Black-Eyed Susan

By Deborah Light-Pacheco  UCCE Master Gardener

Common name of plant: Black-eyed Susan Vine

Scientific name: Thunbergia (T.alata, T.erecta, T.grandiflora, T.gregorii, T.mysorensis

Planting area: Zones vary by species, Sunset zones 16-24, H1, H2

Size: vines 10-20 feet long with flowers of 1 inch and leaves up to 3 inches; varies by species

Bloom Season: All summer

Exposure: Full sun to partial shade in hottest climates

Pruning needs: deadheading and general size control

Water needs: Regular

Snapshot:  Black-eyed Susan vines are native to Africa, Madagascar and Southern Asia. They are easy to grow climbers for trellises or on slopes as a ground cover.  This plant can grow as a perennial in mild climates or can be treated as an annual. The stems may trail 8-10 feet in a single season and if left undeterred and in a frost-free area, vines can stretch to 20 feet. The Sunset Western Book states that vines in Hawaii are known to grow up to 50 feet in length!  Black-eyed Susan vine leaves are triangular and flower nonstop in gorgeous shades of canary yellow, copper, terra cotta and mixed shades of rose, ivory, salmon and apricot—all with a dark eye at the center. 

These vines twine around anything they can and so must be planted with care to avoid strangling other valued plants such as roses, shrubs and trees.  Black-eyed Susan vines will grow in a pot or in hanging baskets.  They love full sun to part shade and must have shade in the afternoon during summer's most intense heat.  Rich moist soil that drains well will provide the vines with needed nutrients.  Weekly watering for in-ground plants and for those in pots or baskets, especially in the heat, will make for a happy, healthy plant. In the fall, deadhead and remove any infected leaves and cut back as needed after bloom. Seeds can be collected and stored for next season.

Black-eyed Susan vines can be started inside or outside from seeds and require 21 days or more to germinate.  Starting indoors requires seed pots and seed-starting mix.  Keep seeds consistently warm and moist.  Once nighttime temperatures are above 50 degrees Fahrenheit, seedlings may be transplanted into a sunny spot with well drained, moist soil. 

Black-eyed Susan Vines are a gorgeous and easy way to add color to your garden.  They are a good source of nectar for pollinators and rarely develop pest or disease issues.  If a plant does pick up whiteflies or spider mites, insecticidal sprays should fix the issue.  Have fun with this plant!  You will be greatly rewarded with tons of sunny flowers and lush vines.

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