giant crape myrtle (Lagerstroemia speciosa, (L.) Martyn 1798)

Identity

The giant crape myrtle (Lagerstroemia speciosa (L.) Martyn, 1798), also known as banaba or jarul, is a large deciduous tree in the genus Lagerstroemia, family Lythraceae. Plants of the World Online accepts this binomial. Thomas Martyn published the combination in 1798, based on Munchausia speciosa, published by Linnaeus in 1770. ^{1 5}

Banaba is a Tagalog name for both the tree and the tea made from its leaves, now sold as an herbal preparation far beyond the Philippines. Other English names include pride of India and queen's crape myrtle; bungor is another established name. The old epithet flos-reginae, meaning “queen's flower,” survives in several nineteenth-century herbaria, where it already evoked the profusion of pink panicles. ³

Recognition

NC State describes a tree reaching 12–18 m (39–59 ft) in cultivation, with a broad, symmetrical habit. Some old wild trees grow taller. Wikipedia gives a typical height of about 15 m (49 ft), with a short crown and low trunk supporting a mature spread of 8–12 m (26–39 ft), often wider than the other large trees in the same street planting. ^{2 3}

Outside the flowering season, the bark is the most reliable identifying feature, more consistent than flowers that last only a few weeks. Smooth, thin and pale gray to cream, it peels in patches and is easily injured by even minor mechanical impacts. The simple, elliptical leaves are 8–15 cm (3.1–5.9 in) long. They turn red before falling during the dry season, an unusual pattern for a tropical tree. ³

The flowers stand in broad, upright panicles 20–40 cm (7.9–15.7 in) long. Each has six crumpled petals 2–3.5 cm (0.8–1.4 in) long, ranging from vivid pink to pale mauve. The ensuing capsule is woody and oval, changing from green to brown and finally black when fully ripe; it often remains on the tree long after the flowers have fallen. ³

Useful taxonomy

POWO recognizes two subspecies within Lagerstroemia speciosa. The typical subspecies is by far the more common in horticulture. Lagerstroemia speciosa subsp. intermedia (Koehne) Deepu & Pandur. is restricted to southwestern Yunnan and Myanmar. Their differences are mainly floral and little documented outside regional floras. ¹

Several historical names occur in botanical synonymy:

• Munchausia speciosa L., the basionym published by Linnaeus in 1770
• Lagerstroemia munchhausia L. ex Forsyth f., an illegitimate name
• Murtughas speciosa (L.) Kuntze

The genus also includes Lagerstroemia indica, a much smaller shrub or small tree hardy into temperate climates. Both species are sometimes called lilas des Indes in French. The full scientific binomial is the reliable reference, rather than this shared common name. ^{5 7}

Habitat and distribution

The native range spans tropical Asia, from southern Yunnan in China to India (the Western Ghats, Assam and West Bengal), Myanmar, Thailand, Vietnam, Cambodia, Malaysia, Indonesia, the Philippines and Melanesia. ^{1 3}

Banaba grows in wet tropical lowland and mid-elevation forests, often beside watercourses or in temporarily flooded ground. It tolerates waterlogged soil for longer than most large ornamental trees. NC State recommends rich, deep alluvial loam that remains warm and moist throughout the year, with a pH of 5.5–7.5. The ideal temperature for flowering is 22–32 °C (72–90 °F), above the range tolerated by most large temperate street trees. ²

Widely grown outside its native range, particularly as a street tree in Southeast Asia, it has also been introduced to Australia and the Caribbean. Its hardiness is limited to USDA zones 10–11. In France, outdoor cultivation is confined to overseas departments and territories: it cannot withstand mainland winters in the ground. ^{2 6}

Life cycle and reproduction

Flowering begins 3–5 years after planting, chiefly from April to June, with a second flush in July and August depending on summer warmth. The fruit then ripens from November to January in capsules that gradually turn black. These month-based observations depend on the climate and hemisphere. ³

Propagation is almost exclusively by seed. NC State and Wikipedia agree that seeds germinate readily in warm, moist growing media at 25–30 °C (77–86 °F). Unlike Lagerstroemia indica, Lagerstroemia speciosa has few named cultivars routinely propagated from cuttings. ^{2 3}

The dense, durable wood is reputed to rank just below teak in strength in several parts of South Asia. This reputation explains its traditional use in structural carpentry and boatbuilding where the tree grows wild. ³

Uses and risks

Outside Asia, the main use is ornamental: street plantings, parks or specimen trees valued for summer flowers and winter bark. In the Philippines, Taiwan and Japan, dried leaves are used to prepare a tea also called banaba, promoted by the Philippine Department of Health among its recognized medicinal plants. ³

Pharmacological research has isolated several compounds from leaf extracts, including corosolic acid. Their effects on blood glucose and fat metabolism have been studied in laboratory animals. Klein and colleagues review this work without establishing a validated therapeutic use in humans at that stage. ⁹

The ASPCA lists Lagerstroemia indica as non-toxic to cats, dogs and horses. Its entry concerns a different species from banaba (Lagerstroemia speciosa) and does not by itself establish banaba’s safety. In humans, however, banaba seeds are described as narcotic, and the bark as purgative when large amounts are ingested. These traditional uses involve controlled amounts rather than unrestricted consumption. ^{8 3}

Varieties, lookalikes and related plants

Few named horticultural cultivars exist for Lagerstroemia speciosa. The indica × fauriei hybrids dominate the temperate market instead. Subspecies intermedia remains primarily a regional flora reference rather than a garden selection. ¹

The most likely confusion is between Lagerstroemia speciosa, a large tropical tree with leaves 8–15 cm (3.1–5.9 in) long, and Lagerstroemia indica, a temperate shrub or small tree with much smaller leaves. Their shared French name, lilas des Indes, cannot distinguish them in the field. Mature size and hardiness provide the distinction. ^{2 4}

Other large tropical trees with spectacular flowers share its role in street plantings, including jacaranda (Jacaranda mimosifolia) and royal poinciana (Delonix regia). Neither belongs to the Lythraceae, and neither shows the peeling bark characteristic of Lagerstroemia. ³

Main sources

• Plants of the World Online / Kew, Lagerstroemia speciosa (L.) Martyn
• NC State Extension Gardener Plant Toolbox, Lagerstroemia speciosa (Giant Crape Myrtle, Queen's Crape Myrtle)
• Wikipedia (EN), Lagerstroemia speciosa
• Wikipédia (FR), Lagerstroemia speciosa
• ITIS, Lagerstroemia speciosa (L.) Pers., TSN 27111
• USDA PLANTS Database, Lagerstroemia speciosa (LASP)
• GBIF Backbone Taxonomy, Lagerstroemia speciosa (L.) Pers.
• ASPCA, Crape Myrtle (Lagerstroemia) toxicity entry
• Klein et al., 2007, Antidiabetes and Anti-obesity Activity of Lagerstroemia speciosa, Evidence-Based Complementary and Alternative Medicine