Thunbergia

( thun - BUR - jee - uh )

At-A-Glance Information

This genus of fast-growing tropical annual and perennial vines, commonly called Clockvines, needs partial shade in warmer climates and regular water. They can be damaged by frost but roots will usually stay alive to send up new shoots when the growing season rolls around again in spring; they do well as greenhouse plants. Flowers are showy and bloom in various colors depending on the species. Use these vines to fill in blank areas on walls or fences, in mixed beds and borders, as members of pollinator or wildlife gardens, or simply as specimen plants for their beautiful flowers and foliage.

Thunbergia Species and Varietals

The genus Thunbergia is a member of the plant family Acanthaceae and includes around 150 distinct species. It is named for Swedish naturalist and father of South African botany, Carl Thunberg. The best growing zones for Thunbergia vary depending on the species. For more information, see the descriptions below. To find your zone, click here: Zone Map.

Thunbergia alata (Black-Eyed Susan Vine)
This species is a perennial vine grown in zones 23, 24, and H2, but can be grown as an annual or greenhouse plant anywhere. It has green leaves and summer flowers have black to purple throats. They can be used as a groundcover or as a trellis climbing vine. Varieties include 'African Sunset' (with yellow, salmon, rose, copper or terracotta flowers blushed with red) and 'Lemon Star' (also called 'Sunny Lemon Star', with yellow flowers that bloom over a long season).

Thunbergia atriplicifolia (Natal Primrose)
These plants are native to South Africa and Eswatini, and are perennial shrublets reaching up to about 2 inches tall. It forms a woody base over time, which it resprouts from after cool winter temperatures. Flowers are white and foliage is green.

Thunbergia battiscombei (Blue Glory Vine)
With their large blooms and leafy foliage, these plants are cultivated as herbs as well as ornamental landscape plants. Flowers are purple with yellow throats, and foliage is green. The species is native to tropical areas in Ethiopia, Kenya, Sudan, Uganda, and the DRC.

Thunbergia coccinea (Scarlet Clock Vine)
These plants are perennials with tuberous root systems, and form climbing vines with stems that can reach up to between 10 and 26 feet long. Leaves are lanceolate to ovate and green, and flowers bloom in dangling panicles in January through April in the plant's native range (south and southeast Asia). Flowers are orange-red to pinkish and tubular.

Thunbergia erecta (King's Mantle, Bush Clockvine, Potato Bush)
This vining shrub is best in zones 16, 21-24, H1 and H2 and reaches 6 feet tall and wide. It is native to western Africa. Leaves are dark green and flowers are dark blue with orange or cream-colored throats. Bloom is in summer and fall. Variety 'Alba' has white flowers.

Thunbergia grandiflora (Sky Flower, Bengal Vine, Bengal Trumpet, Blue Skyflower, Blue Thunbergia, Skyvine)
This is a perennial vine that grows well in zones 16, 21-24, H1 and H2 and reaches 20 feet or more. Leaves are a medium to dark green and flowers form in drooping clusters in summer through fall. Blooms are sky blue. Great for covering large structures where shade is needed. Native to China, India, Nepal, Bangladesh, Indochina, and Myanmar.

Thunbergia gregorii (Orange Clockvine, Orange Trumpetvine)
These herbaceous perennials are native to East Africa, and are sometimes cultivated as garden ornamentals. Flowers are bright and pure orange, and vining stems can reach up to between 8 and 10 feet long. It is great at climbing structures, though can also be left to its own devices, where it grows as a groundcover plant. Hardy to 31 degrees Fahrenheit. Flowers bloom year-round in warm climates.

Thunbergia laurifolia (Laurel Clockvine, Blue Trumpet Vine, Akar Tuau, Rang Jeud)
Native to India and Thailand, these vines have heart-shaped green leaves with serrated margins and pale blue to purplish flowers that bloom throughout the year in warm climates. Plants develop tuberous root systems.

Thunbergia mysorensis (Mysore Trumpet Vine, Lady's Slipper Vine)
This perennial vine is best in zones 16, 21-24, H1 and H2 and reaches 15-25 feet with dark green leaves. Flowers are red with yellow interiors and form in long clusters in spring. Can also bloom sporadically throughout the rest of the year. Train this species on a pergola that will allow the dangling clusters to make a spectacular show.

Caring for Thunbergia

Black Eyed Susan vines do well in full sun. On average, they should ideally be receiving between 6 and 8 hours of direct light each day, and will flower and produce the best foliage and fruits the more sun they get. Some afternoon protection from sun is needed in particularly hot areas to avoid over-stressing the plant or causing foliage sunburn. These vines prefer well-draining soil with a pH of between 6.0 and 7.0 (neutral to acidic). If local soils are compacted, do not drain well, or are particularly poor in nutrients, make sure to amend the planting area with plenty of organic matter or compost before installing. Apply a thick layer of mulch around the base of the plant after installation, ensuring that mulch stays at least a few inches away from the stems. This will increase soil moisture retention, suppress weed growth, and maintain a constant soil temperature.

Keep the soil moist while plants establish a strong root system; mature plants are considered somewhat drought-tolerant, but they do appreciate consistent moisture during the growth and flowering season, especially if a good harvest is desired. Foliage can be trimmed back at any time of the year to control growth and remove dead, damaged and diseased stems and leaves. Fertilize plants yearly for the best show of blooms with a dressing of organic compost applied around the base of the vine. Work the compost into the soil a bit, and then replace the mulch around the base.

Propagation

Thunbergia vines can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your Thunbergia vine, follow the instructions below:

Propagating Thunbergia by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand.
In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new vine.

Propagating Thunbergia by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. If you don't have any potting medium on hand, you can make some. Just mix together equal parts (by volume) moss peat and horticultural-grade sand or grit sand. You will also, after a few weeks, need individual 3-inch pots for each seedling that grows.
Harvest your seeds. They are typically mature in late summer to fall, and are dark brown with pocked seed coats.
Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 10-12 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.

Thunbergia seeds are held inside of the dry fruits produced by vines after flowers have faded. They have pocked surfaces and are typically brown to dark brown in color.