If your plant is a herbaceaous perennial it will naturally lose its leaves at the end of autumn. If however, your plant is losing leaves during it’s peak performance months, this could be due to a number of issues. Over or underwatering can cause plants to drop their leaves. As can pests like aphids and certain types of beetle like the vine weevil. Inspect your plants carefully to see if there are any obvious signs of pests. Vine weevils look like black beetles, the length of a thumbnail. Their larvae do the damage to the plant’s roots. Nematodes are a good way to kill them and you can buy these online and get them posted to you. Aphids can be squashed using your fingers or hosed off with water. Soap mixtures can also be sprayed onto the leaves to kill off aphids, but at Muddy Trowel, we have found that this can sometimes caouse powdery mildew in hot and humid conditions, so keep an eye on your plants following this treatment.