Blue Potato Bush
Lycianthes rantonnetii
NEMBA category
English: Blue Potato Bush, Paraguay Nightshade, Royal Robe
Historical botanical names: Solanum rantonnetii
Lycianthes rantonnetii, known as Blue Potato Bush or Paraguay Nightshade, is an evergreen shrub with a sprawling habit. It bears masses of trumpet‑shaped violet‑blue flowers centred with yellow, followed by small toxic red berries. Its lush, glossy foliage and prolific bloom make it both a decorative plant and a problematic invasive in South Africa.
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Distinguishing features:
Oval bright green leaves, slightly hairy when young, tapering to pointed tips
Trumpet-shaped violet-blue flowers 25–30 mm across with prominent yellow stamens
Red-orange glossy berries ~20–35 mm diameter
Arching grey-brown stems forming a lax mound
Origin:
Native to Argentina, Bolivia, Brazil and Paraguay.
Overall appearance:
An evergreen, woody shrub with sprawling, arching stems. Can be trained as a small tree or climber.
Height:
Reported heights: 1.5 – 2.5 m; up to ~3 m in sub-tropical climates.
Width:
Approximately 1.5 – 2 m spread.
Leaves:
Bright green, ovate to elliptical, entire to slightly undulate margins.
Larger leaves typically 5–7 cm long and 3–4 cm wide.
Young leaves initially hairy, maturing to smooth.
Flowers:
Trumpet or star-shaped; violet-blue with a yellow centre.
Diameter of corolla ~25–30 mm.
Arranged singly or in clusters of 2–7 from leaf axils or stem tips.
Stamens unequal filament length (1–3 mm); anthers 2–4 mm, open by pores.
Flowering season:
In South Africa, flowering occurs mainly during the warmer months (spring to autumn); can bloom almost year‑round in frost‑free regions.
Fruits:
Berries globose to ellipsoid, smooth, colour red-orange, diameter 20–35 mm. Enclosed by persistent calyx.
Seeds:
Multi-seeded; berries contain many small flattened seeds.
Bark:
Stems are grey‑brown, slender and arching; older bark smooth.
Stems:
Slender, arching, initially hairy then glabrous. Internodes around 5 cm.
Soil type:
Prefers humus-rich, well‑drained loam; tolerates neutral to slightly alkaline soils.
Aspect:
Thrives in full sun; tolerates light shade; sheltered sites recommended.
Toxicity:
All parts are considered toxic to humans; ingestion may cause vomiting and stomach discomfort.
Uses:
Ornamental: widely planted for continuous blooms, used as hedge, patio tree or climber
Attracts butterflies, bees and birds to gardens
Ecology:
Flowers supply nectar food to bees and other insects
Berries are consumed by birds, aiding seed dispersal
Can smother indigenous flora, affecting natural ecosystems
Distribution and habitat:
Cultivated and naturalised in frost‑free areas across South Africa
Invades gardens, roadsides and disturbed sites
Derivation of name:
Genus name Lycianthes refers to resemblance to Lycium species.
Specific epithet commemorates French horticulturalist Rantonnet.
Common name “Potato Bush” arises from flower resemblance to potato, despite no relation.
Historical aspects:
Originally described as Solanum rantonnetii in 1859; reassigned to Lycianthes in 1919 based on botanical relationships.
Interesting facts:
It won the Royal Horticultural Society’s Award of Garden Merit in 2012 for its ornamental beauty.
Despite the common name “Potato Bush”, its berries aren’t related to potatoes and are poisonous—so don’t confuse them!
It’s so popular for its blooms that gardeners prize it, yet it spreads into wild areas where it can choke out indigenous plants.
It encourages local wildlife: bees, butterflies, birds—and may even cause native species to suffer due to competition.
You might hear it called “Paraguay Nightshade”—a nod to its country of origin and its floral shape.
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