One possibility is Lantana's ideally likes sand and clay loam but it will be fine in most soils but needs good drainage as Lantana will not do well with over watering or soggy conditions. Could you have over watered it?

hi Drc726 my lantana is in a pot. it is a standard plant and some of the buds R going black 2. ill stop watering it 4 a few days.as iv been watering it every day as it is in my conservetry. cheers colin.

Hope that it works Colin good luck Denise.