Mistletoe
United Kingdom
The parasite plant the druids held sacred, bridging worlds and granting protection.
The May tree's sacred blossom, carried at Beltane for love and gathered for powerful hedgerow magic.
Hawthorn — Crataegus monogyna — is the sacred tree of the Celtic month of May, its white blossoms opening precisely around Beltane (May 1st) and giving the tree its common name 'may tree.' The hawthorn occupies a unique and somewhat paradoxical position in British and Irish folk tradition: simultaneously associated with love, luck, and spring abundance on one hand, and with death, bad luck if brought into the house, and fairy power on the other. This tension between the tree's fecundity-symbolism and its otherworldly associations gives hawthorn blossom a complex and compelling charm quality.
The prohibition against bringing hawthorn blossom indoors is one of the most persistent plant-superstitions in Britain — many people who no longer believe in luck or fairy magic still feel a visceral reluctance to bring the blossom inside. The smell of hawthorn blossom contains trimethylamine, a chemical produced in the early stages of decomposition, which may have contributed to its association with death and otherworldly things — the smell of dying and the smell of regeneration bound together in a single flower.
Despite (or because of) its ambiguity, hawthorn was central to Beltane celebrations. Young people went 'a-maying' — gathering hawthorn blossom in the woods before dawn — an activity that was as much a socially sanctioned excuse for romantic encounters as it was a ritual gathering of sacred plant material. The blossom was woven into wreaths and garlands for Maypoles, worn in the hair, and carried as love tokens. The hawthorn tree itself — particularly lone hawthorns in fields, believed to be fairy trees — was never cut or damaged without risk of supernatural retribution.
Hawthorn blossom represents the fertile, regenerative, boundary-crossing energy of late spring — the moment when winter is entirely defeated and life insists on its own exuberance. It carries the paradox of beauty containing the possibility of danger, of love requiring the courage to enter liminal spaces. It is the charm of those who are willing to go to the edges of the known world in search of what they most desire.
Gather hawthorn blossom outdoors and wear it in your hair or carry it on Beltane (May 1st) for love luck — but respect the tradition of not bringing it inside the house. Dry small amounts of blossom for use in sachets or love magic. Meditate near a flowering hawthorn hedge to access the boundary-crossing energy the tree embodies.
The Holy Thorn of Glastonbury — a hawthorn tree claimed to be descended from Joseph of Arimathea's staff, which he planted upon arriving in Britain — blooms twice a year, once in spring and once in winter around Christmas. A sprig from it is sent to the reigning British monarch each Christmas, a tradition maintained since at least the 17th century. The original tree was vandalised in 2010, but scions (grafted descendants) survive.
The prohibition has multiple explanations: the smell of hawthorn blossom contains trimethylamine (associated with decay), the tree is associated with fairy power and bringing fairy-connected objects inside risks inviting the fairies themselves in, and Christian tradition sometimes associated the crown of thorns (hawthorn) with suffering and death.
The indoor prohibition is primarily British and Irish. In France, hawthorn blossom is generally welcome indoors, and in Germany the tree's thorny protection is valued without the fairy-association ambiguity. The specifically Celtic fairy tradition is what generates the British/Irish hesitation.
Lone hawthorn trees standing in the middle of fields, particularly old ones, were believed to be resting places or gateways for fairy (fairy/spirit) activity. Their isolation and apparent deliberateness — they stood where other trees were cleared, as if protected — suggested they had supernatural patrons. Such trees were never disturbed in traditional Irish and Scottish communities.
United Kingdom
The parasite plant the druids held sacred, bridging worlds and granting protection.

United Kingdom
Scotland's rarest bloom, whose white mutation brings extraordinary fortune to its finder.
France
The lily of the valley given on May Day as France's most beloved luck gift.