Pruning is a crucial gardening job throughout the year to help keep the garden neat and tidy.
It can also help encourage both strong and new growth, which is ideal if you want plants to return year after year.
William Mitchell of Sutton Manor Nursery told Express.co.uk: “The best time to prune is around five or six weeks before the first frost is due.
“This means that the best time to prune lavender is between September and October.”
Left to grow on its own without being pruned, lavender can become bushy and leggy.
This not only looks messy, but it can also affect the growth of the plant the year after.
The expert added: “It is good to prune lavender around this time so that the pruned areas of the lavender plant have a good amount of time to become established before the harder weather comes in.
“When pruning lavender, you should simply trim a third of the plant’s growth from the flowering season over summer.
“Try not to cut back too far though as it could make them susceptible to frosts over the winter months.”
According to the Royal Horticultural Society (RHS), foliage can be clipped over spring if growth is untidy or frost-damaged.
The experts said: “Lavender does not break new growth easily from old stems so don’t cut back into the woody stems.
“Even if pruned annually, older lavender plants can become straggly, very woody and misshapen so, as they are fast growing and established quickly, they are best replaced if you want to keep everything looking neat.”
If gardeners forget to prune their plants during the autumn months, wait until the following spring to give them a haircut.
Judith Hann, author of Herbs, explained: “The normal advice is to replace plants when they become leggy, usually after three to five years. But I avoid having to do this by cutting right back into the wood.
“I have not lost a lavender plant yet in the 20 years they have been growing in my garden.”
Although not often recommended by experts, it can be a good way to encourage lavender to grow.
Gardeners should make sure their lavenders are getting enough water throughout the autumnal months, but not too much that they are swimming in it.
Lavenders generally don’t require a huge amount of water in order for them to thrive.