Pruning and Deadheading

If you can it’s best to leave berberis untouched, as it flowers and fruits on the previous year’s growth. This means pruning, no matter when you do it, will always interrupt the display in some way.

If you need to restrict size or your berberis is becoming congested, our advice is as follows.

Deciduous species can be pruned in mid to late winter:

• Remove any dead, diseased, damaged, or spindly growth at ground level, then go on to take out some of the older stems, also at ground level. If you need to restrict size, you can take the remaining stems back to a set of healthy buds.
• An alternative way to restrict size whilst creating a more natural shape is to coppice (i.e., cut the whole thing down to just above ground level) every few years in late winter or early spring. Be aware that this will mean no flowers or fruits the following year, though normal service should be resumed after this.

Evergreen species can be shaped lightly immediately after flowering, or again, hard pruned (coppiced) down to just above ground level in early spring.

Hedges are best trimmed straight after flowering.

Watering

Like all trees and shrubs, berberis should be regularly watered during its first year or two in the ground. After this, it should only need watering in prolonged dry spells. When watering, give a deep, thorough soak then allow the top few centimetres of soil to dry out before repeating (this encourages the formation of deep roots, as opposed to watering little and often which can result in roots growing mainly in the surface of the soil). To check this, wiggle your finger down into the soil until you hit damp.

Container-grown berberis have less access to moisture so need regularly watering throughout every growing season. Again, water deeply and allow the top few centimetres of compost to dry out before repeating, though be aware that in the height of summer this can happen very quickly and some container-grown plants may need watering every day (particularly those in smaller pots). 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

On most soils, a mulch of well-rotted organic matter (i.e., a layer of manure or garden compost applied to the soil around the plant) should provide enough nutrients for your berberis. This has the added benefit of suppressing weeds and locking in moisture. Mulch when planting, and then again each spring.  

If you feel your berberis could do with a boost, particularly if you’ve given it a hard prune, applying a general-purpose granular feed to the surface of the soil and lightly working in (known as a ‘top dress’) can reap benefits. Do this when mulching in spring – first apply the top dress, then cover with the mulch.

Container-grown berberis is different, relying solely on the gardener for nutrition. Get off to a flying start by making sure you use a good quality compost with some slow-release fertiliser granules mixed in. After this, carry out a replenishing ‘topdress’ annually in spring, simply scraping away the top few centimetres of compost and replacing with a fresh load (also with slow-release fertiliser granules mixed in). Remember also to repot your berberis every few years, going up slightly in size each time until it reaches full size.

Cold Protection

The majority of popular berberis species and cultivars can withstand even a cold UK winter without the need for additional protection. Having said this, some of the deciduous species (particularly B. thunbergia and its cultivars) can suffer scorched shoot tips during a late frost, so it is best to plant these in less exposed positions.

Some of the more unusual species (e.g., B. cretica, B. libanotica, B, cooperi, B. wallichiana, B. chingii, and B. goudotii) are less hardy and will benefit from winter protection or a sheltered environment.

Pests and Diseases

The most significant problem faced by this shrub is the berberis sawfly – a pest which has spread rapidly throughout the UK over the last couple of decades. In its larval stage it can defoliate a shrub at an alarming rate. Look out for signs from April to October and use an organic spray as soon as you spot anything. Mature specimens tend to recover from an attack, though may be weakened by repeated infestations.

Another issue you may spot is a fungal disease known as powdery mildew. This appears as a white, powder-like coating on the foliage and is generally a sign that a plant is stressed – often through lack of water – though other causes can include poor airflow, over fertilizing, and insufficient sunlight. Prune off and dispose of any affected leaves if you can, and thin out stems to improve airflow and light levels. A little TLC also works wonders, i.e., a good soak and a mulch.

You may also spot aphids crowding along the stems, particularly on new shoots. Our advice is that these are part of a balanced garden ecosystem and the best approach is to leave them to their natural predators (e.g. birds, ladybirds, and wasps). When numbers are so large, however, that their feeding starts to inhibit and disfigure growth, you may feel it necessary to take action. Regularly blasting off with a hose or wiping away with a cloth or piece of kitchen paper can help to keep numbers down without harming other members of the ecosystem.