Roses on their own can look wonderful and, for much of the twentieth century, this is how most gardeners planted them – in formal rose gardens. These now though are a rare sight and roses are much more commonly seen mixed up with other plants where the final effect can be wonderful. The other plants are traditionally perennials but in fact annuals and biennials will make excellent companions too.
The advantage of mixing roses up with other plants is not just visual there are great health benefits too. Pure rose gardens are monocultures and all monocultures are very good news for pests and diseases. A mixed border will confuse the pest making them less likely to lay their eggs and it will attract in more beneficial insects that will delight in feasting on the aphids. Diseases too will find it more difficult to spread around; the spores are more likely to drop on the wrong host.
The more informal, shrubby roses look best in mixed borders, groups like David Austin’s English Roses, the Old Roses, Hybrid Musks, Rugosas and the rather vaguely named Modern shrub roses that include the likes of Rosa ‘Bonica’ and Rosa ‘Ballerina’. Some of the Floribunda roses can look good as long as they are not too brightly coloured. I don’t think the Hybrid Teas work well with their stiff upright growth and very stylised flowers. Depending on the size of your border you might want to consider planting both the roses and perennials in bold groups being sure to space both of them quite closely so that the final effect of each group is of one large plant rather than a number of individuals.
Almost any type of perennial, annual or biennial looks good with roses but I tend to favour the wilder, less highly bred varieties as I think they look better and they are more likely to attract in the beneficials. Flowering time is important, the beautiful effect is achieved when the two are flowering together not when they miss each other by a few weeks. The great advantage of roses is that most repeat flower and so it is fairly easy to find suitable companions.
There is a huge list of suitable plants but here are some of my favourites. Gaura lindheimeri (that flowers over a long period), Hesperis matronalis (Sweet Rocket – a very lovely and very fragrant plant), Digitalis (the foxgloves and not just the common one there are some very beautiful species like Digitalis ferruginea and Digitalis lanata), Cosmos (the tall Cosmos bipinnatus the most often seen one with white or pink flowers and the shorter Cosmos sulphureus with yellow or orange flowers) and Ammi major (a very lovely plant with umbels of flowers).
Any plant with blue flowers are particularly useful as there are, of course, no true blue roses and this colour goes so well with all of them. Particularly good are various asters (like Aster x frikartii ‘Monch’), delphiniums, eryngium, hardy geraniums (cranesbill), nepeta (catmint), Phacelia tanacetifolia and echium (the last three are great favourites of mine as they are very pretty and particularly attractive to insects).
The golden rule is to never allow the companions to grow right round the base of the roses. Roses love plenty of moisture at the roots and need their fair share of nutrients to grow and flower well so keep them far enough away that they don’t compete. Although not so far apart that you don’t get the flowers nestling up to each other and creating a beautiful show.