I don't presently have access to garden space (I just grow English ivy in a couple of indoor pots, to which a native grass, a fern, and moss have also colonised, by chance), but I remain interested and sure that native gardening is a good green way-forward...

Green/eco-friendly gardening is native gardening, and vegetables, plus other consumables, should be the only exotic-flora we plant - as doing so can help limit food-miles, etc. By filling our other garden spaces with natives, we use less water and other resources, whilst aiding the native-fauna that, over the centuries, evolved with them. (Even high-nectar exotics, such as Buddleia, that are very attractive to SOME native-fauna, should be avoided, because they upset nature's/God's balance – God created evolution, too, that is.)

Our green gardens, with their vegies and natives, can be made still greener by the addition of compost heaps/bins; a wildlife pond – for native frogs, newts, and so on, rather than exotic goldfish; bee- and bird-boxes, plus carefully-selected feeders; rain- and grey-water vats; by growing everything organically - including thrifty home-propagation plus species-swapping; and by leaving some lush untidy patches, decaying branches, etc. (from here).