Reproducing by seed and by underground rhizomes.
Stems erect, 60-100cm high, with a few branches near the top, covered with tiny, star-shaped hairs, each having 1 point longer than the rest (visible only with magnification), and scattered, long, hard, sharp spines often 5mm long.
Leaves alternate (1 per node), elliptic in outline but shallowly to deeply lobed with 2 to 5 rounded or sharp-pointed lobes on each side, finely hairy on both surfaces with star-shaped hairs plus several, long, hard spines, at least on the underside along the midrib and main veins.
Flowers arranged in 1 or more short racemes at the ends and sides of branches in the upper part, corolla pale purplish to white, 1.5-2cm across, with 5 stamens joined in a central column about 6mm long; berry smooth, yellow at maturity and about 1.5cm in diameter. Flowers from July until autumn.
Horse-nettle is found in scattered localities throughout southern Ontario, usually in sandy soils, in grainfields, pastureland, waste areas and occasionally in gardens.
It is distinguished by its harshly spiny stems and leaves, lobed leaves, large, white to purplish flowers, smooth yellow berries, and its spreading perennial rhizomes which enable this plant to form thick patches.
Horsenettle. A. Top of plant. B. Portion of horizontal rhizome producing new aboveground shoot.
Closer view of horse-nettle.
Stem of horse-nettle covered with tiny hairs and sharp spikes.
Lobed leaf of horse-nettle.
Surface of horse-nettle leaf, covered with fine star-shaped hairs and hard, long spines.
Underside of horse-nettle leaf (note hard spines).