In article , Camilla
Peake writes
Can anyone inform me what the black sticky substance might be that keeps
appearing on my bay trees. They are outside in Summer and in an unheated
conservatory in the Winter. It drops down onto the floor tiles around the
pots.
Have tried washing with mild soapy water but, alas, it keeps returning.

It's mould growing on the excretions from sap sucking pests.

Possible candidates are aphids, though the soapy water should have seen
to them, or scale insect. You would spot the scale insects as small oval
brown scales on the undersides of the leaves along the veins. Difficult
to get rid of because of their tough coats - I remove them by hand but
on a bay tree of any size that is impractical. Otherwise use a systemic
insecticide.


--
Kay Easton

Edward's earthworm page:
http://www.scarboro.demon.co.uk/garden/