How to Grow Thunbergia - Planting & Caring

By Sharon & Team   /   Shrubs Category   /   2023

Thunbergia, also known as black-eyed Susan, is a beautiful flowering plant that is easy to grow. Thunbergia plants are native to Africa and Asia, and they have become popular houseplants in many parts of the world. The plants produce large, trumpet-shaped flowers that are typically white or yellow with a black center. Thunbergia plants are easy to care for and can be grown in a variety of climates.

How to Grow Thunbergia - Planting & Caring

Growing Easiness

Is it easy to grow Thunbergia plant? While it is easy to grow this plant, it is necessary to make sure it is cool during winter. This can be done by either keeping it in a cool location or by covering it with a light cloth.

Plant Size

How big can it be? The average Thunbergia plant is 1.8-3 m in height. However, there are some climbing species that can reach up to 6 m in length.

Growth Rate

How fast is the growth? Unless you live in a tropical climate, you'll need to grow Thunbergia indoors. These evergreen perennials are fast growers that can reach 6 to 10 feet in length. They're easy to propagate from stem cuttings, so if you want to create more plants, it's a simple process. Place the cuttings in a glass of water and wait for roots to form. Once they do, you can pot them up and enjoy your new plants.

Thunbergia Basic Knowledge

Plant Form Shrub
Family Acanthaceae
Origin Tropical Africa

Lifespan, Perennial or Annuals

How long is the lifespan? Since they live relatively long, it is best to rejuvenate the plant every few years from cuttings or by cutting it back. This will keep the plant looking nice and prevent it from losing its decorative properties. Thunbergia can also be grown as an annual.

Ideal Temperature

What is the ideal temperature? Unless you live in a tropical climate, you should bring your plants indoors when the temperature starts to drop at night. Most Thunbergia can tolerate a little light frost, but not for extended periods. The optimum temperature for most species is 18-21°C. They will still do well enough at 16°C, but growth will be slower. If the temperature drops to 10°C, the plants will start to suffer.


What about the humidity? So, the level should be 50% for the Thunbergia plant to be at its best, although it can cope with drier air. It's often best to focus the spray on the leaves, avoiding getting water on the flowers.

Light Requirement

What amount of light this plant needed? Because it is native to Africa, the plant needs a bright diffused light. It can grow on a southern window with a shade from the midday sun, or on an east or west window.

Soil Composition

What is good soil for Thunbergia? The best soils for Thunbergia are well-draining and consists of one part of sod land, one-half part of coarse-grained sand or perlite, and one part of humus earth. The pot for the plant should always have an opening.

Watering Time

How much I must water Thunbergia? known as black-eyed Susan, this plant is a vining annual that is easy to grow. Black-eyed Susan is not drought tolerant and requires ample water during the growing season. Water at room temperature, 2-4 times per week during the summer and every 12-14 days during the winter. The soil should be moist, but not soggy. Allow the soil to dry out slightly between watering.

Fertilizing and Nutritient

About fertilizer. Because this plant blooms best when potassium-rich fertilizer is used, it's a good idea to fertilize every two weeks with a liquid fertilizer once buds appear.


How to reproduce Thunbergia? The best time to take cuttings is in spring. The cuttings should be 8-10 cm long. The lower leaves should be removed before planting the cutting. The cutting should be pre-treated with hormones and then placed in a mixture of moist sand and peat. The mixture should be covered with a polyethylene film. After rooting, the plant cutting should be transplanted and the top should be pinched for better branching. Thunbergia can also be propagated by seeds. The temperature should not be below 64.4-68 degrees Fahrenheit. The seeds should be sown in February-March in a mixture of peat and sand. The mixture should be kept under a film. Germination occurs after 2-3 weeks. When the seedlings become stronger, they should be transplanted into 6-cm pots. Later, they should be transplanted into 10-cm pots. Thunbergia usually blooms 3.5-4 months after sowing.


Why Thunbergia won't bloom? Since it is a tropical plant, it blooms all year long. The flowers are orange or purple, tubular, and up to 7 cm long.

Transfer or Repotting

How much I must water Thunbergia? The best time to replant Thunbergia is in the spring, when you can see the roots coming out of the drainage hole. Make sure that the plant has good drainage to avoid problems.

Caring The Thunbergia

How to care the plant? The best way to display a Thunbergia is in a hanging basket where its long shoots can cascade down, however, it can also be trained to grow up a special support. It’s important to ensure that the shoots are evenly distributed along the support to prevent them from tangling. The plant requires good ventilation during the summer months but be careful that drafts don’t spoil the leaves. To encourage better branching, it’s necessary to nip young plants. After 2 years of growth, one third of the shoot should be cut back. Old, stretched plants will bloom worse. It’s also important to remove wilted flowers in a timely manner. The plant requires regular hygienic procedures such as rubbing the leaves with a damp cloth.

Pests & Challenges

What is the challenge when caring Thunbergia plant? The plant is affected by spider mites, scutes and whiteflies. Most often, the lack of flowering is associated with insufficient lighting. Spots on leaves can appear due to fungal infection when the plant is kept in conditions of low airing and high humidity. To save the plant, you need to remove the damaged leaves and use fungicides.

Toxic & Poisonous Type

Are Thunbergia poisonous? Eventually, all parts of the Thunbergia plant are toxic if ingested by humans or animals. The sap from the plant can cause irritation and blistering of the skin. The plant is also known to be poisonous if ingested, and can cause vomiting, diarrhea, and abdominal pain.