Learn how to identify common plant families in (more or less) five minutes.

In this series, I aim to give you a quick introduction to some of the common plant families found in the UK. Learning to identify plant families is a great help in identifying individual plant species you come across. Plants are classified into families based on characteristics that they share; so, the way to identify a plant’s family is to know these characteristic features.

Today we're going to look at the Solanaceae, or nightshade family. The nightshade family encompasses around about 2500 species. These are distributed worldwide, although the greatest number and variety are found in South America. This is a family of herbs and shrubs, with some trees. A fair number of them are climbing or scrambling. They range from annuals through to perennials.

This family has great economic importance because many of the species are used for food. A lot of our well-known vegetables and fruits are Solanaceous plants. Solanum tuberosum, the potato and, S. lycopersicum, the tomato, are two of these, with Physalis peruviana, the Cape gooseberry, and Lycium barbarum, the goji berry, are another couple of examples. Many species the nightshade family contain various chemical compounds that make them poisonous, in some cases highly toxic: Atropa belladonna, the deadly nightshade, is a case in point. These chemicals are also why extracts from some of these plants have led to development of medicinal drugs. They also have risky hallucinogenic properties, and it’s thought that plants such as Mandragora autumnalis, the mandrake, were connected with the legends of witches flying. This family also contains ornamental species like Solanum crispum, the potato vine, Brugmansia, Angel’s trumpets, and Nicotiana alata, jasmine tobacco. Nicotiana tabacum is the source of tobacco.

There aren’t very many species of Solanaceae in the UK. The species that are here are either herbs or shrubs, and are annual or perennial.

The overall appearance of Solanceae flowers is quite recognisable once you get used to them. Their flowers are regular and wheel-shaped, with 5 sepals joined together and 5 petals joined together into various lengths of tube. The petals tend to be either purple or white. There are 5 stamens. In the genus Solanum the stamens are grouped together to form a clump or spike in the centre of the flower. These stamens are adapted to buzz pollination by bees, a process where a bee grabs onto the flower onto the flower and vibrates at a frequency that causes the tops of the stamens to open and spray out pollen. In general this family is insect-pollinated.

The ovary of the flowers is superior, so is attached above the point that the rest of the floral parts are. Then fruits that develop from fertilised flowers are berries in most of the UK species, though a couple of species produce capsules that break open to release the seeds. The berries are presumably eaten and dispersed by animals.

The leaves of plants in this family are arranged alternately on the stems, and are generally simple, with margins ranging from entire to lobed, sometimes of the same plant. The species with the widest range in the UK, Solanum dulcamara, the woody nightshade or bittersweet, has a scrambling habit with long, flexible stems.

So, if the plant you’re looking at has purple or white, wheel-shaped flowers, with 5 joined petals and sepals, perhaps with the stamens joined in a spike, and a berry or capsule fruit, with alternate, simple leaves, it just might be in the Solanaceae.

See if you can spot any of these 3 species:
• Solanum dulcamara, bittersweet: a scrambling plant that has deep purple flowers with yellow stamens and berries ripening to red.
• Solanum nigrum, black nightshade, an upright plant with white petals and black berries.
• Atropa belladonna, deadly nightshade, a large plant with purplish-brown, bell-like flowers and glossy black berries. And no matter how good they look, don’t eat ‘em…

[Note, botanical names should always be written in italics (or underlined if handwritten)]