Naturalistic garden design is in a sense a contradiction in terms. But it is possible to design using natural processes and a deliberate approach to chance.
 I was struck by this attractive combination in the garden this morning: the Forget-me-not blue flowers of Green Alkanet (Pentaglottis sempervirens), the nodding white bells of Symphytum Hidcote and the pink veined flowers of Geranium x oxonianum.
 Some gardeners will tell you that Green Alkanet is an invasive self-seeder, that Hidcote comfrey is too rampant, that G. x oxonianum spreads untidily. True, they're not appropriate if you want borders of bare earth containing a few well behaved perennials.
 But I let Alkanet do its thing in parts of the garden. I chose the comfrey for its groundcovering qualities. There were a few clumps of the Geranium when I moved here and I've allowed them to multiply. They intermingle and with a bit of light maintenance get along fine with each other.
 I note that these unruly characters are magnets for bees. It's reckoned that angiosperms (flowering plants) and bees have co-evolved on a timescale of well over a hundred million years. Nature is a good designer.