A splash of color in a winter garden is always a heartwarming sight. In this article, we’ll take a look at the genus Mahonia, a fantastic winter flowering shrub or small tree, and some of the many beautiful species you can grow.
- What Is a Mahonia Plant?
- Selected Mahonia Species and Hybrids
- How to Grow Mahonia
- Mahonia Care and Maintenance
What Is a Mahonia Plant?
Mahonia is a genus of shrubs or small trees which are native to Asia and the Americas. These plants are commonly known as Oregon grapes, holly grapes or holly leaved barberries.
The plants characteristically have large compound leaves with spiny leaflets. The leaves are typically 4-20 inches(10-50cm) long and hold 3 to 15 leaflets.
There are around 70 species of Mahonia, many of which are great for use in the garden, and furthermore, many varieties and hybrids have been developed. These plants are evergreen and can withstand relatively cold conditions.
Mahonia flowers are born on terminal clusters or spreading racemes. These plants generally flower in winter, although blooms may occur in late fall or early spring.
This flowering period makes them a very useful addition to the garden, providing winter color to the landscape when many other plants show little sign of life or color.
Most Mahonia species produce a profusion of bright yellow flowers, which may be mildly fragrant.
Selected Mahonia Species and Hybrids
Here are some common types of evergreen mahonia bush:
The creeping mahonia is a small species native to the northwest of North America. It has a creeping growth form and usually reaches a height of just 1.5ft (45cm) and a width of around 3ft (90cm).
A neutral to acidic soil is preferred which can be sandy, loam or clay-based. A fast-draining, moist soil is, however, preferred.
This spring-flowering species prefers a little more sunshine and should be planted in partial shade to full sun. The creeping mahonia is deer resistant and can be grown in USDA Hardiness zones 5-8.
Perhaps the best known of the Mahonias, this was also the first described in the genus. M. aquifolium or Oregon grape is native to North America, from southern Alaska, and Canada, south to California and New Mexico.
This is a fairly tall mahonia tree that may reach 6ft (1.8m) in height and 5ft (1.5m) in width. M. aquifolium produces fragrant yellow flowers in the spring which are pollinated by bees and butterflies and the fruits are enjoyed by a variety of birds. Fortunately, deer are not attracted to the spiny leaves of this plant.
This evergreen shrub can be grown in much the same soils as M. repens and is relatively drought tolerant once established.
This plant does not enjoy full sun and should be grown in partial to full shade. Oregon grape can be grown in USDA Hardiness zones 5-8.
The Japanese mahonia is, in fact, thought to be native to Taiwan, although it has been grown in Japan for centuries.
This is a larger species reaching a height and width of around 10ft (3m). It should be grown in a fertile soil in partial to full shade and will produce fragrant flowers in the fall.
Although M. japonica is less cold hardy than the previous species, it is hardy to USDA zones 7 and 8. The leaves of this species take on an attractive red to purple hue in the colder months.
The Leatherleaf Mahonia, or Beal’s mahonia is native to China and most popular for its large interesting leaves. They are of a blue-green color and leathery texture.
This is a large species, reaching up to 12ft(4m) tall and 10ft (3m) wide. M. bealei is a shade lover which should be grown in full to partial shade.
Unfortunately, this plant has been found to be invasive in the following states: Alabama, Illinois, Ohio, Kentucky, Virginia, Maryland, Delaware, North Carolina, South Carolina, Tennessee, Georgia, Mississippi, and Florida.
M. aquifolium would be the better, indigenous, choice if you’re looking to plant a mahonia in one of those areas.
Among the largest of the mahonias, this handsome species is native to China. The Yunnan mahonia or Chinese hollygrape tends to grow from a single stem and generally reaches heights of around 15ft (5m), although much larger specimens have been recorded, up to around 30ft (9m).
M. lomariifolia also has larger leaves than other species, with up to 41 leaflets. This species grows at a moderate pace and can be grown in partial shade to full sun, in USDA hardiness zones 8-9.
Mahonia x media
This popular variety is a hybrid between M. japonica and M. lomariifolia. It is a large variety reaching the size of the Chinese mahonia and often with a single stem and upright shape.
These plants may develop beautiful deep red foliage in the fall, giving them an eye-catching appeal.
This variety was developed in Ireland in the 1960s. It is known to be a smaller plant than other M. x media varieties and produces more fragrant blossoms
This clone is cold hardier than others and was selected in Seattle in the 1960s. The M. x. media hybrids can be grown in USDA hardiness zones 6-9.
How to Grow Mahonia
Mahonias can be grown from seed, stem cuttings, layering or division. Seeds sown from hybrid plants may not produce plants with the same characteristics as the parent plant, so growing clones from cuttings is the best option there.
Growing these evergreen shrubs from seed can be as simple as lightly burying ripe berries towards the end of summer or beginning of fall and waiting, with fingers crossed, for seedlings to appear the following spring.
To increase your success rate, roughly remove the flesh from the black berries, as would be the case in nature where a fruit-eating bird or other animal has snacked on them. Then stratify the seeds by keeping them in a cold environment(just above freezing point) for a period of at least a month.
After that, keep the seeds at a warmer temperature of around 65 degrees F (18℃) for at least another month. The seeds can then be kept cool again for another period or be planted in a good sterile substrate.
This may seem complicated but what you’ve done is to mimic the conditions of nature that break the dormancy of a seed and encourage it to germinate.
4-6 inch(10-15cm) cuttings of these plants take well when dipped in rooting hormone powder. Remove the foliage from the bottom half of the stems before treating and keep the cuttings in a warm, moist environment until roots are established.
These plants do not enjoy strong, cold winter winds so select a sheltered site if possible.
Mahonias are generally slow-growing plants that will appreciate a rich soil, so take the time to mix in some compost or organic material into the substrate before planting.
Mahonia Care and Maintenance
These are very low maintenance plants that can be pruned once a year or every other year. Often all they require is the removal of untidy old dead stems.
Mahonia, however, tolerates heavy pruning and can be cut right down if you’re unhappy with its shape. Being a slow grower, it may take a few years to grow back to size.
Mahonia plants should be watered regularly during their first year to encourage the establishment of a strong root system. Mulching will assist in maintaining moisture to the roots during this time.
A slow-release fertilizer or a fresh layer of rich mulch provided once a year is enough to keep your plant growing well.
These are great landscaping plants with interesting evergreen foliage and beautiful flowers. Their fall to spring flowers add color to the landscape when not much else may be flowering.
It is important to consider the specific needs and growth forms of different mahonia species before selecting one for landscaping uses. As described earlier in this article, species vary tremendously in size and light requirements.
The small prostrate mahonias make great ground cover plants, which can even be used in rockeries, while the larger shrub form species can be used as hedges and screens. The spiky leaves of these plants make them ideal for use as an attractive natural security hedge along perimeters.
The larger upright species such as M. lomariifolia and the M. x media hybrids make fantastic specimen plants.
While mahonia shrubs make great plants for shady foundation planting, these plants should not be planted along walkways or in areas where people or pets are likely to brush against them due to their prickly nature.
Medicinal And Food Uses
These plants have been widely used in traditional Chinese medicine to treat a range of conditions including tuberculosis, eczema, wounds and dysentery among others. (1)
The berries of these plants are edible although somewhat tart in flavor. They contain high amounts of vitamin C and antioxidants.
It’s best to eat them after a few nights of frost as this apparently sweetens the berries. The seeds are said to be bitter and should be discarded.
The fruits of Mahonia contain a compound known as Berberine which, if eaten in large amounts, can cause some pretty unpleasant side effects. Moderation is therefore advised.
Can Mahonia be grown from cuttings?
Yes, Mahonia can be propagated from cuttings. Take 4-6 inch (10-15 cm) stem cuttings in spring or early summer, dip them in rooting hormone, and plant them in well-draining soil. Keep the soil moist until the cuttings establish roots and show signs of new growth.
Why does my Mahonia not flower?
Several factors can contribute to a Mahonia not flowering. Common reasons include insufficient sunlight, improper pruning, or a lack of chilling hours for certain Mahonia varieties. Ensure your Mahonia receives adequate sunlight, avoid heavy pruning during the flowering period, and check if your specific Mahonia variety requires a certain amount of chilling hours to initiate blooming.
Mahonias are deservedly prized for their fantastic winter floral display. This coupled with their hardiness and low maintenance requirements, and the variety of sizes and shapes available, make this a plant you should definitely consider for your garden.
Check our blog for more types of bushes to grow.
(1) He JM, Mu Q. The medicinal uses of the Mahonia genus in traditional Chinese medicine: An ethnopharmacological, phytochemical and pharmacological review https://pubmed.ncbi.nlm.nih.gov/26387740/
(2) Jaca, T., P. & Mkhize, M., A. Mahonia oiwakensis Hayata (=Mahonia lomariifolia) (Berberidaceae): A new species for the alien flora of South Africa https://journals.abcjournal.aosis.co.za/index.php/abc/article/view/2285/2331
*image by ottochka/depositphotos