The Many Faces of Chichester Cross

Chichester Cross is a slightly mysterious stone construction at the heart of my home town. It has been around for five hundred years or more and has endured its share of sun, wind and rain in that time. The two larger pictures show the effect of just 6 years of exposure.

The elements do not come at it from uniform or random directions though and so it feels the effects in different ways on each side. This leads to different erosion patterns and weathering marks. It also means that lichens find different sides more or less appealing. The smaller pictures show the edges of the eight flying buttresses. No two are the same.

Hawaiian Tropic Moss

There are three words that you are unlikely to see together in the same sentence ever again. What is my excuse here? There is a well-known relationship between sunshine and moss or lichen growth, but there are subtler, more interesting ones as well. I have lost count of the number of people who have confidently told me that moss only grows on the north side of trees and buildings. I have dealt with that partial myth elsewhere, but here I want to explore a rarely-noted trend.

In England and large parts of northern Europe mosses and lichens will often grow on the south side of trees and buildings, but they will nearly always display differences to nearby brethren growing on the north side. The crucial thing to remember is that we are dealing with trends and patterns when observing nature, avoiding rules wherever possible. The navigator who tries to live by the rule that moss only grows on the north side is likely to find themselves lost and bedding down on the stuff before too long.

The two pictures above show roofs on either side of East Street, Chichester. There is lush green moss growing on the north-facing roof, but if you look closely at the second photo you will see a brownish ochre growth running along the top of the south-facing, very sunny, roof tiles. This colour difference is a pattern that is quite consistent and satisfying to spot. The way I like to remember it is the 'Hawaiian Tropic Moss Trick', if you find what looks like normal moss that has has gone south with a bagful of lotion and lain on a bed in the sun for too long then the chances are it is south-facing. Beware though, this works well on buildings, but on trees the colour patterns change again. It will be their turn next week...

Slightly Fickle Moss

Having spent the morning organising images for upcoming courses, I was reminded of a regular problem with learning anything practical from nature. There is a real tendency to bias. By which I mean when we are learning something new there is a great temptation to either make our observations fit our predictions, or to overlook things until we find something that looks the way we want it to.

Moss on trees and buildings is a great example of this. The popular notion is that moss will grow on the north side. This is sometimes true, but often not and for a good reason. The harsh truth is that moss doesn't care where north is at all. Moss will grow where moisture is retained and this is determined by rain, sun, wind and other factors. If it was only about the sun then it would be a far better indicator of north.

To avoid putting too much of a dampener, forgive me, on the spirits of those who like to cling to the north moss theory, here is a nice picture taken near my home looking east at a tree trunk. Lots of moss on the north side, next to none on the south.