By skyforbes 
Bupleurum rotundifolium ‘Grifitthii’ is one of those useful foliage plants that once you have you feel you can’t be without – and in fact, happily, you won’t, as it self seeds everywhere from year to year if it is given a space it likes in full sun in well-drained soil. It’s like a euphorbia but without the white sap, with loose umbels of acid green flowers that grow ‘through’ the rounded leaves. It’s not a classic flowery flower, but it’s incredibly useful for cutting, and lightens up a dense border with an injection of fresh green. Growing 50-90cm tall, it has a tendency to flop like a gawky teenager, and needs a home among other mid-height perennials or grasses to give it some framework and support. It looks particularly good with dark blue salvias and perhaps with a grass or two thrown in too – Stipa tenuissima or Pennisetum ‘Hameln’.
Growing bupleurum couldn’t be easier in well-drained soil. The wild form – now quite rare – was in the past an arable weed on chalk or limestone, which explains why it grows so well in my Oxfordshire garden. It is very hardy so can be sown in early spring – March or April – direct into the soil where you want it to flower. If you want back-up, sow a few seeds in modules, so that the plug plant can be moved and planted out without disturbing the roots when large enough. As a postscript it’s worth mentioning a couple of other bupleurums, although they aren’t annuals: B. longifolium ‘Bronze Beauty’ is a perennial with yellowy-green umbels that turn a beautiful coppery bronze in autumn, while B. fruticosum is an evergreen shrub with hard, bobbly flowerheads that are attractive in a different way.