Not all plants (and I am talking about bulbs and perennials) die back at the same time. Spring flowering bulbs have generally died back by early June, leaving a space for burgeoning summer growth to fill. Allium foliage has a tendency to start decaying just as the bulbs come into bloom – I find that planting them among other things that are low at this time disguises this untimely decay. But what about perennials that die back before autumn, leaving an unsightly space in the border – lupins, oriental poppies or eremurus, the foxtail lilies? For these, we need something that takes its time to get going but then rapidly takes over the recently vacated space.
I find some of the stipas, evergreen grasses, are useful in this role. I cut them down just as new growth is about to start in early spring; they soon show green shoots but only start to accelerate in the second half of May. The well-known stipa tenuissima is invaluable for filling small gaps.
But for larger spaces, something meatier is required. I was intending to recommend another member of the same family, stipa ichu, but those pesky taxonomists have been working overtime again, and we must now call it jarava ichu.
The Peruvian feather grass, to give it its common name, needs a warm, sunny spot in well-drained soil, when it will reach three to four feet. According to the Knoll Gardens website, it makes “bright mounds of green foliage topped with long shimmering silvery white panicles of flower during summer,” while Great Dixter makes mention of “showy flower heads.”
Under this specimen are half a dozen eremurus, waiting their turn next year. If you have the odd pet alpaca or llama, they will thank you as this is their natural food source. Another plus is that, unlike its cousin S. tenuissima, you are not going to be pulling up large numbers of seedlings. Filling gaps is not only keeping the garden’s appearance going, it allows you to grow more plants (and what keen gardener doesn’t want to do that?)