Bog Plants: Our Peatland Specialists

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Long regarded as unproductive and inhospitable, the UK’s peat bogs have suffered centuries of drainage, afforestation, burning, overgrazing and peat harvesting. More recently, though, we have begun to realise just how important they are as carbon sinks and refuges for some of our rarest wildlife. This includes some of our most specialised plant species, a few of which don’t grow anywhere else. So, although I’ve talked a little bit about bogs before, in this post, after a quick introduction to what makes a bog a bog, we’ll meet some of my favourite bog plants.

Bog Basics: What Is a Bog?

Peat bogs form in temperate climates in places with lots of rain but poor drainage and low levels of evaporation. This creates a waterlogged environment which prevents dead vegetation from rotting completely due to the lack of oxygen. Over thousands of years, the partially rotted plant matter is compressed by the weight of further vegetation on top and forms peat. In some places, this peat can be metres deep. The peat acts like a sponge, holding on to water and maintaining the waterlogged conditions, thus creating more peat. These thick layers then cut off the bog’s surface from any nutrients in the bedrock and groundwater. As a result, bog plants have to be able to survive in a low-nutrient environment that is naturally acidic and subject to high levels of saturation.

Forsinard bog — Caithness’ Flow Country is one of the largest intact areas of blanket bog in the world

Most peat bogs began forming at the end of the last ice age as the climate became wetter and warmer. In the UK there are three types of bog: blanket, raised and quaking bogs. Our wet, temperate climate is, currently, perfect for bog formation and we hold a disproportionately large amount of the world’s bogs. In fact, the UK and Ireland between them have over 20% of the world’s blanket bog. Centuries of loss to harvesting for fuel or garden peat, as well as overgrazing and drainage for farming, forestry and development, have reduced them greatly, however. Fortunately, we are now realising how important bogs are. In particular, they are essential in helping to combat climate change. Peat traps huge volumes of CO₂ and methane, potent greenhouse gasses. Bogs are actually more efficient at storing carbon than rainforests. This means that protecting and restoring them, and the plants living in them, is more important than ever. Now, let’s meet those special plants.

Bog colours — Mosses, lichens and heathers dominate most blanket bogs

Sphagnum Mosses

The most important plants when it comes to bogs are its sphagnum mosses. Because most grasses and sedges need more nutrient-rich environments, sphagnums dominate our bogs. As a result, peat is largely composed of semi-decayed and compressed sphagnum moss. Incredibly, living moss can hold up to 20 times its own weight in water. Research shows that this can be hugely beneficial when it comes to flood prevention in some areas. Moss below the surface also stays moist, preventing organic decay, forming more peat and locking up large amounts of CO₂ in the process.

Globally, there are approximately 380 species, while in the UK we have over 30. Most are difficult to tell apart. They bring an array of beautiful colours to our bogs, forming a spongy, wet carpet of reds, oranges, pinks, greens and yellows. A host of invertebrates live amongst the mosses, including spiders, springtails and beetles. Sphagnum mosses also have anti-septic qualities and because they also absorb blood have been used for wound-dressing for centuries. Large volumes in particular were used during World War I.

Sphagnum bog plants — Some sphagnum species, such as this (probable) acute-leaved bog-moss, form dense hummocks

Common and Hare’s-tail Cottongrasses

Both of these species are actually sedges rather than grasses. Common cottongrass produces three to seven fruiting bodies on the end of each stem, each looking like a drooping ball of cotton wool. They usually appear in June and July after the more inconspicuous greeny brown flowering heads. The sight of a host of bobbing cottongrass heads across a bog in summer is a beautiful transformation of an otherwise superficially bleak landscape. Like sphagnum mosses, they were used as wound dressings in World War I.

Common cottongrass bog plants — Common cottongrass produces several drooping heads on a single stem

Hare’s-tail cottongrass has a single, more compact fruiting body held more upright on the end of each stem. This makes it look more like the hare’s-tail of the name. The bulk of the fruiting period tends to be over by the end of June, while common cottongrass’ fruiting extends later into July and August. Unlike its relative, it grows in tussocks rather than singly and has much thinner leaves. Both plants, though, like acid bogs and heaths and can cover extensive areas of suitable habitat.

Hare's-tail cottongrass bog plants — Hare’s-tail cottongrass is tussock-forming

Common Deergrass

Another member of the sedge family, deergrass grows in dense tussocks up to 30 centimetres high. Hundreds of smooth cylindrical stems make up each tussock. Each stem is then topped with a set of yellow, tufted anthers in May and June. These anthers are where the plant produces pollen and appear in a spiral shape when viewed from above. A brown fruiting body, or nut, follows once flowering is over. Interestingly, deergrass is able to withstand both high deer grazing levels and peatland burning due to the density of its tussocks . Where sphagnum mosses dominate, however, they tend to grow only at the edges of bogs. It also readily hybridises with its much rarer relative, northern deergrass.

Purple Moor-grass

Unlike the misleadingly named species above, purple moor-grass is indeed a member of the grass family. It usually forms tussocks, densely packed with numerous individual stems. As with deergrass, this helps make it more resistant to peatland fires. Where conditions are favourable, it can reach heights of 100 or 120 centimetres. It flowers between July and September, producing long, thin, purple inflorescences. Later in the year, the blue-green leaves fade to a creamy white colour. As well as being a common bog plant, purple moor-grass grows in a variety of lowland habitats with acidic soils such as fens, heaths and wet meadows. It is also popular with gardeners as an ornamental plant because it forms clumps that can be easily managed and provides a range of colours across summer and autumn.

Common Butterwort

Because bogs are acidic and nutrient-poor, some bog plants have evolved inventive ways to supplement their diets. Common butterworts are one such plant. To make up for the nutrient shortfall, they became carnivorous. Butterworts excrete a sticky substance from their leaves that first attracts insects and then traps them. The plant then curls its leaves around their prey and digests them. Found in bogs, fens and other damp habitats, they are more common in the north and west of the UK. The plant flowers between May and July and is easy to identify. A pale green star of leaves radiates from the base of the plant and two or three slender stalks each carry a tubular purple flower. The name comes from the belief that butter was protected from evil if the plant was rubbed on a cow’s udders.

Round-leaved Sundew

The UK’s three sundew species are also carnivorous, with the round-leaved our most common species. The plant’s pale green, lobed leaves are covered in small, red hairs, each with a drop of sticky insect-attracting liquid at the end, the ‘dew’ of the name. When an insect lands and becomes trapped, the leaf curls round it and the prey is digested. Round-leaved sundews are tiny plants and easily missed amongst sphagnum mosses and moor grasses despite the deep red colour the sticky hairs give it. In summer, they produce thin flower stalks topped with tiny white or pink flowers. These only open briefly on sunny days. Our two other species of sundew, great and oblong-leaved, have more paddle-shaped leaves and are much less common.

Great sundews, like this one, have longer, more spatulate leaves

Cross-leaved Heath, Bell Heather and Ling

All three of the UK’s native heather species are common bog plants. Of the three, cross-leaved heath is the biggest fan of wet, boggy areas. This species arranges its closed bell-shaped flowers in clusters that droop to one side of a longish stem. These flowers are usually pale pink, but the exact shade varies. Its short, thin leaves are in groups of four around the stem, forming a cross if viewed from above. Like all our heathers, they are popular with a range of pollinators, including a number of bee and moth species.

Cross-leaved heath bog plants — Cross-leaved heath’s flowers droop in a cluster to one side of each stem

Ling or common heather is also happy to grow in wetter bogs. Its small flowers are quite different and appear much more open than the tubular bells of cross-leaved heath and bell heather. The flowers are also arranged up the whole of each stem rather than at the top. They vary in colour from very pale pink to almost purple. Bell heather, meanwhile, is more similar in appearance to cross-leaved heath, but the flowers are always a much deeper purple than the latter’s. They appear in a clump at the top of each stem but are arranged around the whole stem rather than drooping to one side. Bell heather is the least common species on true bogs and tends to prefer drier, well-drained heaths and moors.

Bell heather’s flowers are a dark pinky purple

Crowberry

Another member of the heather family, crowberry forms low, woody mats, sometimes entwined amongst other heather species. The glossy, bright green needle-like leaves have a white stripe on the underside. Tiny pink flowers bloom in April and May but are easy to miss. In late summer, small black berries appear, and these are much easier to see. They provide food for a range of upland species from mountain hares and voles to geese and even occasionally Arctic skuas. The caterpillars of four upland moths feed on the leaves: northern dart, mountain (or Scotch) burnet, black mountain moth and the broad-bordered white underwing. As well as growing in wetter bogs, crowberry grows on cliffs, mountain plateaux such as the Cairngorms and on rockier moors.

Bog Myrtle

This aromatic shrubby plant is another acidic bog specialist. Growing to heights of approximately a metre, it has narrow oval leaves that are similar to those of willow species. In spring, also like most willows, bog myrtles produce catkins. The pale orange male catkins grow on separate plants from the red female flowers. To cope with peat’s low nitrogen levels, bog myrtle forms a partnership with soil-dwelling bacteria living in its root system. These bacteria help it to fix nitrogen from the air, just as they do more famously for members of the pea family such as clovers, vetches and beans. In return, the bacteria get access to some of the plant’s sugars. Oils from the leaves of bog myrtle are used in some insect repellents and it is even supposed to be effective against the dreaded Scottish midge!

Bog Asphodel

This instantly recognisable plant brightens up the landscape in July and August. Its bright yellow, six-petalled flowers grow in spikes, with plants forming quite dense patches in places. As the summer progresses, bright orange fruiting bodies replace the flowers thus continuing to add colour to the bog. Thin, inconspicuous leaves radiate from the base of the plant. Bog asphodel was used in dyes in the past, both for textiles and hair. It was also thought that it caused brittle bones when eaten by livestock. However, while the brittle bones are more likely to be down to the calcium-deficient nature of the habitat, it can be toxic to sheep and cows. Kidney problems, photosensitivity and liver damage have all been recorded but the effects are extremely variable from place to place and within species so there may be another factor at play.

bog asphodel fruiting bodies — The fruiting bodies are a rich rusty orange

Bogbean

Bogbean is another stunner of a plant, with its pink tinged white flowers appearing in bog pools, fens and small lochs from March to June. The flower clusters bloom on the end of 30-centimetre spikes that rise straight up from the water. Each flower sports a frilly, hair-like fringe, with unopened blooms encased in bright pink buds. Bogbean’s leaves are bright green and consist of three oval leaflets branching from a separate stalk to the flowers. In fact, the plant gets its misleading name from these leaves which supposedly look those of broad beans. Although individual plants can be both male and female, to prevent self-pollination they employ the same method as primroses to prevent inbreeding. Each plant will have all of their flowers in either ‘pin’ or ‘thrum’ forms but not both. The way these forms differ affects the way pollen is picked up and deposited by visiting insects and makes self-pollination less likely.

Bogbean flower bog plants — Bogbean flowers are white and pink frilly beauties

Grass-of-Parnassus

This beautiful white flower’s common name supposedly comes from the belief that cows once grazed it on the slopes of Mount Parnassus in Greece. In actual fact, it is not a grass species and doesn’t even look like one. Whatever its etymology, each plant consists of a single flower with five creamy-white petals threaded with green veins. This makes one of its colloquial names, the ‘bog star’, much more fitting. The flowers appear at the top of short stems between June and September. A lover of damp, open places, it grows in bogs, wet pastures, fens and marshes. Sadly, it is no longer as widespread as it once was in the southern part of its range. This is due to extensive drainage of the wetland habitats it favours. Over-grazing by sheep and deer is also a threat, although if no grazing occurs, shrub and tree encroachment can also be a problem.

Tormentil

Although not restricted by any means to wet ground, tormentil is a classic acid soil indicator and so is common across the UK’s bogs. It also grows in acid grassland, heathland and even on verges. It is absent, though, from areas with alkaline soils such as chalk downs. Despite its yellow flowers and deeply toothed, buttercup-like leaves, tormentil is actually a member of the rose family and not a buttercup. Unlike buttercups, and indeed most other roses, tormentil only has four petals rather than five. These petals have a slight notch. Its small, bright yellow flowers appear between May and September. The plant is usually sprawling and low-lying and can form large mats. Traditionally, tormentil has been used in a variety of ways, from herbal remedies for digestive, skin and gum problems to inks and dyes. It also supposedly has anti-inflammatory, antiseptic and antioxidant properties.

Beautiful Bog Plants

At first glance, bog habitats can seem bleak and lifeless places with muted colours dominating for much of the year. However, in summer they come to life with an array of pinks, purples and yellows as its specialist flowers bloom. Added to that is the jaunty bobbing of hundreds of cottongrass heads in the breeze. More importantly, our bogs’ specialist plants are part of an important ecosystem, supporting myriad forms of life from tiny invertebrates to rare birds like the Arctic skua. As vital carbon sinks, they are also crucial in our efforts to halt global warming. As such, we need to appreciate them, and their plants, and protect them like never before.