Mistletoe is a parasitic plant that grows on trees, particularly hardwood trees like oak, maple, hickory, poplar, and apple. It has green leaves and white berries that emerge in the winter, typically between October and December. The berries on mistletoe are white, sticky, and contain one or two seeds. But what exactly are these mistletoe berries? Let’s take a closer look at the botany behind this iconic holiday plant.
The Anatomy of Mistletoe Berries
The mistletoe berries that we commonly associate with Christmas and kissing under the mistletoe are produced by plants in the Santalaceae family. There are over 1,300 species of mistletoe, but the ones most relevant to the Christmas tradition belong to the genera Viscum and Phoradendron.
Specifically, the mistletoe varieties that produce the familiar white berries are:
- European mistletoe (Viscum album)
- American mistletoe (Phoradendron leucarpum)
The berries emerge from small yellow or white flowers. Once pollinated, these flowers develop into white or pinkish berries that consist of:
- Fleshy fruit wall (pericarp)
- Viscin layer (sticky substance)
- Seed(s)
The fleshy fruit wall surrounding the seeds is called an utricle. The berries are classified as drupes, a type of fruit with thin skin and flesh surrounding a pit or stone that contains the seed.
Other well-known drupes include cherries, peaches, plums, and olives. But unlike these fruits that contain just one pit/seed, mistletoe berries contain one or two seeds, each surrounded by a separate utricle.
The viscin layer between the fruit wall and seeds contains polysaccharides that make the berries extremely sticky. This stickiness helps the seeds adhere to the bark of trees after being eaten and passed by birds.
Botanical Role of Mistletoe Berries
The primary purpose of mistletoe berries is seed dispersal. Mistletoe is an obligate hemiparasite, meaning it gets water and nutrients from its host tree but still produces its own food through photosynthesis.
Birds play an important role in dispersing mistletoe seeds. The berries provide an attractive food source for birds during winter when other fruits are scarce. As birds eat the berries, the seeds pass through their digestive systems and are deposited onto branches sticker-first thanks to the viscin.
Once on a new branch, the seeds can germinate and grow roots down into the host tree. A seedling will then emerge and start developing into a new mistletoe plant, perpetuating the parasitic life cycle.
Some key birds that help disperse mistletoe include:
- American robin
- Cedar waxwing
- Bluebird
- Robin
- Blue jay
- Spotted towhee
While birds aid mistletoe spread, the berries themselves are toxic to humans in large doses. So enjoy a few for the holiday aesthetic but don’t overindulge!
Cultural Significance of Mistletoe Berries
In addition to their biological role, mistletoe berries have cultural significance in winter holiday traditions across Europe and North America. Some highlights include:
- Kissing under mistletoe – Kissing under a sprig of mistletoe is a Christmas tradition first practiced in 18th century England. Each kiss plucked a berry off, with the kissing finished after all berries were picked.
- Mistletoe in Christmas decor – Mistletoe is commonly hung in doorways and ceilings during Christmas as decoration and to inspire kisses.
- Celtic mythology – Druids believed mistletoe possessed mystical powers relating to fertility, protection, and even warding off evil spirits.
- Norse mythology – Some legends link mistletoe to the Norse god Baldur’s death and resurrection.
- Medicinal uses – European mistletoe has historically been used as medicine for ailments like epilepsy, infertility, and arthritis. However, ingestion is now discouraged.
The mystical associations with protection, fertility, vitality, and holiday romance have solidified mistletoe berries as a classic component of Christmas symbolism.
Are Mistletoe Berries Toxic?
While mistletoe berries may look tempting, they are best admired from a distance. The white glutinous pulp around the seeds can cause digestive upset and cardiovascular problems if ingested.
Specifically, mistletoe berries contain toxic compounds like:
- Phoratoxin
- Tyramine
- Choline
- Acetylcholine
- Histamine
Ingesting even a few raw berries can cause issues like:
- Stomach pain
- Nausea and vomiting
- Diarrhea
- Blurry vision
- Difficulty breathing
- Low blood pressure
- Hallucinations
- Seizures
- Cardiac arrest in severe cases
Despite the dangers of raw mistletoe, there are medicinal teas and extracts made from the leaves and stems, not the berries. But ingestion of any mistletoe plant parts is not recommended without medical supervision.
The FDA advises keeping mistletoe berries away from children and pets and avoiding consumption of the raw plant. So while it’s fine to decorate with mistletoe, leave the berries alone!
Comparison of Mistletoe Species and Berries
There are over 1,300 species of mistletoe found worldwide. The appearance and toxicity of mistletoe berries varies somewhat between the different species.
| Species | Region | Berry Color | Toxicity |
|---|---|---|---|
| European Mistletoe (Viscum album) | Europe, Asia, Africa | White | Highly toxic |
| American Mistletoe (Phoradendron leucarpum) | Eastern North America | White | Mildly toxic |
| Dwarf Mistletoe (Arceuthobium ssp.) | North America | Orange, red | Toxic |
| Viscum cruciatum | Southeast Asia | Yellow, orange | Mildly toxic |
| African mistletoe (Erianthemum dregei) | Africa | Pink, red | Toxic |
As shown above, the most common mistletoe varieties used in Christmas decor are Viscum album and Phoradendron leucarpum. Both produce white, sticky, toxic berries – but American mistletoe berries are less dangerous if ingested.
The dwarf mistletoes commonly seen as bushy masses in tree tops produce red or orange berries. These smaller mistletoes are more distant taxonomically from Viscum and Phoradendron.
While yellow, orange, pink, and red mistletoe berries exist, the white berry varieties are most synonymous with Christmas and midwinter traditions.
Conclusion
The berries found on mistletoe plants are modified fruits containing one or two seeds surrounded by a sticky pulp. While the generic term is mistletoe “berries”, botanically they are classified as drupes. These berries are produced by mistletoe species in the Viscum and Phoradendron genera.
Birds play an integral role in dispersing the seeds found within the berries. Once deposited on a new tree branch, the seeds can sprout and grow into a new parasitic mistletoe plant.
While the berries serve this important ecological purpose, they should not be consumed by humans. The seeds and pulp contain toxic compounds that can cause digestive, cardiovascular, and neurological problems.
But the mystical associations and vibrant appearance of mistletoe berries have secured their status as a holiday decoration. As long as they are simply admired and not eaten, these berries can be safely showcased and incorporated into Christmas traditions and botanical fascination.
