Somehow when herbs come to mind, we think of small bushy plants like thyme, but rosemary is not like that. It forms a large straggly bush with more sprigs of leaves than any cook is likely to ever need, but rosemary has a second role, that of ornamental shrub.
It is a very pungent herb, both in terms of scent and taste. Its tough little leaves are filled with volatile chemicals that are released when the leaves are crushed, even when the plant is just brushed against and, on a warm day in summer, these odour chemicals are released into the air and the scent can be picked up at a distance.
Native to the Mediterranean region, rosemary joins other plants from that region as culinary herbs: thyme, sage and marjoram among them. These three are of the same family, the sage family or the mint family, which contains plants noted for their scent, including the most notable of the lot, namely lavender.
Like lavender, rosemary is well adapted for the dry summer weather and baking heat of Mediterranean hills, and they have evolved similar strategies for survival. Both have narrow, hard evergreen leaves, partly rolled up to reduce moisture loss to the dry air. Both form low, dense bushes that grow fast, colonising empty ground. Both plants thrive in poor well-drained soil and tend to be short-lived in heavy soil, especially if wet in winter.
Rosemary is at home on a dry bank, especially if the soil is sandy, and its somewhat straggling growth is good for spreading over rocks and to hang over a retaining wall. There is a prostrate version that does not just spread out but lies flat on the soil surface and effectively flows downhill. There are also upright forms, such as 'Jessop's Upright', with upright spiked stems. There is some variation in colour too, dark or lighter blue, almost white sometimes. 'Tuscan Blue' is upright with deep blue flowers.
The flowers appear early, often in late winter, and although they are not very large, they have value so early in the year. The main flowering is in spring and early summer. Quite often, especially in a mild area and after a warm sunny summer, a scattering of flowers appears on the new growth in autumn.
Rosemary is easily pruned after flowering, cutting back the green shoots to within 10 centimetres of where they arise. The best policy is to cut it back a little each summer just after flowering.