English Holly
Botanical Name:
Ilex aquifolium
Monitor List
General
- Native to Asia, Europe and Northern Africa.
- Cultivated commercially in the Pacific Northwest, for its foliage common in Christmas decorations.
- Consuming berries can cause vomiting and diarrhea in humans, dogs and cats.
- Invades native forest habitats where dense thickets suppress germination and growth of native trees and shrubs.
- A native alternative that is similar in appear to English holly is tall Oregon-grape. Oregon grape grows up to 10 feet tall, produces blue berries, and has compound leaves with 5-9 leaflets that are oppositely arranged with a single terminal leaflet, while English holly leaves are single and alternately arranged.
Identification
- Large, dense, slow-growing broadleaf evergreen tree or shrub. Generally growing 15 to 30 feet, but occasionally up to 50 feet tall.
- Grows as either a single tree or a multi-stemmed thicket. Bark is smooth and silver-gray in color.
- Leaves are thick, glossy, dark green and wavy, 1-3 inches long. Leaf edges usually have sharp spines, but may be smooth on older branches.
- Flowers are small, whitish, and sweetly scented. Typically blooms late April to mid-summer.
- Generally red, but sometimes yellow or orange berries ripen in the fall and persist throughout the winter; only female plants produce berries.
Photos
Habitat
- Tolerant of a wide range of soil, moisture and light conditions, allowing it to grow in a variety of sites.
- Grows in shade or sun in well-drained soil.
- Found in urban landscapes, undisturbed natural areas and native forests.
Reproduction and Spread
- English holly is dioecious, meaning plants are either male or female. In order for a female holly to produce berries it must be in close enough proximity to a male plant to be cross pollinated.
- Reproduces mainly by seed; birds eat the berries and disperse the seeds to new areas.
- Spreads vegetatively by producing suckers, and layering (branches root where they touch the ground).
Control
- Small plants can be pulled or dug up when soil is moist. All parts of the root need to be removed to prevent regrowth.
- Larger shrubs can be removed using a Weed Wrench, which can often be borrowed from your local county noxious weed control board.
- Large mature trees have deep extensive roots and are very difficult to dig up. Cutting is a better option for mature trees however, resprouts will occur so follow up treatment will be necessary.
Herbicide Control
- Foliar application is not recommended due to holly’s thick, waxy leaves that prevent the chemicals from being absorbed.
- EZ-Ject Lance Method: injects a small metal capsule of herbicide into the cambium layer of the holly and kills the roots, stems and foliage. Make sure to use the copperhead imazapyr herbicide shells as glyphosate may not be effective against holly.
- Cut-Stump Method: Cut the holly plant as close to the ground as possible and apply concentrated herbicide immediately to the cut portion. Apply herbicide to the whole cut surface but specifically focus on applying to the outer ring or cambium layer which will transport the herbicide to the root system.
- Hack and Squirt Method: Using an arborist chainsaw, hand saw, hatchet, or similar tool, cut downward-angled incisions, about 2 to 4 inches long and 1 to 2 inches apart. Make sure all cuts are below the last live branch, around the trunk. Cuts must penetrate through the bark into the living tissue and produce a cupping effect to hold the herbicide. English holly bark is quite thin so cuts do not have to be very deep. Using a chemical resistant spray bottle or a Nalgene wash bottle, carefully apply concentrated herbicide into the cuts.
- Herbicides containing the following active ingredient are effective on English holly:
- Imazapyr
- Apply during fall or spring.
- Cut stump treatment, apply undiluted solution.
- Hack and squirt, apply a 50% solution at intervals of 3-4 inches.
- Inject EZ-ject copperhead, insert 1 shell every 2-3 inches around the tree. Results will be visible within 6 months.
- Do not exceed 96 fluid oz of concentrated product per acre.
- Triclopyr
- Apply during fall or spring.
- Cut-stump treatment, undiluted solution.
- Hack and squirt, apply 1 ml of 50 to 100% solution at intervals of 3 to 4 inches.
- Glyphosate
- Apply during fall and spring.
- Cut stump application, apply undiluted solution. May result in excessive resprouting with very poor long-term control, best results in fall.
- Hack and squirt. Apply undiluted solution. Best results when applied in the spring.
- Imazapyr