Columbian Petunia (Suessenguthia multisetosa)

Dragonfly Lake (near Bayfront Shuttle Stop)

Suessenguthia multisetosa, commonly known as the Columbian petunia, is a striking but little-known member of the Acanthaceae, the same plant family that includes several other South and Central American plants frequently grown as ornamentals in Singapore. These include the purple, pink, or white-flowered Mexican petunia (Ruellia simplex), the red-bracted shrimp plant (Justicia brandegeeana), and the nerve plant (Fittonia albivensis).

The genus Suessenguthia contains eight species found across the Andean foothills and adjacent Amazonia in Bolivia, Peru and western Brazil. The Columbian petunia is endemic solely to Bolivia, where it occurs in the north-central and eastern parts of the country, across the departments (administrative subdivisions) of Beni, La Paz and Santa Cruz. It is found in the Andean foothills, moist tropical forests, and the seasonally dry forests and savannas of Bolivia’s Chiquitania region, generally between about 200 and 700 m elevation.

Depending on growing conditions, the Columbian petunia develops as a large shrub or small tree-like plant about 2–6 m tall. Its young stems can be rather fragile and may require support when cultivated. The opposite, ovate leaves are hairy and measure approximately 15–18 cm long and 5–10 cm wide, with young foliage often emerging dark reddish green before maturing to green.

The plant is especially noticeable when flowering. Its purple to pink flowers are borne in clusters and can reach approximately 6–8 cm long and 2–4 cm wide. Their broad, tubular form gives them a distinctly petunia-like appearance, despite true petunias belonging to a completely different family, the tomato family (Solanaceae). One of its most distinctive features is highlighted in its species name multisetosa, referring to the multiple hairy, long, narrow and bristle-like, or setose, structures surrounding the flowers, particularly the floral bracts and calyx.

One of the most interesting aspects of the Columbian petunia is its pollination biology. Several species within Suessenguthia have flowers adapted for hummingbird pollination, but the Columbian petunia is bee pollinated. Studies of the genus suggest that an evolutionary shift from bee to hummingbird pollination was accompanied by changes in flower shape and inflorescence structure. 

Bee-pollinated flowers tend to be shorter, paler and more funnel-shaped, with broad spreading lobes and stamens held within the corolla, while hummingbird-adapted flowers are generally longer, tubular and more intensely coloured, usually in bird-attracting colours of red, orange, or yellow, with reduced or recurved lobes and protruding stamens. The flowering pattern also shifts from many flowers opening around the same time, supporting intense bee visits over a short period, to fewer flowers opening sequentially over a longer period, supporting hummingbird visits over several weeks to months. Bee pollination is thought to represent the ancestral condition in the genus, with hummingbird pollination evolving later. This makes the Columbian petunia an interesting basal example of the bee-pollinated condition within a group of close relatives adapted to hummingbird pollination.

The species is also considered Vulnerable by the IUCN. Although it can be locally abundant in Bolivia’s Chiquitano dry forests, habitat loss and degradation caused by agriculture, cattle ranching, logging, urban expansion and fire threaten parts of its natural range. Its conservation assessment drew upon 63 herbarium specimens collected between 1916 and 2017, providing more than a century of botanical records. Fortunately, populations also occur within protected areas. With its petunia-like blooms, bristly floral structures, unusual pollination story and restricted natural range, the Columbian petunia is far more botanically interesting than its ornamental appearance might first suggest.

Step outside the conservatories and look out for these vivid blooms around Dragonfly Lake, right after the Bayfront shuttle service, where the Columbian petunia can be appreciated up close.

This article is part of our What's Blooming series.