A large shrub or small tree, English holly has become a serious invasive because of its adaptability to grow in shade or sun, and the ease with which its seeds are spread by birds. Seedlings are now commonly found in mixed deciduous and coniferous forests around the south coast, along the edges of wetlands and especially near residential areas.
Why is Holly so invasive?
Invasive holly competes with native shrubs and can suppress the natural regeneration of forest trees over time. Natural resource managers across the Pacific Northwest spend considerable resources to treat and control holly in an effort to preserve native forests.
How does English holly affect the environment?
English holly changes the composition of the environment. There is evidence that this plant alters soil conditions by adding large amounts of organic matter and sulphur. Large thickets will also outshade native shurbs and understorey plants.
Is English holly a pest?
English holly is a versatile, hardy plant combining year-round beauty and wildlife appeal. But when it escapes cultivation it can become an uninvited pest. My first encounter with English holly (Ilex aquifolium) was making holiday decorations in elementary school.
Is Holly poisonous to humans?
If stumps are left, English holly will re-sprout. This plant is adaptable to both shade and sun. English holly thrives in moist sites. Is common in both deciduous and coniferous forests. It can be found invading residential areas, wetlands, and forests of the south coast of B.C The berries are toxic to humans and pets if ingested.
Is English holly invasive?
English holly (Ilex aquifolium) is a Class C invasive species in Portland (see the Portland Plant List). It is a broadleaf evergreen tree or shrub that typically grows to about 6-15 feet tall. However, some plants can grow up to 50 feet tall. Leaves are dark green, lobed, leathery and glossy, with spiny edges.
Where is holly invasive?
Ilex aquifolium (English holly) is an evergreen shrub or small tree (family Aquifoliaceae) found in the North Coast Ranges, San Francisco Bay region and central coast of California.
Do holly bushes have invasive roots?
The root system is a taproot. This means holly bushes have one large root that grows straight down and then smaller, less hearty roots that spread out. The horizontal roots are responsible for gathering the majority of the nutrients needed to flourish. This type of root system can be invasive.
Is English holly native to North America?
Ilex opaca, the American holly, is a species of holly, native to the eastern and south-central United States, from coastal Massachusetts south to central Florida, and west to southeastern Missouri and eastern Texas....Ilex opacaSpecies:I. opacaBinomial nameIlex opaca AitonNatural range of Ilex opaca17 more rows
How do I get rid of English holly?
The most effective and time-efficient method to control English holly examined in this study is stem injection with imazapyr. This combination was very effective at killing the tree and resulted in the fewest number of trees with additional stump sprouts.
What is the difference between American holly and English holly?
Look at the color of the leaves. English holly has a deep green color and glossy finish. American holly leaves are a lighter, yellow-green with a dull sheen. Variegated leaves, ever popular during the holidays, indicate English holly.
Do holly trees cause subsidence?
It is difficult to give you a definitive answer to your question Sue but, if your Holly Tree is growing quite closely to the house subsidence damage caused by the roots can occur. This usually happens during very dry summers when the roots are searching for any available water.
Is it unlucky to cut down a holly tree?
The spiky leaves and blood-red berries are also associated with Jesus's crown of thorns. Many people believe it is unlucky to cut down a holly tree. This may be because of its reputation for protecting people and homes against lightning strikes.
Are holly trees good for the environment?
Our wildlife enjoys Holly, too: the berries are an important food source for many birds like Redwings and Fieldfares; indeed, Mistle thrushes guard their own berry-laden bushes with such voracity that they'll chase off any potential thieves.
How did English holly get to America?
Late 1700s: English holly brought to the eastern U.S. as a conservation effort to protect the American holly. It was quickly noted that it did not grow well in the east but did thrive in the PNW. This is where the use of English holly in place of American holly for Christmas décor slowly began.
Are American holly trees invasive?
The plant roots sucker, allowing dense thickets to form. The thickets cast deep shade, which affects nearby native vegetation. As a result, English holly is considered to be an invasive species in the Pacific Northwest, New Jersey, and Virginia.
Is English holly edible?
English holly and American holly are used as ornamental Christmas greens. The leaves of these and other holly species are used to make medicine. The berries are very poisonous and should not be swallowed.
Are American holly trees invasive?
The plant roots sucker, allowing dense thickets to form. The thickets cast deep shade, which affects nearby native vegetation. As a result, English holly is considered to be an invasive species in the Pacific Northwest, New Jersey, and Virginia.
Is Japanese holly invasive?
Japanese Holly (Ilex crenata) is a tier 2 invasive species in the Lower Hudson Valley, which means its just starting to emerge as an invasive species in our region. While Japanese holly is not one that is typically used in holiday decorations, however it has been planted as an evergreen decorative shrub.
Does anything eat holly berries?
Deer, squirrels, and other small mammals will devour Ilex opaca (American holly) and the berries are an important source of food for as many as 18 species of birds.
Are holly trees native to Washington state?
According to the USDA distribution map, English holly is reported as naturalized in Washington, Oregon, California, and Hawaii. Here in Washington, holly is mostly limited to western counties.
Why is English Holly considered an invasive species?
English holly has become a serious invasive because of its adaptability to grow in shade or sun, and how easy its seeds are spread by birds.
How tall do Holly trees get?
Female trees produce bunches of red, yellow or orange berries in winter that are poisonous to people but not to birds. Holly trees can range from 7 to 10m tall at maturity.
How Can I Identify English Holly?
Holly is a large, slow growing evergreen, usually found as a shrub or small tree. It has woody stems and its leaves are 2-5 inches long and 1-3 inches wide. The oval, shiny leaves are dark green on the surface, lighter green underneath, and young leaves have three to five sharp spines on each side.
Why Should I Care About English Holly?
Although not a state-listed noxious weed, holly is naturalizing and spreading throughout our area. Coniferous forests are particularly susceptible to invasion. Invasive holly competes with native shrubs and can suppress the natural regeneration of forest trees over time.
How Can I Control English Holly?
Because of its invasive nature, Clackamas County property owners are encouraged to remove holly plants. Replace them with non-invasive alternatives whenever possible. The GardenSmart Oregon guide to non-invasive plants lists lists many ornamental and native alternatives that provide similar function and appearance.
What is the English Holly?
English holly, a King County Weed of Concern, is a large, dense, slow-growing evergreen tree or shrub found throughout King County, from natural areas to native forests. Plants reach 15-50 feet tall and 15 feet wide. 1-3-inch-long, thick, glossy, dark green, wavy, and usually spiny leaves grow alternate on stems. Small, whitish, sweetly scented flowers lead in winter to red, yellow, or orange berries. Berries are poisonous to humans and pets. Reproduces mainly by seed, but also spreads vegetatively via suckering and layering. Birds eat the berries and spread the seeds to new areas.
Where is the English Holly native to?
English holly's native range is the British Isles to southern and central Europe.
How do holly berries spread?
Holly berries are dispersed by birds. Also spreads by suckering and layering.
Where can I find English Holly in Washington?
According to the University of Washington Herbarium records, botanists have collected specimens of English holly from naturalized populations in 17 western Washington counties, including King County.
Is a berry poisonous to humans?
Small, whitish, sweetly scented flowers lead in winter to red, yellow, or orange berries. Berries are poisonous to humans and pets. Reproduces mainly by seed, but also spreads vegetatively via suckering and layering. Birds eat the berries and spread the seeds to new areas.
Can you cut holly from the crown?
Mature trees have deep and extensive roots so digging is labor-intensive and results in considerable soil disturbance if all of the roots are removed. Cutting holly at the base usually results in re-sprouting from the crown, but with monitoring and follow up this can suppress the holly.
Is a Holly a male or female plant?
Collected plants have varied from immature plants to tall trees, and both male and female plants have been found. In some cases, the holly was growing as a single tree or in small, patchy populations, but in other cases, there were substantial populations noted that included a range of ages from seedlings to fruiting trees.
Identification and Reproduction
English holly is a slow growing perennial. It is evergreen and can take on a shrub or tree form.
Management
For alternative planting options to English holly download the ISCBC's Grow Me Instead brochure (pg. 21 and 22).
Resources
Download the Metro Vancouver's Best Management Practices for English Holly here.
Tansy Ragwort Curbside Pick-up 2021
Tansy Ragwort pick-up happening August 18th to September 1st for residents in the FVRD.
Why Is It a Noxious Weed?
This plant is on the monitor list - it is not a listed noxious weed in Washington. Please contact its sponsor Sasha Shaw at [email protected] to report locations or for more information.
How Do I Control It?
Please refer to the PNW Weed Management Handbook, or contact your county noxious weed coordinator.
For More Information
Article: Pictures of an invasion: English holly ( Ilex aquifolium) in a semi-natural Pacific Northwest forest
Overview
Description
Reproduction and Spread
- English holly is pollinated by bees so female trees must grow within bee range (100 feet or so) of a male to be pollinated
- Holly berries are dispersed by birds
- Also spreads by suckering and layering
Impacts and Distribution
- English holly is carried by birds into forests where it can form dense thickets that dominate the tall shrub layer and suppress germination and growth of native tree and shrub species. According to the USDA distribution map, English holly is reported as naturalized in Washington, Oregon, California, and Hawaii. Here in Washington, holly is mostly limited to western counties. Accordin…
Control
- Small plants can be pulled or dug up when soil is moist.
- Mature trees have deep and extensive roots so digging is labor-intensive and results in considerable soil disturbance if all of the roots are removed.
- Cutting holly at the base usually results in re-sprouting from the crown, but with monitoring and follow up this can suppress the holly.
- Small plants can be pulled or dug up when soil is moist.
- Mature trees have deep and extensive roots so digging is labor-intensive and results in considerable soil disturbance if all of the roots are removed.
- Cutting holly at the base usually results in re-sprouting from the crown, but with monitoring and follow up this can suppress the holly.
- Applying herbicide with the cut stump or frilling method are most effective. Foliar herbicide treatment is not very effective due to the thick, waxy leaves.
What to Do If You Find This Plant
- Because English holly is already naturalized in many places in King County and is not on the State Noxious Weed List, we are not tracking locations. However, if you know of any heavily infested forests, especially outside of the urban growth area, we would be interested in having that information. We are also gathering information on effective control methods. If you have had an…
For More Information
- For identification and control information, see King County English Holly Best Management Practices, or for a shorter summary handout see our English holly weed alert. For recommendations about alternatives to English Holly in landscapes, see the Garden Wise booklet or by contacting our office. For research findings, see our Holly Research and Reportspage.