Clerodendrum thomsoniae aka Bleeding Heart Glorybower

As a climbing vine, Clerodendrum thomsoniae can produce stems up to 7 metres long when given support, though plants in shrub form typically reach 1–2 metres. In typical cultivation it is maintained at around 4 metres tall with a spread of approximately 1.5 metres. Mature plants in containers or trained indoors usually reach 12–15 feet (3.6–4.6 m).

Clerodendrum thomsoniae is native to tropical west Africa, from Senegal in the west through Nigeria and Cameroon to the Democratic Republic of Congo. It has since naturalised in parts of the Americas, the Galapagos Islands, and Australia following escape from cultivation.

This plant is frost-tender and requires a minimum temperature of 10–13 °C (50–55 °F). In temperate climates it must be grown in a frost-free greenhouse, conservatory, or as an indoor houseplant. During winter dormancy, daytime temperatures of 60–65 °F (15–18 °C) with slightly cooler nights are recommended, and watering should be reduced.

Clerodendrum thomsoniae originates from tropical west Africa and thrives in humid conditions. It is best grown in a sunny and humid greenhouse or conservatory in temperate regions; low humidity in indoor environments can contribute to spider mite infestations.

Apply a balanced fertilizer regularly during the active growing season. Withhold fertilizer entirely during the winter dormancy period when growth slows or stops.

During the growing season (spring through autumn), water regularly and feed with a balanced fertilizer. In winter, allow the plant a rest period: reduce watering, withhold fertilizer, and keep temperatures slightly cooler (around 60–65 °F / 15–18 °C by day, 5–10 °F cooler at night). Prune in late winter or early spring before new growth begins, removing overcrowded and far-reaching shoots to encourage vigorous flowering growth.

Flowers are bicoloured: a striking pure white to pale-purple five-lobed calyx (~2.5 cm across) surrounds a vivid red five-lobed corolla (~2 cm). Blooms appear in clusters of 8–20. In the northern hemisphere, flowering typically occurs June–August. Black fruits develop after the flowers fade. The plant received the RHS Award of Garden Merit (confirmed 2017).

Molecular work has characterised the complete chloroplast genome of C. thomsoniae (Chen et al., PLoS One, 2023), confirming its closest phylogenetic relative is Volkameria inermis within Lamiaceae. No widely grown named cultivars are documented in the consulted horticultural sources — the species is generally cultivated in its wild form.

Clerodendrum thomsoniae is suitable for outdoor cultivation year-round only in USDA zones 10–12 (frost-free tropical and subtropical climates). In cooler temperate regions it can be moved outdoors during warm summer months and brought back under glass before temperatures drop below 10–13 °C. It has naturalised outdoors in parts of the Americas, Galapagos, and Australia.

Prune annually in late winter or early spring, before new growth begins. Cut back severely, removing old overcrowded shoots and any far-reaching stems to keep the vine in bounds and encourage vigorous, floriferous new growth. Annual pruning also helps train the plant along supports such as a trellis or obelisk.

Clerodendrum thomsoniae can be propagated from seed, root cuttings, or by dividing suckers. Stem cuttings taken in spring or early summer are also a common method in cultivation.

The most common pests are spider mites (red spider mite) and whitefly, especially in greenhouse or conservatory environments. Mealybugs are also reported. Maintaining good humidity and air circulation helps reduce spider mite risk. No specific disease issues were documented beyond general susceptibility to these common greenhouse pests.

Clerodendrum thomsoniae has no known edible parts. No culinary use is documented in any of the consulted sources.

Traditional medicinal uses are reported from West Africa: the leaves and flowers are pounded and applied topically to bruises, cuts, skin rashes, and sores. Macerated leaves are also used as a shampoo to prevent scalp scaling and treat dandruff. No clinical evidence or formal pharmacological studies specifically on C. thomsoniae were identified in the consulted sources; broader genus research covers antimalarial, antidiabetic, and anticancer activity.

The primary use of Clerodendrum thomsoniae is ornamental — it is widely grown as a decorative houseplant, conservatory climber, and hanging basket subject for its spectacular bicoloured flowers. Traditional cosmetic use of macerated leaves as a hair shampoo is reported from West Africa. No significant commercial or industrial uses are documented.