Pruning in May with Arit Anderson
Keep vigorous lilac from growing too tall by pruning after flowering – Arit Anderson shows you how
What is it about the month of May that gives joy to the soul when we look at our gardens? Is it the flush of verdant leaves or the peonies, spireas and purple haze of ceanothus, all vying to catch our attention? With the warmer temperatures and extra light comes new growth, and there are several plants that will benefit from being pruned now. But before you get started, check for active birds’ nests and delay pruning if you find any.
Early flowering shrubs bloom on last year’s stems. By pruning them now, this year’s stems will have enough time to mature so they’re ready for flowering next spring. Lilac is best pruned as soon as its flowers fade, to deadhead it and improve its shape. By doing this now you’re less likely to remove the buds for next year’s flowers, which may happen if left later in the season. Evergreen hedges, such as box, can be trimmed towards the end of May, and evergreen shrubs will prosper if you remove all the dead, damaged and diseased shoots. But do wait until all risk of frost has passed in your area.
Discover Arit's pruning advice for May, below, including her step-by-step guide to giving lilac bushes a trim.
Plants to prune now:
May is a busy month in the garden, but it’s well worth making time to prune plants that will really benefit, and you’ll reap the rewards next year.
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Just remove any frost damage from this evergreen shrub and cut back the sideshoots to enhance the overall shape of Choisya.
After flowering , vigorous Akebia quinata can be pruned to keep it within the available space by removing the longer shoots.
Pruning now gives the shoots time to harden off. Aim to reduce its height and density, so more light and air can get into the bush.
Thin out congested growth and remove any rogue branches from hibiscus that are making the overall shape unbalanced.
It’s easy to get overzealous with the loppers, but pruning plants at the wrong time may remove this year’s flowers or cause other damage. Here are some plants to leave unpruned now:
- Sambucus: If you prune elder now, you’ll cut off the flower stems before they have a chance to bloom. Instead, prune when dormant in late winter.
- Prunus serrula: Wait until midsummer if you need to cut back Tibetan cherry, as pruning too early may cause bark dieback, especially on established trees.
- Chimonathus: Wintersweet should only be given a light prune in late winter after flowering. Hard pruning can stop it flowering for several years.
Step-by-step: Pruning lilac
Lilac is a wonderful garden shrub with beautiful fragrant flowers. But if left unpruned, the older stems grow tall, producing fewer and smaller blooms high up, where their scent can’t be appreciated. Cutting lilac back annually after flowering will create a strong framework, from which fresh stems will sprout, and these will carry abundant flowers low enough to enjoy. It’s important to deadhead after flowering, down to two new shoots, so that over the summer there is time for young flower buds to emerge, ready for next spring.
Assess your shrub first, so you can identify any dead, damaged or diseased stems that need to be removed first. If their thickness is less than 1cm, use secateurs, but for anything larger use loppers
Open up the centre of the plant, removing congested or inward-facing stems. This will keep air flowing through the plant, which reduces airborne disease and allows you to see any pests more easily.
Remove any crossing stems. These tend to rub against each other, creating wounds that can be an entry point for disease. Long-handled loppers are handy for reaching into tight spaces.
Finish by cutting off any smaller dead twigs and removing any remaining faded flowerheads to tidy up the plant. Deadheading prevents the shrub wasting energy on producing seeds.
Other plants to prune this way:
Several other popular shrubs can be given similar treatment at this time of year. Weigela, once established, can be pruned annually after flowering, but be mindful to follow the habit and shape of the shrub. Flowering currants (Ribes) respond well to annual pruning to encourage abundant blossom and keep them vigorous. After the last flowers have faded, prune immediately, removing one in three stems, taking the oldest first.