Written by Mike Swan
As a contribution to Flood Action Week, Defra and Floods Minister Emma Hardy are urging us to cultivate flood-resilient plants in our gardens, and on 17th October The Independent brings us the story; “Homeowners urged to use five key plants to make gardens flood ready”.
Living well above the spring line in chalk country, means my garden is pretty much automatically ‘flood ready’, apart from possible runoff to our winterbourne. But my curiosity was aroused, so I read on.
Surprise, surprise, one of Defra’s five was included in what I already grow. Red bistort (Bistorta amplexicaulis) was here when we arrived in 1993, and we would have struggled to eradicate it even if we wanted to. Its attractive red spikes are great for cut flower arrangements, but it is quite invasive and needs keeping in check. It may also like moist soils, but I can vouch for the fact that it does just fine on dry chalk, and yes the bumblebees like the flowers too.
So, what of Defra’s other four? They are River Birch (Betula nigra), Red Twig Dogwood (Cornus sericea), Mace Sedge (Carex grayi) and good old Yellow Flag (Iris pseudacorus).
Now yellow flag is one of my favourite plants; in full flower on the river bank at Mayfly time, it is redolent of the moment that spring turns into summer, and a joy to behold. It needs wet soil, but I have to confess that I fail to understand how it would help to make a garden ‘flood ready’, although I suppose its roots might help to stabilize the banks and reduce erosion if yours includes a river or stream.
The rest may also have helpful credentials and I guess that mace sedge could help to trap soil run off if your garden goes under. We are also told that these plants will soak up water like sponges, although I’m not sure if that helps much in the event of a real flood. On the other hand, a thicket of dogwood will soon shade out lower ground cover and if anything increase soil erosion risk. The same also applies to a quick growing birch, with the added risk that the neighbours might not like it if you cut off their sunshine.
What struck me more immediately was that I did not recognise the scientific names of most of these plants. My history in studying native plants and their pollination goes back five decades, and scientific nomenclature moves on, so I thought I might be out of date. But no, when I looked them up, I discovered that that River Birch, Red Twig Dogwood, and Mace Sedge are all North American. I knew that Red Bistort was a garden plant and almost certainly a foreigner; in fact, comes from Himalaya.
So what goes on here? On the one hand, Defra urges us to nurture native flora and fauna, and on the other, it suggests we fill our gardens with non-natives to help reduce flood risk. There are plenty of native sedges that like damp soils, and would do just the same job as C. grayi. Meanwhile, the native Red Dogwood (Cornus sanguinea) would surely be just as effective as the American, and has equally attractive red stems to give colour in winter,. Againwe have two native birches (B.pendula and B. pubescens) that would surely do the same job as River Birch!
Come on Defra, lets have some joined up thinking here.