So that you can become aware of the worst culprits here is a 'rogues gallery' of the 5 banned aquatic plant species highlighted by DEFRA and the 'Beplantwise' campaign. Since April 2014 these are banned from resale in the UK but you may already have some of these in your pond.
This month the cutting back and cleaning up of the pond begins as the weather cools down and it is important to deal with unwanted plants carefully.
Composting them is the best method and never throw your surplus into local ponds or waterways.
You may be throwing away a plant that is a banned aquatic species that could quickly become an invasive non-native pest that will block the waterways or starve out British species of plants or wildlife.
Preventing the spread of invasive non native aquatic plant species is highlighted in a second DEFRA campaign to Check, Clean and Dry –
1. Check your equipment, footwear and clothing for living organisms.
2. Clean and wash all equipment, footwear and clothing near the water body that you have been at.
3. Dry all equipment, footwear and clothing and don’t transfer any water elsewhere.
For your information: Water Hyacinth and Elodea crispa are on a list from DEFRA of plants to be avoided with a view to them being removed from sale in a few years time.