It started long ago
Much of the roundhouse and crannog building structure is a clue to tree lore since the right timber for the correct purpose is essential knowledge. (more to come here on this yet below is something of the construction stages).
Eighteen trees, indigenous since the retreat of the last Ice Age, belong to an ancient tree lore that understood trees from a different perspective to ours. 3,500 years ago, throughout western Britain and much of Europe, an oral tree lore sometimes known as the Tree Alphabet was likely in use.
Whilst not an alphabet as we might understand it (it was deliberately a spoken and not a written language), it had eighteen tree-letters, each letter represented by a different tree, each of which referenced specific botanical, mathematical, musical, poetical, mythological, geodetic and astronomical properties. Although the oral Celtic tradition died out under Roman influence, clues to its purpose remain.
Stone calendar months
In many stone circles, such as Callanish (Calanais) and the recumbent variety of the North East, a calendrical system of stone placement corresponds surprisingly well to the month structure of the tree-letters. In particular, the Celtic year contained not twelve, but thirteen months, being based on a lunar cycle, with each month having the same period of twenty-eight days and each referencing a consonant of the Alphabet. The year starts with ‘B’ and progresses ‘sun-wise’ (clockwise) in three sections to end with ‘R’.
The five vowels of the alphabet, each also represented by a tree, form not a period (like the months), but a point of the year. The two end points ‘A’ and ‘I’ belong at the winter solstice, effectively forming the ‘beginning and end’ of the cycle, with ‘U’ at the summer solstice, ‘O’ at the spring equinox and ‘E’ at the autumnal equinox. The Celtic year, with a total of 364 days, required an extra ‘adjustment’ day to complete its cycle (which day is possibly the ‘and a day’ frequently found in folklore). This missing day also corresponds to its ‘eighteen plus one’ tree-letter lore, the significance of which hints at the underlying weave of metaphor in the druidic tradition, where nineteen has considerable significance as does the 18.6 years in which lunar and solar calendars synchronise in a ‘lunar standstill’. The four feast days of Samhain, Imbolc, Beltaine and Lughnasa are similarly points orientated to the four seasonal points of change. Very much more on this to be found in the White Goddess.
At a time when written documents were of little use, the Tree Alphabet had a purpose not dissimilar to the web of today, in having vital mnemonic ability to make connections and assign a wide range of information in a form that could be committed to memory by an understanding of the yearly cycles and properties of trees.