Pursuing native plants when gardening will only help to encourage the native species which seem to be fast disappearing. This is not to say that gardens can't be without exotic or colourful foreign friends, but incorporating a mix will help to enhance the garden and be of benefit to the overall well-being of our surroundings.
Building a willow den for example could help to manage boggy areas while at the same time providing kids with a place to play. It doesn't have to be a den. Sculptures of all sorts can be designed and not just with willow. Hazel is another tree well suited to simple propagation - and will provide you with nuts if the squirrels don't get there first!