Black Glandular Jewelflower Plant Care

Black Glandular Jewelflower (Streptanthus glandulosus subsp. niger) belongs to the Brassicaceae family within the Streptanthus genus. Black Glandular Jewelflower is native to the Tiburon Peninsula of Northern California, and occurs at elevations below 150 m on serpentine grasslands.

Black Glandular Jewelflower displays an upright, branching growth habit, reaching up to 1.5 ft tall with a spread of approximately 1 ft. Black Glandular Jewelflower produces small, tubular flowers in shades of purple, pink, or white.

Leaf size: approximately 3 inches.

Water a young or newly planted Black Glandular Jewelflower every 7–10 days, soaking the whole root zone, until it is established — usually one to two growing seasons. Established shrubs mainly need water during long dry spells. In a container, water whenever the top few centimetres of soil are dry.

Black Glandular Jewelflower thrives in full sun to partial shade.

Streptanthus glandulosus subsp. niger tolerates temperatures of 50–80°F. Black Glandular Jewelflower prefers humidity levels of 40–60%.

Well-draining sandy loam with added organic matter. Good drainage is essential for Black Glandular Jewelflower to prevent waterlogging, which leads to root rot and fungal issues.

Feed Black Glandular Jewelflower every 6 months during the growing season with a balanced, slow-release fertilizer at the rate on the label. Established shrubs in good soil often need little extra feeding, so let weak growth or pale foliage guide you.

Stop feeding by late summer so new growth can harden before winter.

The PlantoScan app can remind you when to water and when to fertilize each plant.

Choose a spot with full sun to partial shade and well-draining sandy loam with added organic matter. Avoid low spots where water collects after rain.

Black Glandular Jewelflower is suited to USDA Zone 12a.

Plant container-grown or balled-and-burlapped shrubs in spring or early autumn, setting the root flare at soil level, and water well after planting.

Black Glandular Jewelflower can spread to about 1 ft (0.3 m) and reach about 2 ft (0 m) tall. Space plants about 1 ft (0.3 m) apart so mature crowns don't crowd each other, and plant at least half that distance from buildings, fences and paths.

Planning a row or hedge? Try the plant spacing calculator.

Prune Black Glandular Jewelflower while it is dormant in late winter: first remove dead, damaged and crossing branches, then thin lightly for shape.

If it flowers in spring, prune right after flowering instead so you don't remove next year's buds. Never take off more than about a quarter of the shrub in one year.

Black Glandular Jewelflower is frost-tender (hardy to USDA zone 12). In colder areas grow it in a container and move it to a bright, frost-free place before the first frost.

Black Glandular Jewelflower can be propagated through seeds. Similar propagation techniques also apply to streptanthus anceps plant care, which shares the same genus.

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Black Glandular Jewelflower is susceptible to aphids, cabbage worms, flea beetles. Inspect the foliage regularly, especially along leaf undersides and stems. Treat infestations promptly with insecticidal soap or neem oil to prevent spread.

Yellow leaves, brown tips or drooping? See common plant problems and how to fix them.

Black Glandular Jewelflower grows outdoors in USDA Zone 12a. It survives winters down to planting zone 12a. Black Glandular Jewelflower is native to the Tiburon Peninsula of Northern California, and occurs at elevations below 150 m on serpentine grasslands. In cooler regions, grow Black Glandular Jewelflower as a houseplant or bring it indoors before the first frost.