Gardening tips: Learn which plants to prune and which to let grow this month, according to our in-house horticulturist's advice
In the heart of summer, it's essential to maintain the health and beauty of your garden. While some plants thrive with a little summer pruning, others should be left untouched. Here's a guide to help you navigate through the dos and don'ts of summer pruning.
August is the perfect time to prune key plants for longer flowering and preparation for seasons ahead. Plants like goldenrod (Solidago) benefit from a trim, with the tops being removed, leaving the foliage for an evergreen coverage. This practice helps control the spread of seeds and encourages new growth.
However, there are plants that should generally not be pruned in summer. Lilacs, oaks, rhododendrons, birches, and maples are among them. Pruning these plants in summer can lead to the removal of next year’s flowers, delay recovery for multiple seasons, or weaken the plants due to sap bleeding.
Lilacs and rhododendrons form their flower buds shortly after blooming, so pruning them in summer removes next year’s flowers and can delay recovery for multiple seasons [1]. Oak trees are vulnerable to oak wilt, a fungal disease spread by beetles attracted to fresh summer pruning cuts; they should be pruned in winter when beetle activity is low [1]. Birches and maples are heavy sap bleeders and cutting them in summer can severely weaken them and damage their ornamental branch structure; pruning these is best done in late winter or early spring when dormant [3].
Woody deciduous trees are generally not recommended to be pruned in late summer because the new growth stimulated does not harden off before freezing temperatures, leading to winter dieback.
In contrast, some plants like yarrow benefit from light summer pruning to encourage more blooms and improve air circulation [1][4].
Poppies (Papaver spp.) are another interesting case. They should not be cut back in August. Instead, they add architectural quality to flowerbeds and disperse seeds naturally. Leaving the flowers encourages the growth of lovely hips, beneficial for wildlife.
Nepeta (Catmint), on the other hand, should not be pruned back this month. Leaving Nepeta provides nectar for pollinators and serves as habitat for insects and wildlife over winter.
For those seeking advice on plants to cut back in August and those to leave alone, Orpheus, a professional gardener, designer, and lifelong plant enthusiast, has provided valuable insights. Orpheus shares helpful gardening tips and videos on Instagram @our website.
Foxgloves (Digitalis) should be deadheaded in August, going all the way down to the base of the stem and removing dead foliage. Deadheading other roses promotes new growth for blooms year after year.
Lastly, goldenrod (Solidago) can be cut back in August to prevent seeds from spreading too vigorously. Alchemilla Mollis can be cut back this month, down to the ground.
Remember, timing is crucial when pruning plants. By following this guide, you can avoid common summer gardening mistakes and ensure the health and beauty of your garden for years to come. Happy pruning!
[1] RHS (2021) Pruning Advice for Summer. Available at: https://www.rhs.org.uk/advice/profile?PID=325 [2] HGTV (2021) Pruning 101: What, When, and How. Available at: https://www.hgtv.com/design/outdoors/gardens/pruning-101-what-when-and-how [3] The Spruce (2021) Pruning Birch Trees. Available at: https://www.thespruce.com/pruning-birch-trees-3158468 [4] Garden Myths (2021) Pruning Yarrow. Available at: https://www.gardenmyths.com/myths/pruning-yarrow/
- Pruning key plants like goldenrod in August can help control their seed spread and encourage new growth.
- Conversely, pruning plants such as lilacs, oaks, rhododendrons, birches, and maples during summer is generally not recommended, as it may result in the removal of next year’s flowers, delayed recovery, or weakened plants.
- For plants like yarrow and poppies, light summer pruning can benefit their blooming and overall health while providing wildlife habitats and encouraging natural seed dispersal.
- When it comes to plants that should not be pruned in August, caring for Nepeta by letting it remain for nectar sources and habitats for insects and wildlife over winter, and leaving foxgloves to deadhead and remove dead foliage to promote continuous blooming in subsequent years.
