How Mistletoe Works - People | HowStuffWorks

Mistletoe is a parasitic plant that grows on trees, particularly hardwood trees like oak and apple. A parasite is a plant or animal that needs another plant or animal to survive. As mistletoe grows on a tree it uses its roots to invade a tree's bark, which allows mistletoe to absorb the tree's nutrients. Sometimes, mistletoe can harm a tree and cause deformities in a tree's branches, but usually it doesn't kill its host. If the host dies, the mistletoe dies. Phoradendron flavescens and Viscum album are the species associated with Christmas.

Mistletoe can produce its own food by photosynthesis (autotropic), and live on its own, but it prefers to grab water and nutrients from its host tree (heterotrophic). It's common for a mistletoe plant to grow on top of another mistletoe plant. If that happens, researchers from the University of California, Riverside found that the mistletoe plants may "share the tree" and rely more on photosynthesis for food to lessen the harm caused to the host tree.

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Mistletoe is easy to spot in the winter because its leaves stay green all year long. In the United States, it grows in tropical and subtropical regions (from New Jersey to Florida). Mistletoe has pointy, green, leathery leaves, with waxy berries that are either red or white. The plant's flowers can be a wide variety of colors, from bright red to yellow to green.

Birds eat the berries that grow on mistletoe and eventually leave their droppings at their favorite hangout spot — a tree branch. The droppings contain seeds that sprout roots into the tree branch. The birds also help spread the seed by wiping their beaks on the tree bark to clean off the sticky seeds after they've eaten. The seeds are sticky because of the juice inside the berry. This stickiness helps the seeds stay in the tree rather than falling to the ground. Within six weeks, the mistletoe plant begins growing, although it takes several years to flower.

Is Mistletoe Poisonous?

The National Capital Poison Center notes that American mistletoe (Phoradendron serotinum) appears less toxic than the European variety (V. album) and "doesn't deserve its toxic reputation." However, since most people may not know what kind of mistletoe they may be standing under, the safest thing to do is call poison control if you or someone you know has swallowed mistletoe. If you have mistletoe in your house this holiday season, be sure that it is in a place where children and pets won't be able to get to it.

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