Behind the pergola in the Hilltop Garden, the border sits in partial shade with a large hornbeam hedge a couple of metres in. It's had the normal yearly maintenance from us - just cutting back and adding tender plants for the summer months. The hedge has always demanded more moisture than the bed can offer and subsequently some of the plants perform poorly. There's a rain shadow from the wisteria on the pergola and it's the trickiest space to put any sprinkler without soaking unsuspecting visitors as they stroll through to look at the pond!
The border has also been overrun with Japanese anemone and hairy chervil, Chaerophyllum hirsutum ‘Roseum’. These thuggish plants colonise easily, either seeding or rooting everywhere. They look great for a couple of months and then sit, fade to a pale yellow and take up space that more attractive species could have a chance in.
Our plan then is firstly to dig as deep as possible to break up the dry clay soil that's compacted badly over the last few years. Then we'll add a thick, six inch layer of our own compost and dig it in as much as possible. There's already plenty of grit from when it was previously cultivated. The key with clay soils is to break up the particles of soil that stick together in wet weather and crack open in the summer months. The addition of grit and compost will achieve this. An improved structure will make a better display as plants don’t struggle to get their roots down quite so much.
I've picked some new plants which tolerate drier situations with some shade and a hedge to compete with. Also they must suit intermingling with ferns, a couple of shrubs and a small apple tree.
We've chosen a hollyhock, Alcea rosea ‘Crème de Cassis’ that will be tall for the back, seed around and not mind the challenging conditions; Verbascum phoenicium ‘Rosetta’, a shorter variety at 60cm (2ft) further forwards; foxgloves, Digitalis ‘Camelot Rose’ to seed around the shadier areas and Lupinus ‘The Chatelaine’ to flower early and be cut back, not minding the dryness later on. There will also be a selection of cornflowers, geraniums and snapdragons.
Along with the ferns, bulbs, Japanese anemones and of course the tender perennials added in May, this look will be simple but pretty and be assisted by the addition of organic matter. In spring when we plant, it will of course need watering in to aid establishment. Leaky hose will assist us here, but this is only good on small areas where not much digging or splitting and dividing will happen in the future as it has a habit of being sliced through, punctured and squashed. It drives us horticulturists crazy trying to fix it!
Hopefully this will do the trick and we just have to wait now to see what summer brings. I may have to bulk up the existing bulbs as we didn’t find many whilst digging, but I’ll wait to see what appears first this spring before tackling that point.
Hilltop Garden, RHS Garden Hyde Hall, Essex
Improving clay soils
Irrigating your garden