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From Coal to Carnations

From Coal to Carnations: The Evolution of Plants featuring fossils from the Brymbo Fossil Forest

This page contains interpretation from the exhibition that you can download in various formats.

The information is for private research and study. It is not for commercial publication. Copyright is shared between the Grosvenor Museum, Chester & Wrexham Heritage Services.

Floral Forward

Introduction to Plant Life

Plants are the key to life on Earth. They photosynthesise to produce oxygen, which led over many millions of years to the Earth’s breathable atmosphere. The Plant Kingdom is split into two main groups – flowering plants (or Angiosperms) and non-flowering plants. There are approximately 400,000 recorded living species, of which about 300,000 species are flowering plants.

The oldest evidence of fossil plants are cyanobacteria, which are common in modern stromatolites, and are dated at approximately 3.2 billion years old (3,200,000,000 years old). Examples this old are rare, and only a handful have been found. There are also structures in 3.46 billion year old Australian rocks that may be from plants. The earliest land life may have been microbial and algal, and terrestrial environments may have been populated by soil-forming microbes before the ancestors of modern plants moved onto land.

Geological time can be split into three plant ages. The oldest of these was the Palaeophytic (approx. 450–250 million years ago), which was dominated by ferns and club-mosses. It was during the Palaeophytic Period that the Coal Measures of the Carboniferous were deposited. The Mesophytic (approx. 250–100 million years ago) was the age of the conifer, along with cycad-like forms and gingkos. The Cenophytic (approx. 100 million years ago to present) is the modern world of flowering plants.

Creating Coal

Carboniferous Plants

During the Carboniferous Period (359–299 million years ago), Britain was a few degrees north of the equator with a wet-tropical, possibly monsoonal, climate. The Coal Measures, the source of most British coal, were laid down during this time.

The British Coal Measures are mainly alluvial sediments deposited on an elongate, forest-covered, delta-plain that extended as far as Poland. The trees of the floodbasin swamps produced vast amounts of plant litter. This led to the formation of peat, which over millions of years changed into coal. When the rivers that travelled through the floodplain swamps became flooded, the area turned into a lake destroying the forest that grew there.

There was a wide diversity of plants in the Carboniferous Period, with six major groups.

Lycopsids. These were the largest plants alive in the Carboniferous, and included Lepidodendron. (From Plant Fossils of the British Coal Measures. Palaeontological Association Field Guide to Fossils No. 6.)

Calamites. These were similar to modern horsetails, except they were much larger. (From Plant Fossils of the British Coal Measures. Palaeontological Association Field Guide to Fossils No. 6.)

Sphenophylls. These were probably related to calamite horsetails but were much smaller and probably formed low-lying, scrambling vegetation on parts of the river banks. (From Plant Fossils of the British Coal Measures. Palaeontological Association Field Guide to Fossils No. 6.)

Ferns. These varied in size from small, scrambling plants, to tree-ferns. (From Plant Fossils of the British Coal Measures. Palaeontological Association Field Guide to Fossils No. 6.)

Pteridosperms. These varied from small trees to scrambling creepers. (From Plant Fossils of the British Coal Measures. Palaeontological Association Field Guide to Fossils No. 6.)

Cordaites. These were mainly trees up to 30m high, though smaller forms are recorded. They occupied a range of habitats including flood-basins, sea coasts and uplands. They were primitive relatives of the conifers. (From Plant Fossils of the British Coal Measures. Palaeontological Association Field Guide to Fossils No. 6.)

Petrified Plants

The Fossil Forest at Brymbo

In 2003, fossil plants were discovered at the site of Brymbo steelworks. Initially six tree-sized plants were discovered in a small area. Work since then has revealed over 20 specimens. Parkhill Estates, developers of the Brymbo site, quickly realised the significance of this discovery and now hope to develop the area into an education centre and tourist attraction.

Fossil plants are very rarely preserved where they grew and most have become fragmentary and detached from the plant and then drifted away by wind or water. This means that although the more durable parts, for example wood, had less chance of being eaten or decaying, it is the lighter and less rigid parts (leaves, fruits, seeds) that are the most commonly found fossils.

When trees are killed en masse and are rapidly buried in sediment their trunks and other parts become fossilized to preserve a forest in stone. There are few Carboniferous fossil forests known. Brymbo fossil forest is thought to have formed in a big flood and there are structures around the plants that suggest this to scientists.

The fossil forest at Brymbo has a large number of two main types of tree-sized plants – Calamites and Lepidodendron – palaeobotanists (people who look at fossil plants) think that these plants would have lived at different times. There are also many remains of fossilised ferns, which would have lived alongside both the Calamites and Lepidodendron.

Sparks and Steel

The History of Brymbo Steelworks

In 1990 Brymbo Steelworks was closed after almost 200 years of iron and steel making. The last steel melted was on 27th September, when over 1,000 workers lost their jobs. At its peak in the 1970s over 2,500 people were employed at the steelworks.

Mining can be traced back at Brymbo to the 1400s, and the extraction of coal to mediaeval times. In 1792, John Wilkinson purchased 500 acres of estate at Brymbo, in order to access the Coal Measures that lay below. Wilkinson extracted his own coal on site so that it would not affect the price of his iron and reduce his profits.

Wilkinson initially tried lead smelting at Brymbo. In 1796, after the construction of the first blast furnace, which still stands today, Brymbo became a centre for iron production. When he died in 1808, the plant works went through years of turmoil before Henry Robertson was commissioned in 1842 to produce a detailed report on Brymbo. By 1880 he returned to the plant with the idea of a steel plant and the first steel trial was done in December 1883. The Brymbo Steel Company was formed in 1884.

Brymbo became world famous for producing high quality steel that other manufacturers were unable to match. It was this quality of workmanship that allowed this small, isolated steelworks to attract loyal customers from all over Britain and from overseas.

The old steelworks site is currently undergoing re-development, with the objective of bringing industry and life back to the area. The older industrial structures, some of them Scheduled Ancient Monuments, remain a proud monument to Brymbo’s industrial past and the skills of the local steelworkers.

Flourishing Fauna

Post–Carboniferous Plants

At the end of the Permian Period (251 million years ago), the Earth was subjected to the worst extinction of life ever seen.  95% of species in the sea were wiped out, and land vegetation showed a catastrophic collapse at this horizon. Of the gymnosperms (cycads and conifers), there are 19 families described from the Permian, but only three after the extinction event. After this event a new type of vegetation developed that included new ferns and gymnosperms.

During the Jurassic the flora was composed of plants that can be classified in modern families, including the Monkey Puzzle and Redwood families. Cycads were prominent; these bore a superficial resemblance to palm trees with the stout stems and a crown of large, stiff leaves. The Jurassic flora of Yorkshire is famous for its abundance and diversity. This included horsetails, which lived in swampy sediment, that are sometimes found in their growth position. The majority of plants lived in drier conditions; fragments shed were carried away and preserved as fossils. Ferns are common and numerous, and are thought to have been the dominant plants on land.

The oldest evidence of flowering plants is from the Late Jurassic or Early Cretaceous (approx. 145 million years ago). The rise of flowering plants has been spectacular, and they have replaced ferns and gymnosperms as the dominant group in most habitats. Flowering plants are relatively close to gymnosperms, though the split is very ancient.

The Need for Nectar

Flowering Plants

Flowering plants belong to the class Angiospermae, and have their seeds enclosed in an ovary. The class contains the most advanced vascular plants. There are about 300,000 species of flowering plant. In terms of geological time they are comparative newcomers, becoming noticeable during the Cretaceous Period (145–65 million years ago). By the end of the Cretaceous 50–80% of land plants were flowering plants.

Even though leaves, wood, fruits, seeds and pollen are all abundant in the fossil record, flowers are rare as fossils. We see fossils with recognisable affinities to modern families, including the fruits and seeds of the water-lilies (Nymphaeaceae), and magnolias (Magnolialies), by 127 million years ago.

By 93 million years ago, there is evidence of plants that are related to Witch Hazels (Hamamelidaceae) and the Saxifrages (Saxifragales). Around the same time, there is the first evidence of birches, alders, beeches, and oaks (Fagales group).

Plants have evolved some very effective ways of spreading seeds: exploding seed pods into the air; flying or floating seeds; hooks that latch onto animals; and berries that pass through animals unharmed to germinate. Plants can also reproduce without seeds, when a plant reproduces a genetically identical plantlet.

Flowering plants are everywhere around us and include grasses and grains as well as what we recognise as flowering plants.

The following may be useful when labelling an illustration of a plant in science classes.

Labels for plant diagram

Pollen grains are produced on the stamen.
As the petals grown, they open to reveal the male and female parts of the flower.
The flower bud is covered with protective sepals.
As seeds develop petals die and drop off.
Leaves take in CO2 to make sugars.
Vascular tissues carry food and water through the plant.
The main root divided to anchor the plant in the ground.
Fine root hairs near the tip of each rootlet absorb water and minerals from the soil.
Root growth occurs at the tip of each root.
Side roots grow out from main root.
Leaves have a network of parallel or branching veins.
Petals are often colourful and attractive.

Just a Pretty Picture?

Botanical Illustration

For over 450 years botanical illustrators have been drawing and colouring plants. The Grosvenor Museum, Chester, has an extensive collection of published illustrations from the 18th century onwards, including those in Curtis’ Botanical Magazine and Flora Danica.

Although attractive to look at, the main goal of botanical illustration is scientific accuracy. It is a difficult art to perfect as it requires both accuracy and artistry to convey the individuality of the species. It involves careful measuring of specimens so that they are accurate enough to be able to distinguish between different species.

Dr Harold Drinkwater

Dr Harold Drinkwater was born in Northwich, Cheshire in 1855 and trained to be a doctor. Part of his medical training was the study of botany, which prompted an interest in the British flora. He practised medicine first in Sunderland and then moved to Wrexham in 1890.

His pictures were normally on green paper, in order to show the plants against their usual environment. The pictures were drawn from specimens soon after they were collected. The plants were usually collected from the area around Wrexham, and most depict wild plants in hedgerows and woodlands of Wales.

He would draw the plants in pencil before adding colour with gouache (watercolour mixed with Chinese white). On some pictures he also put a black outline. Occasionally he added shadows to produce a three-dimensional effect.

His paintings were exhibited at the National Eisteddfod in Wrexham in 1912. There are 103 of his paintings in the collections of the Grosvenor Museum and a further 385 at the National Museum of Wales, Cardiff.

Pressing for Posterity


A collection of preserved plant material is called a herbarium. This may include whole plants or plant parts, which are usually mounted on a sheet in a dried form.

Herbaria are essential for the study of plant taxonomy (naming), stabilising of these names (to ensure that the same species is always called the same name), and the study of geographical and historical distributions. Plant specimens that were collected in the past and preserved in herbaria can be compared to specimens found today and used to track environmental change and human impact.

Most of the Grosvenor Museum’s herbarium was collected about 100 years ago. There are several important individuals’ collections in it. These include that of Eliza Potts and the diatoms of Dr Stolterfoth. The Museum’s herbarium has recently been returned from long-term loan and is currently being digitised and packed in materials suitable for long-term storage.

Eliza Potts came from a well-known Chester legal family. She collected many specimens from close to the family estate at Moel Fammau, near Loggerheads, and from Lancashire where she spent several summers, as well as across Cheshire and North Wales. These areas are well represented in her herbarium.

Herbarium specimens are laid out to maximise the information held by the plant. The have a label that has information such as species, collector and locality on them, as well as the museum’s unique number for that specimen.

May be of use as beginner’s guide to how to create your own herbarium

Captions for series of images at bottom

Display both sides of the flowers when possible.

Display both sides of leaves, if necessary by detaching and turning one leaf over.

If only one leaf has been collected, cut off part of it and turn it over, or place it in a paper envelope.

Expose hidden flowers or fruits by removing leaves, which are kept in paper envelopes.

If possible separate clumps of plants without damage, removing soil from roots carefully.

When mounting more than one plant they should all be aligned, with the heaviest specimen at the bottom.


The interpretation for this exhibition was researched and written by Dr Kate Riddington, Keeper of Natural History at the Grosvenor Museum, Chester, with help from Dr Jacqui Malpas, Peter Appleton, Brymbo Heritage Group and colleagues in other museums. The Welsh language version of the exhibition was produced by Wrexham Heritage Service.