The Nightshades

Deadly Nightshade: Atropa belladonna
AKA: Belladonna, Dwale
Origin: Native of southern England and central Europe, southern and western Asia. Rare in Scotland.
Toxicity: All parts poisonous, especially roots.
Part Used: Berries
Lore: Named after Bellona [war goddess.] At certain times it takes the form of a beautiful enchantress whom any that look upon her will die.
Plant belongs to the devil who tends to it all year long, except on Walpurgis when he is preparing for Witches' Sabbat.
Atropa comes from Greek Atropos, one of the Fates who held the scissors to cut the thread of human life.
Magick: Beauty magick. To consecrate ritual tools made of lead. Has affinity with Onyx. Lunar magick. Spell workings related to Death.
Other: Berries are black.
Bittersweet: Solanum dulcamara
AKA: Woody Nightshade, Felonwort
Origin: All over.
Toxicity: Slightly poisonous.
Part Used: Berries.
Lore: Shepherds hung it as a charm around the necks of their animals as protection from evil.
Other: Berries are red.
Black Nightshade: Solanum nigrum
AKA: Garden Nightshade, Petty Morel
Toxicity: Berries are poisonous, especially to children.
Origin: All over.
Other: Berries are black.

Note: Bittersweet and Black Nightshade are of the Solanacae family and related to Henbane, Datura, Mandrake, Capsicum [Red Pepper], Tomato, Potato.
In magick, all Nightshades may be used interchangeably.