Native plants are of course plants that are believed or known to have existed in this country and the British Isles for hundreds if not thousands of years.
There are not any rules about having native plants in your garden for producing the best type of nectar. In fact Marina say there are thousands of great plants to choose from that produce excellent levels of nectar and they do not all originated from in the British Isles.
Buddleja is one such non-native plant that many garden lovers have in their garden which has proven year on year to produce great levels of nectar, providing food for loads of insects and butterflies. Buddleja is known as the Butterfly Bush in fact.
Of course there exist great native plants too, native woody plants (for example trees and shrubs) provide support for a large amount of insects that then provide a fantastic food source for a large number of animals.
It is said that animals do not discriminate between native and non-native plants for food, so it is entirely up to you whether you choose to plant and grow native or non-native plants. It is recommended that you still choose plants that offer great colour, shape, nectar-richness and berries, so that you will still attract a large amount of wildlife to your garden.