Mahonias are fantastic evergreen plants, with clusters or spikes (racemes) of scented yellow flowers that are rich in nectar and a magnet for foraging bees in winter. The different species of Mahonia come in a range of sizes to suit any garden type, and flower at different times from late autumn to early spring.
Mahonia or Berberis?
Mahonias are members of the Barberry family (Berberidacae). However, botanists haven’t completely agreed on the nomenclature. Don’t be confused (as I was) if you see the same plant with two different names: Berberis and Mahonia. Mahonia aquifolium is also sometimes known by its common name of Oregon grape (Oregon adopted it as its official state flower in 1899) .
Best features of Mahonia
Mahonias tend to be planted for their bold architectural foliage. Most Mahonias are large shrubs with rows of glossy, deep green, spine-toothed leaves. However, there is a variety called Mahonia eurybracteata ‘Soft Caress’ that has spine-free foliage if you are looking for something softer.
The biggest delight is the characteristic clusters of scented yellow flowers. These are followed by pretty purply-blue berries.
Mahonias tolerate all types of well-drained soil, and will thrive in sun or shade. This makes them a good choice for ‘problem’ areas of the garden. Most are fully hardy, down to –15oC.
Key factors when choosing a Mahonia
To find the right Mahonia for your garden it is worth considering both size and flowering time. Although there are about 70 species of Mahonia, a few key varieties tend to be sold by garden centres or online retailers in the UK.
Mahonia x media ‘Winter Sun’, ‘Charity’ and ‘Lionel Fortescue’ can grow to 2.5–4 metres in height, although they can taken 10–20 years to reach their ultimate size. Being large upright shrubs, these varieties are ideal as a focal point at the back of a border. Sometimes they are used as hedging. They tend to flower between late November and early January.
Mahonia japonica is smaller than the ‘Media’ varieties, but is another erect shrub that can grow to 1.5–2 metres in height. It also flowers between the end of November and March.
Mahonia aquifolium ‘Apollo’ is a more compact variety that grows in a low spreading dome. It reaches about 1 metre in height and spreads to about 1.5 metres.
I pass this one on my daily dog walk. It has been bursting with compact clusters of intensely scented flowers all through February. It is thriving in a sheltered walkway next to a fence where it gets both sun and shade.
Mahonia repens has a low, creeping habit, with a height of 30–50cm and spread of 1 metre. It is ideal for shady ground cover, at the front of a border, or to cover a bank. This variety flowers in mid to late Spring (April/May).
Planting Mahonia
March is a good time to plant Mahonias. Make sure you choose a spot where your variety of choice has enough room to grow. I initially planted my Mahonia japonica too close to a conifer hedge and had to move it (see Mahonia on the Move). Dig a hole that is twice the size of the root ball. Plant the Mahonia with some well-rotted compost and firm it in well before giving it a good soak.
Mahonia care
Mahonias are low maintenance plants. They have low nutrient requirements, but like most shrubs will appreciate a mulch in early spring and/or autumn. This will also help to suppress weeds around the base. They can tolerate relatively dry conditions, so they only need watering in times of drought.
Pruning. Thankfully, pruning can be kept to a minimum, not least because the holly-like leaves can make it an uncomfortable process. In fact, you don’t need to prune a Mahonia at all unless your shrub loses its shape or gets too leggy.
If you do need to prune, make sure you are wearing a sturdy pair of gardening gloves. After flowering, remove any dead or diseased branches, or any branches that are growing out at an awkward angle or crossing with other branches.
If your Mahonia has become bare at the base, you can give it a hard prune by cutting a third of the branches down to about 15 cm (6 inches) from ground level. It will look a bit sorry for itself for a while, but this will help to generate fresh growth from the base.
To make plants bushier, cut back branches by 30–50%, which will stimulate the production of side shoots.
Avoiding disease. In general, Mahonias remain pest and disease free. Powdery mildew and rust are potential problems though. To help avoid these, make sure you water at the base of the plant and not on the leaves, regularly remove dead leaves and material from around the plant, and prune out a few central branches to let air circulate through the plant. Remove any affected leaves as soon as the problem appears so that it does not spread to the rest of the plant.
Go get a Mahonia
In summary, a Mahonia will add winter colour and nectar to your garden, will grow pretty much anywhere, and will be relatively low maintenance. So, if you have the room, I highly recommend you go out and get a Mahonia.
