Well, Mike - yes, you're on the right trail!
And incidentally, ritual 'code' is what the Celtic 'Mysteries' is all about.
One had to become an initiate by long arduous training - by nature observation
and by pondering the encoded verses of the bards, etc. So, don't judge by
overt appearances in these old verses!
The Ogham and Koelbren Magical Calendar has been partially (at least) restored
by scholars/shaman (remember Robert Graves' _White Goddess_???) some of whom
conflict with one another on issues. Graves gets a serious thumbs down by
Kaleddon Naddair for his efforts. Naddair lists gorse, broom as being at the
station(between Autumn Equinox and Samhain) OHN, along with the 'spindle tree'
- and together with such birds as the shag/cormorant, corncrake, heron, osprey.
The long legged heron was also 'Gwyddnau Garanhir', and Gartan was the Goddess
of Corncrake.(See Kaledon Naddair, _Keltic Bird Lore and Shamanism_, Keltia
You might want to check his ideas and to compare them with others who are
interested in the inner teachings of the Mystery Schools.