Sticky situations

Sticky leaves are a common problem, but make sure you remove the cause and clean in the right way, says Bob

- Bob Flowerdew

STICKY leaves are real giveaways on houseplants and in the greenhouse, especially at this time of year. Likewise, outdoors almost all plants (even whole gardens) can become sticky, particularly if underneath a lime tree. It is almost certainly a sign of critters – either higher up on the plant or on another overhead – sucking sap in vast quantities.

Sap is not designed for insects but for plants. Thus, most sap-suckers (which don’t suck but just pierce cell walls when sap pressure pushes it into them) do not want the watery sugary part, so after taking their needs it shoots straight through them. This then falls on everything below and nearby. Some other critters, including bees, wasps and butterflies, consume this ‘honeydew’ – but much just turns black with mould.