7 Fascinating Facts About Holly Trees and Berries

Uncover holly tree facts, including if holly berries are poisonous, which holly tree is best for birds and how many species of holly exist.

All About Holly Berries and Trees

Haul out the holly! Of all the decorations we hang in the winter months, holly has one of the longest and most interesting histories. Holly berries are a great choice for attracting berry-loving berry-loving birds. Find out which holly tree is best for attracting your favorite feathered fliers. Then check out a few holly tree facts to impress your family and friends at the dinner table, too.

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1. Expert Tips on How to Grow a Holly Tree

robins eating holly berriesCourtesy Lindsey Davis
A flock of robins eating berries on a holly tree 

Garden expert Melinda Myers: Make sure you have the right growing conditions for hollies and enough room for at least one male for every one to five female plants. Without both, the female plants won’t produce berries. Hollies prefer moist, acidic soil, and evergreen hollies need shelter from winter’s cold winds and bright sun, which can both have a drying effect.

Check out the top 10 easy-care holiday houseplants.

2. Which Holly Tree Is Best for Birds and Wildlife?

holiday flowers and plants, american holly, cedar waxwingCourtesy Stewart Spielman
Cedar waxwing on a large American holly tree

Melinda says, “American holly (Ilex opaca) is native and may be a good choice. It’s a large tree that serves as a host plant for several caterpillars, and birds adore the berries. Or consider the deciduous winterberry (Ilex verticillata), a shrub that grows between 3 and 12 feet tall. It’s hardy in Zones 3 to 9 and loses its leaves in winter, revealing berry-covered branches.

Check out 10 small evergreen shrubs to grow for year-round curb appeal.

3. Are Holly Berries Poisonous to People or Pets?

Eastern bluebirdCourtesy David Sloas
Eastern bluebirds and other songbirds can eat holly berries, but they are unsafe for pets.

The next one of our holly tree facts might turn your stomach. Birders and gardeners know their feathered friends love to feast on holly bushes’ berries—technically, hollies have drupes, not berries, but we’re not going to get overly technical. But holly berries, leaves, and bark are all mildly poisonous because they contain theobromine, a substance similar to caffeine. In small amounts this won’t really affect humans, but large amounts can bring on stomach issues and more. (In fact, one species of holly native to the southeastern U.S., known as Yaupon holly, has the terrific botanical name Ilex vomitoria.) Native Americans even used some of these species in traditional medicines to induce vomiting.

While birds can handle the toxicity of the berries, pets like dogs and cats cannot. (Try these pet-friendly indoor plants instead). It’s best to keep live holly decorations out of your pets’ reach (psst—also hide the mistletoe), and be cautious when planting holly in your yard if your pets like to snack on your plants. And if you like to snack on your plants, consider planting these edible flowers instead.

Are poinsettias poisonous to cats and dogs?

4. There Are Hundreds of Holly Species

275055863 1 Judy Holman Bnb Bypc 2021Courtesy Judy Holman
Yaupon holly covered with waxwings

More than 400 species, in fact. They all belong to the genus Ilex, and they’re found around the world in tropical, sub-tropical, and temperate zones. In the U.S., you’ll generally find them growing in zones 6 to 10, with many native species available in most areas. (For those who think they live too far north to grow holly, look into the so-called “Blue Hollies,” a hybridized group said to be hardy to zone 4.) Learn everything you need to know about choosing and growing hollies from the Holly Society of America.

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5. “The Holly and the Ivy” Tells the Story of Christ

Close-up of English holly plant and fruitFeifei Cui-Paoluzzo/Getty Images
Close-up of an English holly plant

Although most of us only know the song’s first verse (“The holly and the ivy / When they are both full-grown” / Of all the trees in the wood / The holly bears the crown”) the later verses draw parallels between the thorny leaves and the crown of thorns Christ was said to wear, the bitter bark and his suffering, and so on. The holly referred to in the song, by the way, was English Holly (Ilex aquifolium), which is the only species that is native to most of Europe.

Psst—we love this Scandinavian Christmas tradition for the birds.

6. Holly Was a Winter Holiday Decoration for Thousands of Years

Ilex Vomitoria Tree And Red Fruits At Texarkana, Texas, UsaFeifei Cui-Paoluzzo/Getty Images
Bright red Yaupon holly berries

Long before Christians used holly to decorate their homes and churches at Christmastime, other cultures brought holly branches in to brighten things up in the winter. Druids used holly as part of their winter solstice celebrations at least two thousand years ago. Reportedly, they believe that the Holly King, having defeated the Oak King, rules over the darker winter months. (In the summer, the Oak king rules triumphant once again.) Romans associated holly with Saturnalia, celebrated around the same time. As Christmas became more popularly celebrated in the winter, holly naturally became a part of the festivities, as well.

If you enjoy holly tree facts, check out these surprising facts about holiday flowers and plants.

7. Holly May Protect You From Lightning Strikes

branch of Holly berriesMiguel Sotomayor/Getty Images
Holly leaves could protect your home during thunderstorms

While older cultures happily trimmed holly branches to bring indoors, they felt it was very bad luck to cut down a holly entirely. One popular belief was that the thorns on holly bushes drew lightning, keeping it away from homes and barns. Interestingly, there seems to be some scientific basis to this! According to the Holly Society, “We now know that the spines on the distinctively-shaped holly leaves can act as miniature lightning conductors, thereby protecting the tree and other nearby objects.” So feel free to prune your holly and cut branches for the holidays, but you might be tempting fate to cut it down entirely!

Next, we found 8 types of Christmas trees you can grow.

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Jill Staake
Jill lives in Tampa, Florida, and writes about gardening, butterflies, outdoor projects and birding. When she's not gardening, you'll find he reading, traveling and happily digging her toes into the sand on the beach.