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Mistletoe: Why We Kiss Under It and Why Animals Love It

One of the most legendary of holiday traditions is kissing under the mistletoe at Christmas and New Year’s Eve. But why exactly do we do that?

mistletoe berries
The white-berried holiday mistletoe we kiss under at Christmas or New year’s Eve (if we’re lucky) is one of more than 1,300 species of mistletoe. Hanging mistletoe is a Christmas tradition in the U.S., while in Europe, it is more commonly used as a decoration on New Year’s Eve. Photo by Hans.

What is mistletoe?

Mistletoe is a parasitic plant that attaches to the branches of a woody tree or shrub and takes water and food from its host. Unlike other parasitic plants however, mistletoe doesn’t completely depend on its host plant. It performs some photosynthesis on its own and typically doesn’t kill the host plant, but it may stunt its growth.

Why do we kiss under mistletoe?

Pre-Christian cultures regarded the white berries of mistletoe as symbols of male fertility because the seeds resembled… wait for it… semen. Mistletoe played an important role in the Druidic fertility ceremony of Oak and Mistletoe and the Romans associated mistletoe with peace, love, and understanding, and hung it over doorways to protect the household. Mistletoe continued to be associated with fertility and vitality through the Middle Ages, and by the 18th century, it was incorporated into Christmas celebrations.

The tradition of kissing under the mistletoe is credited to servants in Victorian England in the late 18th century. The tradition dictated that a man was allowed to kiss any woman standing underneath mistletoe, and that bad luck would befall any woman who refused the kiss. One variation on the tradition stated that with each kiss a berry was to be plucked from the mistletoe, and the kissing must stop after all the berries had been removed (but never eaten, because they’re poisonous, but usually not fatal).

How to spot mistletoe

Mistletoe has green stems with oval-shaped, thick, evergreen leaves. The rounded plants, roughly 2 feet in diameter, can easily be seen on deciduous trees in winter when the leaves have fallen. Female mistletoe plants produce small, sticky, whitish berries in fall.

Two species of mistletoe are native to the United States: the leafy American mistletoe (the one commonly associated with our kissing customs) and the mostly leafless dwarf mistletoe. American mistletoe is native from New Jersey to Florida and west through Texas; Dwarf mistletoe is mostly found in the western United States and Mexico but some species also occur from central Canada and southeastern Alaska to Honduras and Hispaniola.

In the UK, Mistletoe grows in the branches of Hawthorns, Poplars, Limes, and cultivated Apple trees. It prefers host trees in open habitats with plenty of light and is generally not found in woodland settings. Mistletoe grows throughout England and Wales but is rarely seen in eastern and northern England and Scotland. The variety of mistletoe that’s most familiar, oak mistletoe (Viscum album), produces yellow flowers and white berries. Other varieties produce red or pink berries, but in all varieties, the berries are only found on the female plant.

Related Post:  How to Grow Blackberries

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Mistletoe’s role in the ecosystem

Despite its association with the winter holidays, mistletoe grows year-round and is an important plant, providing essential food, cover, and nesting sites for a wide array of wildlife. In fact, some birds, insects, and butterflies couldn’t live without it.

All mistletoes have one thing in common – they’re parasites which grow on the branches of a wide range of trees and shrubs (American mistletoe’s scientific name, Phoradendron, means “thief of the tree” in Greek). Technically, mistletoes are “hemiparasites” and not true parasites, because most of them have the green leaves necessary for photosynthesis and so are not completely dependent on the host plant.

Berries are only produced by female mistletoe plants – males produce pollen. The berries are small, sticky, and whitish and are a source of food for many birds. The birds feed on and digest the pulp of the berries, then excrete the seeds which stick to any branch on which they land. The sticky seeds of mistletoes may also hitchhike to other host trees on a bird’s beak or feathers or on mammal fur. Or – get this – the seeds of American mistletoe explode from ripe berries, shooting a distance as far as 50 feet(!).

After the mistletoe seed germinates, it sends out roots that penetrate through the tree’s bark and into its water and nutrient-conducting tissues, where rootlike structures called haustoria develop. The haustoria gradually extend up and down within the branch, stealing water and nutrients from the host tree. Initially, the parasitic plant grows slowly and it may take years before the plant blooms and produces seed. Old, mature mistletoe plants may be several feet in diameter, and on some host species, large swollen areas develop on the infected branches where the mistletoe penetrates. Eventually, mistletoe grows into a thick mass of branching, misshapen stems, referred to as “witches brooms”.

dwarf mistletoe in pine tree
A dwarf mistletoe caused this witches’ broom in a pine tree.

Which wildlife species depend on mistletoe?

Mistletoe is slightly toxic to humans, but the high-protein berries and leaves are eaten by many mammals, especially in autumn and winter when other food is scarce. Animals such as elk, cattle, deer, squirrels, chipmunks, and porcupines are very fond of the plant. A variety of squirrels, including Red Squirrels, Abert Squirrels, and Flying Squirrels often use witches’ brooms for cover and nesting sites.

A surprising number of bird species rely on mistletoe. Studies by the USGS found that a high abundance of dwarf mistletoe in a forest means that a wider variety of birds and higher numbers of birds inhabit that forest. Also, since the lifespan of mistletoe tree hosts is considerably shorter than trees without mistletoe, a higher number of tree snags appear. This means that more cavity-nesting birds live in forests with abundant mistletoes. Among the birds that rely on mistletoe seeds are the Phainopepla (a silky flycatcher), Grouse, Mourning Doves, Blackcaps, Bluebirds, Evening Grosbeaks, Robins, Cedar Waxwings, and Pigeons.

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silky flycatcher with a mistletoe berry
A female silky flycatcher with a mistletoe berry in her beak. Credit: Todd Esque, USGS Western Ecological Research Center. Public domain.

Birds also find mistletoe a great place for nesting, especially in the dense and twisted witches’ brooms. In fact, northern and Mexican spotted owls and Cooper’s Hawk show a preference for nesting in witches’ brooms as do Great Gray Owls, Long-Eared Owls, Goshawks, and Sharp-Shinned Hawks, Gray Jays, Northern Beardless-Tyrannulet, Red Crossbills, House Wrens, Mourning Doves, Pygmy Nuthatches, Chickadees, Western Tanagers, Chipping Sparrows, Hermit Thrushes, Cassin’s Finches, and Pine Siskins.

Three kinds of butterflies in the United States are entirely dependent on mistletoes for their survival: Great Purple Hairstreak, Thicket Hairstreak, and Johnson’s Hairstreak. The Great Purple Hairstreak lays its eggs on American mistletoe, where the resulting caterpillars thrive on a mistletoe diet. The caterpillars of the other two butterflies feed on dwarf mistletoes. The Johnson’s Hairstreak is usually found in old-growth conifer forests in the Pacific states. The caterpillars of these butterflies closely mimic the appearance of the mistletoe with their mottled green and olive shades. The adults of all three species feed on the nectar from mistletoe flowers.

Mistletoe is also an important nectar and pollen plant for honeybees and other native bees. Mistletoe flowers often provide the first pollen available in the spring for the hungry bees.

How to make holiday decorations with mistletoe

Mistletoe can be cut from its host tree. Remove the roots by pruning the infested branch at least six inches below the spot where the mistletoe is attached. Wear gloves during harvesting or wash your hands immediately afterward to remove any toxins from the berries.

Refrigerate fresh-cut mistletoe sprigs to keep them fresh until you are ready to use them.

Use thin florist wire to wrap the ends of the mistletoe cuttings. Then add ribbons for color and your mistletoe is ready to hang for your holiday decoration. Do not hang the mistletoe sprigs directly above heaters, stoves, fireplaces, or any other source of heat, as the mistletoe will dry out much faster, creating a fire hazard. Mist the sprigs with water daily to keep them looking fresh.

Mistletoe berries are slightly toxic to children and pets: Accidental ingestion of American mistletoe can be harmful, so keep the plants out of their reach.

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