Herbs are often seen as the easiest plants to grow, as they can even thrive on a kitchen windowsill, but a common mistake is feeding them all the same fertiliser. Most plants need to be fertilised in summer to encourage them to grow stronger, as leafy herbs such as basil, mint, or parsley will grow tastier leaves if fed now.
However, woody herbs like lavender or rosemary naturally come from dry climates and will grow better in poor soil that does not have much nutrients. Feeding Mediterranean herbs in late July or early August will cause their flowers or leaves to drop and encourage soft leggy stems that will attract pests like slugs.
The stress of the fertiliser can also stress woody herbs out and make it less likely they will survive in autumn, as their new weak stems will become damaged in cold weather.
Instead, Amanda MacArthur, an expert from the Food Gardening Network, has shared a simple way to help lavender and rosemary grow is to add gravel to their soil in summer.
Amanda said: “This may not be the first thing you think of as mulch, but herbs like rosemary that come from Mediterranean climates love the drainage and the heat that gravel offers.
“And since gravel isn’t going to decompose, it’s a good choice if your herb garden is also part of your landscape design.”
Mulching is a simple gardening technique of adding material around a plant to help protect it. In summer, plants are usually mulched with a substance like bark to keep more water in the soil.
However, both lavender and rosemary dislike moist soil, as it makes them more prone to root rot and other fungal diseases caused by excess water.
Adding gravel helps water drain quickly and reflects sunlight, which warms the soil and recreates the dry, rocky conditions these herbs naturally prefer.
This creates a healthier, more resilient environment that encourages stronger roots, sturdier leaves, and better flower production.
It also boosts essential oil levels, making lavender flowers more fragrant and rosemary leaves richer, more intensely flavoured.
Whether you grow woody herbs in pots or the garden, adding a little gravel can make a big difference to help lavender and rosemary thrive in summer.