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Old Irish sail is willow or sallow, and it is one of the letter-names that needs no defending. The kennings are precise and, for once, seasonal. Morainn mac Moín gives lí ambi, "hue of the lifeless" — the grey-white pallor of sallow bark and the underside of the leaf. Mac ind Óc gives lúth bech, "sustenance of bees". Cú Chulainn gives tosach mela, "beginning of honey". Two of the three are about the same observed fact: sallow catkins are the first substantial pollen and nectar of the year, and the hives work them before anything else is out. Whoever composed those kennings kept bees, or knew someone who did.

Bretha Comaithchesa ranks sail among the aithig fedo, the commoners of the wood. Its value was in the rods rather than the trunk. Withies coppiced from willow made creels, baskets, fish traps, hurdles, beehive skeps, and — with hazel — the frames of the hide-covered boats that became the currach.

Willow grows where water is, which puts it at holy wells by geography before anyone makes anything of it. Rag-trees and rod offerings at wells in Ireland and Scotland are usually hawthorn or ash, but willow appears among them, and willow rods were cut for the rounds at some sites. In Ireland and across Britain, sallow branches in catkin stood in for palm on Palm Sunday, since no palm grows — a Christian survival of the ordinary kind, where a local tree takes the liturgical part.

The willow as the tree of grief is English and early modern, not Celtic: the forsaken lover wearing the willow comes out of Tudor ballad and the willow song in Othello. Its lunar and witch associations are later again. Graves made Saille the moon's month and pulled Hecate in from Greek material to preside over it; the modern Celtic-astrology books inherited that whole apparatus. No Irish or Welsh source connects the willow with the moon.

What modern druidry does with Saille — intuition, dreams, water, the receptive month between the equinox and Beltaine — follows Graves closely, and follows nothing older. The practice is coherent on its own terms. It just is not medieval.

Date	Event	Why it matters here
c. 4th–6th c. CE	Ogham inscriptions; S is four scores right of the arris	The letter is ancient
7th–8th c.	Bretha Comaithchesa ranks sail among the aithig fedo	Willow's real legal standing — valued for rods
c. 600–900	Bríatharogam: lí ambi, lúth bech, tosach mela	Pale bark and the first honey of the year
c. 1390	Book of Ballymote copies the Ogam Tract	Saille's willow gloss is one of the secure ones
Medieval onward	Sallow catkins used as palm on Palm Sunday in Ireland and Britain	A Christian custom shaped by which trees actually grow
c. 1600	The willow song in Othello fixes willow as the tree of grief	An English literary association, later read back as Celtic
1948	Graves, The White Goddess	Willow assigned 15 April – 12 May, and given to the moon
1988	Murray and Murray, The Celtic Tree Oracle	Saille becomes a divination card of intuition
1991	McManus, A Guide to Ogam	Confirms sail as a genuine tree-name
1995	Paterson, The Handbook of Celtic Astrology	The willow sun sign, with a personality reading attached

The willow month contains Bealtaine, 1 May, seventeen days in — the second Gaelic quarter day, the opening of summer, when cattle went to the hill pasture and were driven between two fires. That is a genuine festival inside this span, and the span does not begin with it. Graves's boundary at 15 April is twenty-eight days after Alder, nothing more.

The bees, meanwhile, were done with the willow weeks before the willow month opened. Sallow flowers in March. By mid-April the catkins are shedding and the tosach mela the kenning describes has already happened — inside Alder's span, and the tail of Ash's. A calendar built by watching trees would not have placed it here.

• Celtic Tree Calendar — the system, and the year it was invented.
• Alder — the month before.
• Hawthorn — the month after.
• World Zodiacs — the other six systems in the celestial row.
• Religion — the wider religion section.
• Calendar — the live month grid.