Hello, have you got shade and damp conditions? also what state/age/type are the trees themselves in? So can we have a bit more info?

No I am on the Norfolk&Suffolk Border out in the open

The garden is about ten years old from Apple trees to magnolia a large variety of shrubs

On trees not always a problem? not so sure about your shrubs though, have you got some pics as that would be helpful to help identify problems? I meant to say welcome to GOY you live in a nice county

personaly I would welcom lichen, not only dose it do no harm and can be attractive,but it reduce's atmospheric carbon dioxide, so that is a verry healthy spot to be, and have you noticed the cold did not bother it ,it grows from deserts to ice fields, no problem.

I am with Cliffo, if you have lichen on your trees then you are very fortunate. It shows that the air is not polluted and very clean. It does the trees no harm and can look very effective.

I didn't know that Bulbaholic .... lots of lichen on trees here too.
I'd always presumed it an unhealthy thing, how wrong i was.

~ we have lots of lichen too~ it grows all over the place even on the golf course on top of the cliffs amongst the heather and I was always told that it was a sign of good clean air~used to dry it and use as bushes etc on our train layout!

Lichens are plant-like organisms that form when a fungus and algae develop together. They have been known as clean air indicators since the last century when acid rain caused lichens to disappear in our towns, cities and beyond. Now they are returning and can be found all year round in urban areas and the countryside, and on a variety of surfaces from tree bark to park benches and pavements. Recent research has identified that some lichens thrive on air pollution whilst others are highly sensitive to it. This means they can be used to indicate what air quality is like today.

So - don't worry, be pleased! :-)))

He said he was having trouble with lichen, so has his question been answered?

lichen is a brilliant sign of how good the air quality is. lets hope you get lots of interesting species. There are some absolutely beautiful ones.

I agree with everyone else, lichen is a goody. Clean air.

your answers raise a question in my minde,which comes first the clean air or the lichen, Mucky said that the lichen was geting worse, is this because the air is geting clearer so that more lichen can grow,or is there a need for more lichen to clean the air,and it certainly not a chicken and egg question.

Mucky~ if you need advice and can send/take samples get in touch with OPAL ~
About OPAL

The Open Air Laboratories (OPAL) network is an exciting new initiative that is open to anyone with an interest in nature.

We aim to create and inspire a new generation of nature-lovers by getting people to explore, study, enjoy and protect their local environment. In 2007 OPAL received a grant of £11.75million from the Big Lottery Fund.

OPAL is launching a national air quality survey in September 2009 which anyone can take part in. By looking at lichens and counting tar spots on sycamore leaves, you can help scientists understand more about air quality all over England. You can order a survey pack by emailing the OPAL Air Centre or you can download it from the OPAL website from September 2009.
Their website below~
www.opalexplorenature.org and another which may be useful
British Lichens
A site devoted to British lichens and containing photographs to help with identification... Camouflaged caterpillar. ...
www.britishlichens.co.uk/

Upcoming events in your area?
Feb 13 Lichens and air quality day
Bergh Apton Village Hall, Norfolk10:00 - 13:00

OPAL East of England is led by the University of Hertfordshire
East of England partners: British Bryological Society, British Lichen Society, British Mycological Society, Bergh Apton Conservation Trust.

This is taken from a US site~ UBC BOTANICAL GARDEN FORUMS
I am surprised no one has mentioned that Lime Sulphur sets back Lichen's and Moss. Annual treatments of Lime Sulphur keep these to low minimum on your trees.

but another post seems to be more concerned about the impact of a heavy occurrence.~

Harmful thick lichen growth on ornamental trees is an under recognized problem, I believe.
Like many gardeners, I have been stubborn in trying to grow plants not native to their environment in order to achieve a certain effect. Around the circular driveway in front of my house, I planted multiple Kwanzan and weeping cherries, Thundercloud plums, Korean dogwoods, and crabapples. All acquired varying coats of lichens over not only their trunks, but right out onto the very tips of every branch. I lost many of these trees, but was reassured by my landscaper, nurseryman, and web searches that lichens are "harmless".
What I observed was that prior to losing a tree, often some of the bark of the trunk or a branch would become denuded. Fingertip pressure of the soggy succulent lichen growth on dead or dying branches resulted in removal of bark. On healthier parts of the tree, the lichen could be easily removed with gentle scraping, but the bark under the lichen growth appeared moist.
Now I am sure the lichen was at least a bellwether that I had to decrease my almost daily sprinkler system use during summer in a misguided effort to keep my lawn and garden green.
But even greatly reducing the sprinkler system use did not prevent lichen regrowth in soggy spring, fall, and winter weather, after an initial gently scraping off of the lichen growth. I found that I had to gently scrape the most heavily infested lichen growth periodically and began to spray chlorthalonil after the scraping to reduce regrowth (It appears the most commonly recommended agent is copper sulfate).
With this regimen, for the last two years my trees seem to have thrived. I have been rewarded with a fireworks display of flowering trees in the spring, and various shades and shapes of foliage all summer long!
Does this prove the lichen itself was "harmful" to the trees?
Of course not. But the lichen growth was the "canary in the birdcage" that alerted me to change the watering. And I do believe that the constant moist micro-environment under the lichens on the bark surface of these relatively delicate, slow growing trees led to their decline and demise. I don't know whether it was the moisture alone that affected the bark, whether the moisture augmented growth of a more virulent fungus, or whether lichens release metabolic products that can harm bark, or do so through their rhizines. (The late Dr. Shigo in an article that playfully states, "There are no data that shows lichens cause tree or rock diseases." nontheless goes on to say, "The root-like organs of lichens are called rhizines. The rhizines penetrate rocks and aid decomposition. Lichens also produce acids and other chemicals that break down rocks and other materials.". And in the same article:" "Most cyanobacteria fix nitrogen, which means they have an enzyme system that converts atmospheric nitrogen to ammonia and ammonium ions." http://www.treedictionary.com/DICT20...o/LICHENS.html)
Visiting various local area nurseries (even Home Depot!) I am struck by the dramatic increase in ornamental trees being sold that are not really native to this area. And the use of automatic sprinkler systems in my area has seemingly become a "necessity". Thus, I am sure my problem with lichen overgrowth must be becoming more common. Nonetheless, it still seems the most common opinionith regard to lichens is to ignore it because "lichens do not harm trees".

Maybe more light and air circulation necessary?~ this last word from the RHS

Non-chemical control

If algae, lichens and moss are considered unsightly, they can be controlled to some extent by improving air circulation; prune out overcrowded branches and cut back overhanging vegetation. Following this, try to stimulate new growth by feeding, mulching, watering and applying a foliar feed. Once an affected plant regains vigour, badly affected shoots can be pruned out. Control is not necessary on tree trunks.
Chemical control

There are no chemical controls for algae, lichens and moss on plants.

best of luck if it is really becoming a problem!
Arlene

you surprise me Arlene' it is good to know, I was under the impresion that the only intrest to scientists was lichenometry.

I was more than a bit surprised and pleased when I came across the Opal site Cliffo~didn't realise all this was going on! ~their site is full of info and it seems that whilst it appears it is being led by Imperial College london there are Universities all over the UK taking part and involving local people including school children.
It's not just lichen but birds,wildlife etc such as beetles and moths~the West Midland area are running a 5 week free course in Moth identification~ well worth having a look on the site!

Daft I know but have you read the John Wyndam novel 'the trouble with lichens'.....

~ read them all Pam,the Kraken wakes,The day of the Triffids etc but some time ago ~ will have to dig it out!
Pleased to have been of help Mucky!