I feel confused between laurels and cherries and plums, and the position of their extra-floral nectaries.

Point 2.23 of the guidance notes requires us to be able to describe the extra-floral nectaries of cherry laurel, cherry and plum - all three are Prunus species. Celia Davis says that in some cherries (Prunus spp) the extra-floral nectaries are on the petioles, but it seems that the extra-floral nectaries of Cherry laurel (also a Prunus - Prunus laurocerasus) are on the underside of the leaf as in the case of Laurel (Laurus nobilis).

So, do some Prunus species have extra-floral nectaries on petioles and others have them on leaves? And what about plums then? I can't find any information about their extra-floral nectaries.

Kitta