How to grow Mahonia
Mahonia is a hugely popular shrub found growing in home gardens, parks, municipal planting, and supermarket carparks across the land. Perhaps a victim of its own success, mahonia’s ubiquitousness means its merits are often unfairly overlooked. One of the few flowering shrubs happy to grow in full shade, it offers year-round, handsome, architectural foliage, ‘out of season’ flowers in autumn, winter, or spring, and decorative blue-black fruit. It has excellent wildlife value too; the flowers support pollinators at times of otherwise scarcity, and the berries provide a welcome food source to many species of bird.
There are around 70 species of mahonia, all originating from Asia and the USA. Probably the most widely grown type here in the UK is Mahonia x media, a cross of two Asian species which forms a medium to large, winter-flowering shrub. The best-known cultivar of this is ‘Charity’, its flowers said to be the most strongly scented of all mahonias. Another favourite is M. aquifolium, a lower-growing, suckering, spring-flowering species from western North America often planted as ground cover. Its foliage turns red in winter, contrasting strikingly with the bunches of blue-black fruit which give this species its common name, Oregon grape. Also increasing in popularity are a few new compact forms suitable for smaller spaces and containers. Two autumn-flowering examples are M. ‘Cabaret’ with striking and unusual orange-red flowers, and M. ‘Sweet Caress’ notable for its unusually soft, prickle-free foliage.
Zantedeschia is a genus of flowering plants from the family Araceae and is native to southern Africa. With a rich history dating back to the Ancient Romans, these deciduous or semi-evergreen perennials have been used as a symbol of celebration. Zantedeschia was Named after Professor Giovanni Zantedeschia, an Italian botanist.
There are two main forms of Zantedeschia: hardy and tender. Hardy forms of the plant can be grown outdoors, enjoy moist soil and full sun or partially shaded conditions - these are known as Arum lilies. Tender forms of Zantedeschia prefer being grown in containers or pots and should be brought inside over the winter - these are known as Calla lilies.
With tuberous flora in all colours from whites, yellows and oranges to deep reds and purples, Zantedeschias are not to be overlooked in any garden, as long as they have sufficient sunlight to grow in.
Ready to learn more about growing Zantedeschia? Read on for all there is to know...
Key Information
Soil pH
Position
Hardiness
Where & when to plant Mahonia
Position - Partial to full shade. Full sun will be tolerated as long as the soil remains moist throughout summer. Try to minimise exposure to strong, winter winds.
Soil - The ideal is moderately fertile, humus-rich, moist, and well-draining. However, mahonia will grow in most soils aside from the extremes of waterlogged or parched.
Flowering Period - Can be autumn, winter, or spring depending on the species and cultivar.
Hardiness - Hardy. Mostly rated H4 (-5 to -10°C) or H5 (-10 to -15°C).
For best results, plant in autumn or spring. An autumn planting can be done by those gardening in mild conditions (and broadly speaking, this is the southern half of the UK). For those liable to cold winters, it is best to wait until spring (generally the northern half of the UK).
Whether you are planting mahonia as a specimen shrub, part of a border, or ground cover, it is a good idea to choose a spot which is sheltered from the wind – particularly for taller or less hardy species. Prickly forms make good intruder-proof planting, while compact varieties in containers are perfect for adding life to shady, unloved patio or balcony corners.
How to plant Mahonia
For planting into the ground, start by watering the plant well and allowing it to drain.
Dig the soil area over, removing any large stones and weeds and breaking up any lumps. Mix in a generous amount of organic matter such as manure or garden compost.
Rake level and firm with your heels. Rake level again.
Now dig the planting hole, aiming for twice the width of the rootball.
Place the plant in the hole, ensuring the top of the rootball sits level with the surface of the soil. Too low and the stem can rot, too high and the roots can dry out.
Backfill with soil and firm in gently with your foot.
Soak well with water.
Mulch around the base with well-rotted organic matter such as manure or garden compost.
For planting in containers first choose an appropriately sized pot. The best practice is to start just a few centimetres larger than the root ball and go up in size every year or so. Always ensure there are plenty of drainage holes in the bottom.
Again, water the roots thoroughly and allow to drain before potting.
It can be a good idea to fill and plant your pot in situ to save yourself the trouble of moving it once full.
Use a good quality potting compost with plenty of horticultural grit mixed in, and, if not already present in the compost (check the description on the bag) some slow-release fertiliser granules.
Start by partially filling the pot with compost; enough so that when placed on it the top of the roots sit about 3cm lower than the top of the pot.
Infill all the space surrounding the roots with compost, firming down with your fingers then adding a little more so the plant is held tight.
Pick up the pot (if you can!) and lightly tap on the potting bench or ground a few times to help further settle the compost around the plant.
Soak well with water.
A mulch with horticultural grit will look attractive and help to prevent a ‘cap’ or crust forming on the top of the compost (something container plants can suffer due to the artificial nature of their watering).
What to plant with Mahonia
Unlike many shrubs mahonia copes well with root competition, meaning you can plant right up to its base. Go for an underplanting of similarly shade-loving companions such as brunnera, bergenia, hosta, periwinkle, hellebore, sweet woodruff, violet, and epimedium. Spring bulbs such as chionodoxa and erythronium will add a dash of fleeting, twinkling colour, and of course no shady spot would be complete without a variety of ferns dotted and woven throughout.
How to care for Mahonia
Pruning and Deadheading
Most of the time mahonia quietly does its thing, needing little attention other than a spot of light tinkering in spring. Simply remove faded leaves along with any unsightly stems you feel may be spoiling the look or shape of the shrub. You can take it a little further if you like by selectively pruning out any of the less impressive leaf rosettes to reveal the better-looking ones and thinning out branches to create a more spacious appearance.
Occasionally, a hard prune may be called for. Perhaps a spreading, suckering species is starting to outgrow its allotted space, or a larger shrub has become bare at the bottom. (Some gardeners find the bare stems attractive and welcome this development, though others prefer the dense, compact form achieved with pruning).
To reduce the spread of a suckering species, simply dig out unwanted growth with a sharp spade. The rest can be cut back to just above ground level if it’s looking tired and in need of fresh vigour.
To renovate a leggy, bare shrub, cut the whole lot back in late winter or early spring to around knee height. Feed, water, and mulch as below and expect it to shoot back quickly with plenty of bushy growth.
Watering
Give a good soak on initial planting, and then regularly throughout the first growing season in the ground. Once established, mahonia is drought tolerant and should require watering only in the most prolonged periods of hot, dry weather.
Container grown mahonia has less access to moisture so needs regularly watering throughout every growing season. Allowing the top couple of centimetres of compost to dry out between watering is a useful rule of thumb to help avoid overwatering. Use your finger inserted into the compost to check this, being aware that in the height of summer watering can be needed every day. From mid-autumn, the British climate tends to take over watering needs, though do remember to step in in the event of an unseasonably dry spell.
Feeding
In healthy, fertile soil, a mulch of well-rotted organic matter (i.e., a layer of leaf mould, manure, or garden compost applied to the soil around the plant) should provide sufficient nutrients for your mahonia. This has the added benefit of suppressing weeds and locking in moisture. Mulch when planting, and then again each spring.
If you feel your mahonia could do with a boost (perhaps you garden on poor soil or have just carried out a renovation prune), a dose of balanced fertiliser such as blood, fish, and bone can work wonders. Do this in spring, ideally in conjunction with mulching. First apply the feed, lightly fork into the surface of the soil, water, then mulch.
Container-grown plants rely solely on the gardener for nutrition and therefore need a little more attention when it comes to feeding. Get off to a flying start by making sure you use a good quality compost with slow-release granules mixed in, then throughout the growing season (March to October) apply a balanced liquid feed once every three to four weeks. Remember also to repot your mahonia every few years into a larger pot with fresh compost. When this is no longer feasible, we advise a top dress each spring. Simply scrape away the top few centimetres of compost and replace with fresh (not forgetting to mix in some slow-release granules).
Cold Protection
Most mahonias (with the exception of a few lesser-known half-hardy species) are tough enough to withstand an average UK winter without the need for additional protection. The biggest threat to winter survival is strong, cold wind and waterlogged soil, so spend time initially choosing a sheltered, well-draining position. An ideal spot may be tucked in amongst other shrubs and trees, or on the leeward side of a hedge, wall, or fence.
Like all plants, mahonia grown in a container can be more susceptible to cold damage. If you experience harsh winters, it can be worth wrapping the pot in an insulating layer of hessian, fleece, or bubblewrap. As well as protecting the roots, this helps prevent frost damage to the container itself.
Pests and Diseases
Mahonia is largely trouble-free, though you may occasionally spot rust or mildew; particularly on the spreading, groundcover species M. aquifolium. The best line of defence is to grow healthy, thriving specimens, which means ensuring optimum levels of water, light, and air flow. Prune off and dispose of any affected plant material, then water, mulch, and prune lightly to improve the movement of air throughout the shrub. If necessary, thin out surrounding planting for the same purpose.
How to propagate Mahonia
We find the best way to propagate mahonia is taking semi-ripe cuttings from late summer to autumn:
Look for current year’s growth which is firm and woody at the base, while still soft and pliable at the tip. You’re aiming for a cutting of 10 centimetres or less (any longer and they are more likely to dry out and fail).
Using a sharp knife or secateurs, sever the cutting from the plant and put in a plastic bag straight away to maintain moisture content.
Fill a pot (or several, if you have a lot of cuttings) with a perlite-heavy compost mix (at least 50% perlite).
Trim the end of the cutting to just below a node (point at which leaves grow).
Remove lowest leaves and soft tip, leaving 2-4 leaves.
If the remaining leaves are large, cut them in half with a sharp knife (to reduce water lost through transpiration).
Insert the cuttings into the compost and water lightly. Several cuttings can be put in the same container if there is enough space to do this without them touching.
Place in a greenhouse or propagating unit if you have one or covered with a plastic bag on a windowsill if not (out of direct sunlight).
Keep the cuttings misted and occasionally watered until they root. You will know this has happened when roots emerge out of the bottom of the container.
Gently remove rooted cuttings and pot them into individual pots. Grow on in a cool yet frost-free environment such as an unheated conservatory, greenhouse, or cold frame, until they are large enough to be planted out as above.
Many plants carry Plant Breeders Rights and cannot be propagated for commercial purposes.
Common Mahonia Questions
Does mahonia grow quickly?
Mahonia has an average growth rate. Smaller forms can be expected to reach full size in 5-10 years, larger shrubs in 10-20 years.
Where does mahonia grow?
Mahonia is relatively forgiving when it comes to growing conditions, though its ideal is a sheltered spot in partial shade with reasonably fertile, well-draining soil.
Is mahonia an invasive plant?
Although some species of mahonia are classed as invasive in the USA, those popularly cultivated in the UK are well-behaved garden shrubs which do not pose a problem.
Is mahonia the same as berberis?
Mahonia is in the berberis family (berberidaceae). Although distinct genera the two are closely related, and you may occasionally find mahonia labelled generically as berberis.
The bark of my mahonia has cracks in it. Is this normal?
Yes, fissured bark is a characteristic of many mahonia species and considered a decorative feature.
Can you eat the berries of mahonia?
Yes! They’re too acidic to eat raw, though make delicious jelly, jam, and wine (that’s if the birds don’t get to them first).
