The white rose of Scotland was on everyone's lips during the state opening of Parliament last month, when the 56 newly elected SNP MPs wore them in button holes, a timely reminder that the Scots rose has a long history.

Back in the 11th century, during the reign of Malcolm II, the white rose was the badge of the Keith clan. The rose is also linked to David I, Robert the Bruce and Bonnie Prince Charlie. Much more recently, Hugh McDiarmid wrote in his poem The Little White Rose: "The rose of the world is not for me/ I want for my part/ Only the little white rose of Scotland./ That smells sharp and sweet - and breaks my heart."

Like most species roses, this ancient Rosa pimpinellifolia will soon dazzle with its wonderful brief blaze of flowers. And it pays to keep them healthy throughout the season.

Whether your roses flower once or repeat, rose blackspot, powdery mildew and greenfly attack cause most damage. Although they can't be completely prevented, some precautions minimise the risk. Unlike many modern cultivars, pimpinellifolias don't have blackspot resistance, but fare better when roots are kept cool and moist.

In spring, cover the soil with a mulch while it is still moist. Spray the leaves with liquid seaweed to help keep disease at bay and an application of two teaspoonfuls of bicarbonate of soda per half litre of water may help when blackspot first appears. Clear away and dispose of all fallen leaves and cut out diseased stems and branches.

Powdery mildew also thrives in warm, dry conditions, so lay a mulch in spring and spray the leaves with liquid seaweed every week or so.

Roses can be badly damaged by greenfly. If the garden is managed sustainably and without the use of synthetic chemicals, however, there should be enough beneficial insects around - hoverflies, parasitoid wasps and ladybirds - to keep these sap suckers under control. You can also spray insecticidal soap over bushes in the evening when there are no flying insects around.

Although most pimpinellifolias only flower once, one hybrid, Stanwell Perpetual, keeps flowering into autumn, just like modern climbers, shrub roses, hybrid teas and floribundas. When pruned during the flowering season, they produce an even better display throughout the summer. Of course, major or renovative pruning is done between late autumn and very early spring, but summer pruning, or deadheading, also pays dividends.

Everyone knows that deadheading stimulates further flowering and tidies away decaying petals which could smother fresh buds and possibly cause disease. The question is: what's the best way of deadheading? Unsurprisingly, experts offer lots of contradictory answers.

One of these methods, for single flowers, is to nip off the fading flowerheads just below the developing hip. It's a fair hassle doing this with clusters. To ensure a continuous display, however, you should remove individual flowers as they wither. A second option is to cut back to the first or second leaf below the bloom. The third technique is to remove the spent bloom along with a stalk containing five leaflets.

Restricting deadheading to nipping off the blooms leaves you with an unsightly mass of dead shoots, very like hedgehog prickles. At the other extreme, removing 15-25cm of stem is pretty drastic. This suggests the best compromise is to cut to the first or second leaflet. Inevitably, it takes longer for the rose to put on enough growth to compensate for severe pruning, but a light prune lets the bush recover and achieve another flush of flowers more quickly.

This is especially important in Scotland. Plants always grow more slowly here because of the weaker sun and lower temperatures. Light pruning ensures a second and third flush after around five weeks, but you will have to wait two or three months after severe deadheading. I should stress that these times vary dramatically according to the kind of summer we have.