Went along to the South London Botanical Institute yesterday to do a bit of botanical gardening. The garden contains an interesting mix of native plants and 'exotics'. For example a Chusun palm (Trachycarpus fortunei) rubs shoulders with a couple of UK wildflowers by the pond.
Marsh Mallow (Althea officinalis) has been used for various edible and herbal preparations over the centuries- needless to say that includes the original recipe for marshmallow.
Purple Loosestrife (Lythrum salicaria) is another beautiful wildflower that likes to be near water. It causes no problems here in its natural habitat but is considered extremely invasive in the States.