Growing a grape holly plant in the landscape will offer unique interest to the area. Not only easy to grow and care for, but these lovely plants offer an abundance of food to wildlife through their fall berries. These plants will also add year-round interest through their attractive foliage color and texture.
I. Appearance and Characteristics
Oregon grape holly (Mahonia aquifolium) is a handsome, 3 to 6 foot (1-2 m.) ornamental shrub that can play a number of roles in the garden. The shrub’s appearance changes with the seasons. In spring, the branches bear long, hanging clusters of lightly fragrant, yellow flowers which give way to dark, blue berries in summer.
New spring foliage is bronze in color, turning green as it matures. In fall, the leaves take on a pleasing, purplish cast. Another grape holly plant, creeping Mahonia (M. repens) makes an excellent groundcover.
With foliage, flowers, and berries similar to the Oregon grape holly shrub, creeping grape holly has all the features of the taller form in a plant that grows only 9 to 15 inches (23-46 cm.) tall. The plants spread by means of underground rhizomes and seedlings often emerge under the plant where berries fall to the ground.
Although the berries are too sour to suit human taste buds, they are safe to eat and can be used in jellies and jams. Birds love them and disburse the seeds as they feed.
II. How to Grow and Care
Sunlight and Soil
Plant grape hollies in a partially shaded area with moist, neutral to slightly acidic, well-draining soil. M. aquifolium makes an excellent specimen or foundation plant and also looks good in shrub groupings or borders. When closely planted, the prickly, holly-like foliage forms a barrier that few animals will try to penetrate. M. repens likes full sun in cool climates and afternoon shade where summers are hot. Plant creeping Mahonia as a groundcover in a variety of situations. It serves to stabilize soil on slopes and hillsides, and is deer resistant, making it a good choice for woodland areas.
Watering
Water frequently in summer (every 2 days) and moderately the rest of the year.
Fertilizing
Fertilize in autumn with organic matter and mineral fertilizer monthly during spring and summer.
Planting Instructions
Prepare your site before planting:
- It is good to dig over the area where you intend to plant several months in advance. Destroy the weeds first: nettles, brambles and ground elder are tough and a glyphosate based weed-killer is the best way to remove them. Then dig the soil over; remove rocks, roots and other rubbish. Mix in well rotted compost or manure down to the depth of about 2 spades.
- If you have a heavy clay soil, it might be too difficult to dig over for most of the year. Heavy clay is fertile soil, so you don’t really need to improve it; killing the weeds is still necessary.
- Remember to water establishing plants during dry weather for at least a year after planting.
Planting accessories:
- Prepare your site for planting by killing the weeds and grass with Neudorff WeedFree Plus.
- If you are planting in an area with rabbit and/or deer, you will need to use a protective plastic spiral for each plant, supported by a bamboo cane.
- If your soil quality is poor, we recommend using mycorrhizal “friendly fungi” on the roots of new trees and shrubs.
- You can also improve your soil with bonemeal organic fertiliser and Growmore.
Pruning
Once they have established, Oregon grape plants will look their best when they are periodically cut down to stumps. This will make the plants more dense, bushy and keep them producing lots of flowers.
The best time to cut back your Mahonia is in spring, after the flowers fade.
It’s up to you whether to cut the whole plant down to stumps about 30cm high, or to cut back just the biggest stems, leaving the thinnest, youngest stems to provide cover while the rest of the plant grows back.
Propagation
Oregon Grape Holly can be propagated by seed, stem cuttings, or division of multi-stemmed parent plants.
Pests and Diseases
No serious pest or disease issues. It may be occasionally affected by rust and leaf spots, aphids, scale, and whiteflies.
III. Uses and Benefits
Oregon Grape Holly is perfect when massed in shady borders, woodland gardens, foundation plantings, and shade gardens.