What can be killing off my plants?
over the 18 months that we've been in this house, plants in the garden have been randomly dying off. At first I thought that they were getting too wet as it is quite a damp garden - it's actually an enclosed patio that seems to really hold on to water on the ground. But the latest one to go is my beloved Houttuynia cordata, which I bought specifically because it likes damp or boggy ground.
The plant looks perfectly healthy, and then overnight a number of the leaves will turn brown, quickly followed by the rest of the plant.
I asked a neighbour who gardens what she suggested, and she said she didn't know but that it was happening in her garden too, and in others in the local area. She thought it might be root beetle but when we pulled the dead plants up the roots were fine.
So far it's taken her monkey puzzle tree, a small confer I had, my three cosmos - one by one, although they were all in the same pot - and some rosemary and other herbs, so quite a range of plants.
All of mine are in containers with fresh soil, so it can't be transmitted through the soil. Any ideas?