Mistletoe is important for many insects too. Their early-blooming flowers are important nectar sources for bees and other pollinators when not much else is available, and many insects only live on mistletoe foliage. Three butterfly species in the US are mistletoe obligates (meaning their caterpillars can only feed on mistletoes), but only one, the great purple hairstreak (Atlides halesus) is found in the Chesapeake Bay Watershed.
American mistletoes rarely kill their host tree; their life history strategy is to remain with the host and produce berries as long as possible, so they need their host to survive.
Like many of our traditions, appreciation for (and yes, kissing under) mistletoe developed and evolved as societies rose and fell. European mistletoe (of the genus Viscum) closely resembles leafy American mistletoe, so European colonists and subsequent immigrants easily transferred their customs over to North America.
As Christianity swept through Europe the old traditions became muddled, but mistletoe remained an important winter symbol. It was often hung in doorways to deter demons and witches, and was widely thought of as a universal healer. The custom of kissing beneath it may have come from the belief that it stimulated fertility, or perhaps from an ancient Norse myth that resonated through the centuries. In the story, the beloved son of Frigg, the goddess of love and beauty, was killed by an arrow made from mistletoe. The gods all agreed that the plant should never hurt anyone again, but rather be dedicated to happiness and usefulness. Frigg’s tears became the white berries of mistletoe, and the goddess swore that she would kiss anyone who walked beneath it.
No matter what the origin of the kissing custom is, American mistletoe makes a lovely winter decoration. Rather than an excuse to smooch, it’s a great opportunity to talk to guests about forest ecology and the fascinating biology and cultural history of this strange little parasite. Look up into the empty branches of oaks and sweetgums for a cheery clump of mistletoe this winter. It will likely be too high up to reach, but that’s a good thing; mistletoe is a valuable member of our forests and will do a lot of good up there in the treetops.
Above information is excerpted from:
https://www.allianceforthebay.org/2017/12/mistletoe-a-merry-parasite/