The summer annual weeds are starting to emerge and I am using this blog over the next few weeks to introduce readers to the seedlings of important species.

Black nightshade (Solanum nigrum) is an annual (or sometimes a short-lived perennial) species that is common throughout much of the state inhabiting: tree and vine systems, agronomic and horticultural crop fiels, roadsides, gardens, and other disturbed sites. 

The seedlings have cotyledons that are ovate (oval) to lanceolate (lance-shaped) with pointed tips that can become purplish in color. Leaves are ovate to triangular in shape, also with pointed tips. Early leaves have simple margins whereas older leaves possess margins that are wavy to shallowly-toothed; eventually leaves become dull, dark green in color. Cotyledons, leaves and stems have short nonglandular hairs and some glandular hairs on them.

Images are included in a printable PDF document at the end of the post. For more information about black nightshade, please connect to the following UC IPM website: http://ipm.ucanr.edu/PMG/WEEDS/black_nightshade.html

Figure 1. A recently emerged seedling of black nightshade; note the paired, lanceolate cotyledons. Also note the fine hairs on both the cotyledons and the leaves.

Figure 2. A seedling of black nightshade showing lanceolate cotyledons that have become purple-tinged and hairy, triangular leaves.

Figure 3. A more mature seedling exhibiting leaves that are dark green in color and possessing smooth margins.

Figure 4. A mature, flowering black nightshade; leaves are dark green in color and the margins are wavy.