close X

We’re ready for you

We’re looking forward to welcoming you back to our museums.  We may look a little different, but we still feel the same.  We’re starting to reopen our museums beginning with the Ulster Museum on 30 July.

ULSTER MUSEUM
BOOK TICKETS NOW

ULSTER FOLK MUSEUM
BOOK TICKETS NOW

ULSTER TRANSPORT MUSEUM
BOOK TICKETS NOW

ULSTER AMERICAN FOLK PARK
BOOK TICKETS NOW

Town and Country Lichens

Exit Menu

Come on a hunt around the Folk Museum for some of the strangest living things on Earth. They cover many rocks and trees with multi-coloured mosaics, and give a sense of age to walls and buildings, yet we barely notice them. They are lichens.

More than 1200 different species of lichen are found in Ireland. Most of them are known only by their scientific names. You can find out more about these on the Lichen Ireland website but we will look at just a few of those that are easy to spot.

What is a lichen?

What is a lichen?

Read more
Ancient milestone

Ancient milestone

Read more
Rusty rocks

Rusty rocks

Read more
 Splashes of yellow

Splashes of yellow

Read more
Orange spots on an Orange Hall

Orange spots on an Orange Hall

Read more
Lichens, or paint spots?

Lichens, or paint spots?

Read more
Churches and graveyards

Churches and graveyards

Read more
Patchwork lichens

Patchwork lichens

Read more

What is a lichen?

Lichens are a remarkable partnership between two completely different kinds of organism – an alga (a single-celled type of plant) and a fungus. Together they can live in places that are impossible for many other living things. The fungal partner attaches to the rocks or tree bark and it protects the algal cells that live within it, These algal cells produce sugar through photosynthesis, some of which goes to the fungal ‘landlord’ in payment.

Image: Physcia tenella © Mike Simms
Physcia tenella © Mike Simms

What we see of a lichen is mainly the fungal partner; the algal cells are buried within it. Some lichens disperse by fungal spores from small discs on the lichen surface; these must combine with algal cells to form a new lichen. Others have powdery patches, formed of a mix of algal and fungal cells, which can be blown by the wind or carried by animals.

The lichen above is Physcia tenella, which does both.

Newly built stone wall
Newly built stone wall
Old stone wall
Old stone wall

Newly built stone walls, without any lichens, have a harsh appearance compared with those covered with many years of lichen growth. Decades of weathering and lichen growth ‘softens’ the appearance of old stone walls.

Image: The trunks and branches of many trees are encrusted with lichens.
The trunks and branches of many trees are encrusted with lichens.

Ancient milestone

An ancient lichen-encrusted milestone ©
Mike Simms
An ancient lichen-encrusted milestone © Mike Simms
Smooth white patches covered with thousands of tiny dark pits are characteristic of Verrucaria baldensis, a lichen that grows on limestone.
© Mike Simms
Smooth white patches covered with thousands of tiny dark pits are characteristic of Verrucaria baldensis, a lichen that grows on limestone. © Mike Simms

Look out for the milestone just up the hill from Coalisland Spade Mill. It is made of limestone and is covered with crusts of several different species of lichen. You would barely notice them but it is these lichens that impart a sense of age to the milestone.

Look on the top and you will see irregular white patches with many tiny white dots. These are actually little pits that the lichen Verrucaria baldensis has excavated in the limestone.

Rusty rocks

The true colour of the basalt boulders that make up this field wall are almost entirely obscured by crustose lichens.© Mike Simms
The true colour of the basalt boulders that make up this field wall are almost entirely obscured by crustose lichens.© Mike Simms
Rusty patches of Porpidia crustulata on a basalt boulder.
© Mike Simms
Rusty patches of Porpidia crustulata on a basalt boulder. © Mike Simms

Take a look at the rough stone wall on the road between Coshkib Hill Farm and Coalisland Spade Mill. Some of the rocks, particularly the big boulder by the field gate, have rusty looking patches with small black discs scattered across them. This is Porpidia crustulata, a lichen that extracts iron from the rock to give it this rusty orange colour.

There are plenty of other crustose lichens on these rocks, in shades of grey, brown and yellow. See how many different types you can spot.

Splashes of yellow

Was Lisrace Forge once painted yellow, or is there a more natural explanation?
© Mike Simms
Was Lisrace Forge once painted yellow, or is there a more natural explanation? © Mike Simms
Patches of Psilolechia lucida, masquerading as splashes of yellow paint, on the walls of Lisrace Forge. The grey patches on the left are another lichen, Porpidia tuberculosa. © Mike Simms
Patches of Psilolechia lucida, masquerading as splashes of yellow paint, on the walls of Lisrace Forge. The grey patches on the left are another lichen, Porpidia tuberculosa. © Mike Simms

On the stone and brickwork around the doorway of Lisrace Forge are yellow patches that might easily be mistaken for the remnants of an old coat of paint. They are actually a thin crusty lichen called Psilolechia lucida. It is a common lichen on sandstone and brick that is slightly sheltered from the rain.

Orange spots on an Orange Hall

Hand and Pen Orange Hall. Not much growing on this building, or is there?
Hand and Pen Orange Hall. Not much growing on this building, or is there?
The weathered concrete lintels on these walls are home for several common species of lichen, but they are quite well hidden unless you know what to look for. © Mike Simms
The weathered concrete lintels on these walls are home for several common species of lichen, but they are quite well hidden unless you know what to look for. © Mike Simms

Look along the top of the walls outside the Orange Hall to find little clusters of irregular orange spots on a faint grey-green patch a few cm across. This is Protoblastenia rupestris, one of the most common and characteristic lichens growing on concrete.

Image: Protoblastenia rupestris is one of the most common lichens on concrete. The orange spots on a grey-green background are particularly distinctive © Mike Simms
Protoblastenia rupestris is one of the most common lichens on concrete. The orange spots on a grey-green background are particularly distinctive © Mike Simms

Lichens, or paint spots?

A sandstone window sill by the sweet shop. Home for a few hardy lichens.
© Mike Simms
A sandstone window sill by the sweet shop. Home for a few hardy lichens. © Mike Simms
Various coloured splodges on the window sill. Some are lichens. Some are not.
© Mike Simms
Various coloured splodges on the window sill. Some are lichens. Some are not. © Mike Simms

Look for coloured patches on the windowsills of the houses either side of the sweet shop, on the corner of Tea Lane. Most of them are lichens, although one or two are splashes of paint!

Small circular grey patches with concentric rings of black spots are Rhizocarpon petraeum, a common lichen on sandstone.

The dirty yellow patches are lichens too and, if you look closely, you will see small yellow discs scattered across them. This yellow lichen is Candelariella aurella, another common lichen on sandstone.

 

Grey circles with rings of black spots make Rhizocarpon petraeum easy to identify
Grey circles with rings of black spots make Rhizocarpon petraeum easy to identify
Dirty yellow patches, with small yellow discs, of Candelariella aurella on the window sill by the sweet shop. © Mike Simms
Dirty yellow patches, with small yellow discs, of Candelariella aurella on the window sill by the sweet shop. © Mike Simms

Quite often the small discs on lichens look like tiny wine gums or jam tarts. Drop into the sweet shop and check out their wine gums.

Churches and graveyards

Only a few lichens grown on the headstones in this churchyard, but there a few species of lichen hiding on the building itself. © Mike Simms
Only a few lichens grown on the headstones in this churchyard, but there a few species of lichen hiding on the building itself. © Mike Simms
The rough mortar on the church walls is the ideal place for certain lichens to grow. © Mike Simms
The rough mortar on the church walls is the ideal place for certain lichens to grow. © Mike Simms

The exterior walls of the church in the town area are covered in mortar mixed with broken sea-shells. This rough, lime-rich surface is the perfect home for several different species of lichen. Two of these are particularly easy to find on the front of the building, to either side of the door. One of these is white, from which it gets its name of Lecanora albescens.

The other is orange and its name too comes from the colour; in this instance it is called Caloplaca citrina (think oranges and lemons).

Churches, and particularly graveyards with their diversity of different rock types, are often an important habitat for lichens.

Lecanora albescens are common on limestone, concrete and mortar © Mike Simms
Lecanora albescens are common on limestone, concrete and mortar © Mike Simms
The powdery crust and darker orange discs of Caloplaca citrina are common in sheltered crevices on concrete and mortar. © Mike Simms
The powdery crust and darker orange discs of Caloplaca citrina are common in sheltered crevices on concrete and mortar. © Mike Simms

Patchwork lichens

Hundreds of different species of lichen grow on the trunks and branches of trees, often forming a patchwork of tightly attached crusts and leafy clumps of various colours. Many of the larger trees around the Folk Museum have only a poor cover of lichens, probably because they suffered from decades of air pollution blown from the coal fires of Belfast.

The best place to see some of these lichens up close is on the trunks of the young trees on the green opposite Tea Lane.

Image: The diversity of different lichens on trees may form multicoloured mosaics on their trunks. There are at least four different species in the picture above. Can you tell them apart?
The diversity of different lichens on trees may form multicoloured mosaics on their trunks. There are at least four different species in the picture above. Can you tell them apart?
Look for green patches with black borders and small black discs.This is Lecidella elaeochroma, one of the most easily recognised crustose lichens on smooth tree trunks. © Mike Simms
Look for green patches with black borders and small black discs.This is Lecidella elaeochroma, one of the most easily recognised crustose lichens on smooth tree trunks. © Mike Simms
Among the most common of lichens found on smooth tree bark is Lecanora chlarotera, which forms white patches with small brown discs. The yellowish lichen in this picture is Lecanora symmicta, another common related species.© Mike Simms
Among the most common of lichens found on smooth tree bark is Lecanora chlarotera, which forms white patches with small brown discs. The yellowish lichen in this picture is Lecanora symmicta, another common related species.© Mike Simms
Image: Some lichens, such as this Parmelia sulcata, have a leafy rather than a crusty appearance.© Mike Simms
Some lichens, such as this Parmelia sulcata, have a leafy rather than a crusty appearance.© Mike Simms