Since the alphabet acted as a means to memory, like a modern day computer, a massive store of material would have been associated with each of its tree-letters, and the following are just pale hints at vast subjects contained within...
lightness, whiteness, pioneer, betulin, fungi, bark, birch tar, bladder... Cernunnos, wildman of woods, giant, silver wells, handfesting, maypole, bark hats...
rose, light, berries, humus, parasorbic acid, vitamin C, coughs...
doorways, Brigit, protection, earth and heaven, runes, life rod, Dubhros...
beneficial, healer, humus producer, disinfectant Epona, Uffington, Odin, spears, cloud-maker, Imbolc...
animal attraction, tanning, gunpowder, riddles
Bran the Blessed, Manannan MacLir, below the waves, Rough Else
leaning, breaking, flood protection, relations, larder, baskets, miyabeacin, salicin, aspirin
moon, Helice, sacred to poets, witches, wryneck
helping, healer, power over water, making a wish bring in the may, she of the white track, clootie wells, keeper of winds, long sleep, true thomas
long life, strength, insects, lightning, thunder, electrical currents doorman, druid, summer solstice, Janus, oracle, Dodona
shade, evergreen with leaves, strong high quality wood, fevers and colds christian symbolism, Tannus, Gawain and Green Knight, waxing and waning, bull with club foot
human settlements, youth, divination, skin irritations
magic nut, Connla's Well, nine, Bush
Barrow lozenge, caduceus,
salmon of wisdom, Taliesin
rose-like, arching canes, lateral shoots, larvae, basketry, binding, protection leap-frog, Osiris, exhiliration, taboo, Michaelmas
blocking light, decoctions, sinusitis, spleen, wild, toxic, shade, evergreen with leaves, fevers and colds pubs, resurrection, ivy girl, christian symbolism, Tannus, Gawain and Green Knight, waxing and waning, bull with club foot
water-elder, sterile flowers, translucent, cramp bark, swollen glands Samhain, Ukranian beauty, ngetal or reed
Ailm/ Pine
survivor, pioneer, light-seeker, breathing aid, incense, insect home, fibonacci curve, third eye, eye of horus, dancing
thyrsus
Onn/ Gorse
spiky, exploding, fretted webs, uncertainty, nitrogen-fixer, eithne, travelling, kissing season, beltane, overcome
adversity
Ur/ Heather
heathland, adorn, homestead, thatch, brooms, heather ale, heathen, flame of passion, Malvina, charm, good luck
Eadha/ aspen
suckers, attracts fungi, trembler, remedy for fear, underworld journey, shield defence, gives confidence, shifts
perception, accursed by righteous