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Rubiaceae

In this series, I aim to give you a quick introduction to some of the plant families found in the UK. Learning to identify plant families is a great help in identifying individual plant species you come across – if you know the family, then you know where to start looking for the species in a guide, and identifying the family is an achievement in itself. Plants are classified into families based on characteristics that they share; this is then narrowed down further into genera and then into species. So, the way to identify a plant’s family is to know these characteristic features. Today we're going to look at the Rubiaceae - the bedstraw family. The Rubiaceae are found throughout much of the world, with their main stronghold in the tropics. These tropical species include Coffea arabica (the coffee plant) and Cinchona pubescens (the cinchona tree) from which the drug quinine, the main treatment for malaria for many decades, is extracted. The conservatory plant Gardenia jasminoides is part of this family, too. While most of the approximately 13,150 species are shrubs and trees, the species found in the UK are herbaceous. There are both annual and perennial species and they have a distinctive set of characters. The UK species include the common Galium aparine (sticky Willie or cleavers) - the one that sticks to your clothes. If you've never stuck this plant to someone unsuspecting, then you're missing out. It can also be eaten as a vegetable after cooking. Galium odoratum is sometimes grown as a garden plant and has a sweet scent when dried. Because of this, it was used in the past as a strewing herb to make rooms smell better. There are a number of other Galium species too, plus representatives of other genera, like Cruciata laevipes (crosswort). The flowers of the UK Rubiaceae are small, sometimes very small, and mostly white or yellow. They emerge from the axils of the leaves or form loose clusters at the end of the stems. The flowers are regular in shape - also known as actinomorphic, or symmetrical in more than one direction. They have either 4 or 5 petals, which are partially joined, and the sepals are small or missing altogether. There are 4 or 5 stamens to a flower and the plants are pollinated by insects. The inferior ovary, attached below the rest of the floral parts, becomes a set of paired nutlets in most species, though Rubia peregrina (wild madder) forms black berries. These fruits may be hooked, warty, wrinkly or smooth. The hooked ones, like those of Galium aparine, are adapted to catch on animal fur for dispersal - though they do just as good a job of attaching themselves to clothes. The leaf arrangement of these plants is very recognisable. They have whorls of leaves at intervals among their stems. Strictly speaking, only two of the green organs in each whorl are officially leaves, the rest being leaf-like stipules, structures found at the base of leaf stalks in many plants. However, for practical purposes, look for whorls of leaves forming rings at the stem nodes. The leaves are simple, meaning they are undivided. Each species has a typical number per whorl, and the leaves of many species have pointed prickles on their margins. Which direction these prickles point is important for identification for some species. The stems may be covered in prickles too, and they are 4-angled to a greater or lesser degree, with some being more or less square in cross-section and some square with ridges running down them at each corner. So, if your plant has small flowers in white or yellow, paired fruits, whorls of leaves around the stem and stems with 4 angles, then it looks like it's in the Rubiaceae.The next time you're out for a walk, keep an eye open for these 3 species: • Galium aparine (sticky Willie, cleavers): a light green, scrambling plant with prickles on its stems, leaves and fruits that allow it to hook onto clothes, fur and skin • Galium verum (lady's bedstraw): with dark leaves and frothy clusters of yellow flowers • Cruciata laevipes (crosswort): with 4 leaves per whorl and yellow flowers in the leaf axils [Note, botanical names should always be written in italics (or underlined if handwritten)]