. Pollination is carried out by insects, primarily bees visiting the spring blossoms.

The fruit is highly edible — PFAF rates jostaberry 5/5 for edibility. Berries can be eaten raw or cooked into pies, jams, syrups, and similar preparations. The taste is intermediate between gooseberry (more dominant when under-ripe) and blackcurrant (more dominant when fully ripe), and the fruit is rich in vitamin C, like both parent species.

PFAF assigns Ribes × culverwellii a medicinal rating of 0/5 and lists no specific medicinal uses for the hybrid itself. Related Ribes species, however, have a long ethnobotanical record: Indigenous peoples of North America used species such as R. hudsonianum and R. glandulosum medicinally, and blackcurrant (one parent) has historical use of leaves, bark, and roots as a folk remedy, with seed oil noted for its content of vitamin E and gamma-linolenic acid.

PFAF assigns the hybrid an other-uses rating of 0/5, with no specific non-food uses listed. The parent species do have additional uses: blackcurrant leaves and fruit yield dyes (yellow from leaves, blue/violet from fruit), buds are distilled for perfumery essential oils, seed oil is used in cosmetics, and currants are made into wine and liqueurs such as crème de cassis.

Jostaberry’s native range is A range of garden hybrids.

To ensure optimal growth, the Jostaberry prefers bright indirect light for 6-8 hours each day. Insufficient light can result in slow growth and leaf drop, so it's important to find a well-lit location for this plant. Place it near a window, within a distance of 1 meter (3 feet), to enhance its potential for thriving.

No verified data on the toxicity of this plant exists within Ploi's records. Should you, someone in your family, or your pet ingest plant material with an unknown toxicity level, it is recommended to seek medical advice.