ON CUTTING DOWN PERENNIALS
Now that we have gone well past the period of garden history when herbaceous plants were cut back on a particular date in autumn, regardless of what they looked like, we have to make this decision ourselves. It is a decision that many gardeners seem to find difficult to take. Piet Oudolf has been asked it many times, and he tells me that the always tells people that only they can make the decision – “you do it when you want to” he says. Which is not actually what they want to know. They want to be told. As if there is a right time and a wrong time. As in the old-school gardening when there was always a right way and a wrong way. But isn’t it better to make your own decisions? Based on what you feel is right for your garden.
The only parameters are: 1) for seeds for wildlife and for some hope of the dead remains looking attractive it is good to leave stems standing for as long as possible, 2) they have to be cut down before the first bulbs begin to emerge, as otherwise you will squash the bulbs with your big feet.
What I usually do (is this any help?) is to cut down everything which looks a mess at the end of November and the remainder (grasses, very strong perennials like eupatoriums) in January. But the weather is the deciding factor. This year we had an early snowfall in November. Not much, but that classically English very wet and heavy snow which crushes almost everything, including miscanthus and eupatorium. The fine dry snow which inhabitants of Mitteleuropa and North America get and which drifts in between the stronger stems and looks very picturesque is quite alien to us. As a consequence practically everything has to end on the compost heap.
Which brings me to the next set of questions. How do you cut it all down and compost it?
Secateurs and shears can be surprisingly quick. Low clumps of leafy soft material can be cut through with a sharp sickle. For larger plantings where there are no labels the strimmer/brushcutter can be used. This is apparently what is done in the herbaceous plantings of Enkjöping in Sweden. The idea is to strim everything down to form a mulch – no need for carting away and composting. Great, but the very stout stems, almost woody in their hardness – some helianthus, vernonia (not called ‘ironweed’ for nothing and miscanthus, will only be scratched by a strimmer’s nylon cord. They can be cut down with a metal brushcutter attachment but not effectively strimmed unless you have lots of patience and strength (I have neither).
However you cut, you will be left with lots of material. Perhaps, if you have been an ambitious layer-outer of big borders, a rather intimidating amount of material. In my last garden I really did not have the space to effectively compost it, or at least to turn the resulting (vast) heap. Cutting thicker stems up to make them rot down more quickly helps – if you do, not the chances are that there will still be a pile of dry stems a year from now when you do the next annual cut. Some use a shredder. But shredders are designed primarily for woody material and many makes simply clog with softer herbaceous material. And anyway, they it can be a very slow process shredding a large prairie border.
My solution is actually to separate the material into 1) soft and/or easily cut and 2) recalcitrant near-woody. The former can be piled into a conventional compost heap, the latter stacked in an out of the way corner to rot down more slowly, or shredded/used as mulch. Or burnt. The stacking/slow composting route probably makes a good wildlife habitat in the same way that a pile of rotting logs does. The latter is more fun. Bonfires are a bit politically-incorrect these days, but a good burn up makes a fine centrepiece for a family evening. I haven’t done this yet, but the real American prairie types would probably burn in situ. More fun. Slightly scary. Actually very good for weed control (Sheffield University research) I’ll let you know when I do.