Sub-species : There are two sub-species, both commonly called Black Nightshade: Solanum nigrum subsp. nigrum and Solanum nigrum subsp. schultesii. Whereas Black Nightshade (either sub-species) is shown as widespread especially in the south of the UK, those which have been identified to sub-species level are not shown with the same combined distribution (probably because no one around the areas they are missing from have identified them to sub-species level). Thus ssp. nigrum is shown as more confined to the South and East whereas ssp. schultesii is much less widespread and confines itself mainly to the SE of England. Clearly, the sub-species maps are not up-to-date, but that is true for most distribution maps of any plant having sub-species.
Some similarities to : Bittersweet (both are of the Nightshade Family, but Black Nightshade has white-petalled flowers whereas Bittersweet has purple ones. The berries of Bittersweet, green at first as are those of Black Nightshade, turn red, whereas those of Black Nightshade turn black. The flower stems of Bittersweet bifurcate in two's, whereas those of Black Nightshade split into several at the same node.
Uniquely identifiable characteristics
Distinguishing Feature : The white five-petalled flower with swept-back petals and a central yellow column of five stamens bunched together into seemingly one, together with the small black berries.
Habitat includes waste places and farmland.
There are two sub-species of Black Nightshade, one native, the other not:
The above plants all correspond to the ssp. nigrum sub-species.
Black Nightshade (Solanum nigrum ssp. nigrum), a native with non-glandular often sparse hairs that are appressed to the surfaces.
Black Nightshade (Solanum nigrum ssp. schultesii), an introduced and naturalised plant with glandular hairs that are patent (stick out).
Like most plants belonging to the Nightshade Family, Black Nightshade contains poisonous solanines, in this specific case
Solamargine. Solanines are poisonous steroidal alkaloids and steroidal glycosidic alkaloids.
SOLANINES WITHIN BLACK NIGHTSHADE
Solamargine is found not only in Black Nightshade but also in Thorn-Apple (Datura stramonium) (both of which belong to the Nightshade Family) and has potent cytotoxic activity on both hepatocytes and skin cells, initiating cell death by apoptosis. It also inhibits the growth of cancerous cells. Solamargine together with a symbiont Solasonine (another steroidal glycosidic alkaloid) has found use in a cream for external application to treat malignant melanomas (skin cancers), benign tumours and keratoses of the skin. Solasonine (not shown) is also found in Thorn-Apple (Datura stramonium).
Solasodine is a steroidal alkaloid and the aglycone (without sugar moieties) of the steroidal glycosidic alkaloid Tomatine found in un-ripe (green) Tomatoes (which is another member of the Nightshade Family). Tomatine is shown below for illustration purposes only, as far as is known it does not occur in Black Nightshade. Note how there is only a single methyl group (CH3) difference between Tomatine and Solamargine (in the upper right hand corner).