# The Black Spot – Pirate Maths Outdoors

30 October 2012 · 4 comments

One of the most memorable parts of the story, Treasure Island by Robert Louis Stevenson, is when Billy Bones is presented with a black spot. One side is black, the other side bears a message. A pirate – particularly a Captain – who receives this in their hand will be deposed or possibly even killed outright.

For landlubbing classes or groups of children, looking for black spots can be a nice link. Sycamore trees often get a fungal infection on their leaves, known as Tar Spot Fungus (Rhytisma acerinum). This is easy to spot and a good topic of conversation. It is also ideal for a few simple impromptu maths activities.

For example, each child needs to find a leaf with the black spot. See if children can line up in order of the number of spots found on their leaf. If there are any missing numbers, is it possible to fill these with additional leaves?

This was my black spot order from 1-9
To help children recognise quantities and their associated numeral you can have cards ready for matching. You can also have fun creating leaf sums too. I used the stems for the plus and equal signs.

Pairs or snap can also be played. This is more challenging in that the spots are more randomly set out in a leaf than on a traditional playing card!

There are 2 spots on both these leaves, so they make a pair even though they look quite different

Here are 4-spot leaves. Can you spot the spots?
Number bonds or complimentary addition can be practised by covering up some of the spots. Children can work in pairs, taking turns to cover up some of the spots on a leaf. For example if there is a 7 spotted leaf…how many spots have been covered up?

This leaf has 7 spots

3 spots have been covered by the yellow maple leaf + 4 which are uncovered
This is also a useful way of introducing fractions. If we have 7 spots, then 3/7ths are covered and 4/7ths are uncovered.

The beauty of using sycamore or maple leaves for this purpose is the abundant quantities of available leaves, for free, to those up for finding them and collecting them in a sustainable manner. They are widespread throughout the UK. I bet you can think of lots of other ways of using black spots on leaves now! I want find a black marker pen to make interesting dot-to-dot shapes…

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Katrina Vernon September 23, 2017 at 20:37

This year I was invited to support my friend Anna Canning to record an air quality survey on the canal. We were required to record the Tar spots on the Sycamore Trees, measure their age, in order to establish the air quality along the Edinburgh canal. The Tar Fungi is a bio- indicator.