The Golden Rule: Old Wood vs. New Wood
Before you pick up the shears, the most important question to ask is: does this plant bloom on old wood or new wood? This single detail determines the right time to prune. Plants that bloom on “old wood” form their flower buds on last year’s stems. If
you prune them in late summer or autumn, you are literally cutting off next spring's flowers before they have a chance to grow. Conversely, plants that bloom on “new wood” produce flowers on the growth they make in the current season. Pruning these before they start growing in spring, or lightly trimming them in summer, can actually encourage more blooms.
Hands Off: Plants That Bloom on Old Wood
These are typically the plants that burst into flower early in the spring. They use the energy stored from the previous year to produce their spectacular, but often brief, display. Think of shrubs like Forsythia, Lilac, and certain types of Hydrangeas. For these plants, the only safe time to prune is within a few weeks after they have finished flowering. This gives them the rest of the growing season to produce the stems that will carry next year's buds. If you prune them now in August, you won’t kill the plant, but you will be rewarded with a lot of green leaves and zero flowers next season. The best approach for these plants in August is to simply leave them alone, aside from removing any clearly dead or diseased branches.
Green Light: Plants to Prune in August
August is the perfect time for a strategic trim on many summer-flowering shrubs that bloom on new wood. Many popular Indian garden staples fall into this category. After their main flowering cycle, a light prune can encourage a second flush of colour and prevent them from becoming leggy. Plants like Hibiscus and Bougainvillea respond well to this treatment. For roses, deadheading spent flowers and lightly shaping the plant encourages it to produce more buds instead of putting energy into seed production. A summer trim on Wisteria, cutting back the long, non-flowering shoots, helps control its vigorous growth and encourages the formation of flower spurs for next spring.
A Guide to Common Garden Favourites
To make it simpler, here’s a quick guide. Go ahead and prune these in August: Roses (deadhead and light shaping), Bougainvillea (trim after a bloom cycle to shape), Hibiscus (lightly prune to encourage bushiness), Lavender (cut back faded flower spikes), and many perennial herbs like Basil and Mint to encourage fuller growth. Be cautious with these: Spring-flowering shrubs like Azalea and Rhododendron, which have already set their buds for next year. Also, avoid heavy pruning on most fruit trees; while summer pruning can be used to control size, it reduces the plant's energy production and is best done with a specific goal in mind.
The Right Way to Make the Cut
Once you’ve identified the right plants, technique matters. Always use sharp, clean tools to make a clean cut, which helps the plant heal faster and prevents the spread of disease. When trimming shrubs like roses or hibiscus, make your cut at a 45-degree angle about a quarter-inch above an outward-facing bud. This directs new growth away from the center of the plant, improving air circulation and reducing the risk of fungal issues. For plants you're trimming back, like lavender, avoid cutting into the old, hard wood, as it may not regrow. The goal of August pruning is refinement, not a radical overhaul. It’s about working with the plant’s natural cycle to guide its energy effectively.
