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Let's talk about roses

Becky Martin, the nursery gardener provides five easy steps to look after roses.

It is often said that you can’t grow roses in Cornwall but this is simply not the case. You only have to drive through Cornish towns and villages to see flourishing roses. They are tough plants. It is hard to kill them by mistake, but to have a rose festooned with blooms, healthy foliage and a heady perfume requires a little effort. There is abundant literature on rose-growing, as well as plentiful folklore, but here are five basic steps for growing healthy roses.

Choose a suitable variety.

Breeders are continuously developing new roses to meet changes in taste and demand. Many of us have a sentimental attachment to a particular rose we remember from times past, but new varieties have been bred for disease resistance, fragrance and repeat flowering. They may be unfamiliar and have less romantic names but are often better performers. Rose diseases mutate and develop new strains, just as human diseases do, and older varieties may not be as resistant to the newer strains.

To avoid disappointment do not choose your rose on the basis of a seductive photograph. Roses with wonderful double cabbage-like blooms are not the best choice in Cornwall. With high rainfall they can become waterlogged and droop, the outer petals go brown and lock, preventing the flower from opening properly. This is called balling.

Consider your soil and site, the amount of sun, available space, container or open ground, access for pruning, closeness to a path, and so on. Good rose suppliers will have lists of plants suitable for specific growing situations.

Plant your rose carefully.

To give it the best start, spend a bit of time doing this properly. Make your hole big enough to accommodate the roots comfortably without bending them. Break up the soil at the bottom of the hole. Enrich the soil by adding some organic matter to provide moisture retention and nutrients. This is particularly important on poor soils. Garden compost, or blood fish and bone, mixed with the soil is ideal. The use of mycorrhizal fungi is recommended to help the rose get off to a good start. It can be sprinkled on the rootball of a potted rose before lowering into the hole. For a bare root rose, the easiest way is to wet the roots, then sprinkle over the fungus granules which will then stick to the roots. It is best not to plant your rose in a site previously occupied by another rose. It may suffer from a condition called replant disorder, which will stop the new rose from establishing itself and growing well.

The rose needs to be planted at the correct level. At the bottom of the stems you will see a bulge of woody material between the roots and the stems. This is the join where the cultivar has been grafted onto the rootstock. This should be one inch, or 2.5cm, below the soil surface. Once you have placed your rose in its hole, backfill with the enriched soil making sure to get it in between the roots of your bare root rose. Firm it in and water generously. At this point you may see the soil surface drop as it settles around the roots. In this case add a little more soil to bring it up to the correct level.

Feed and water your rose.

Roses are greedy feeders. They will not flower generously unless fed generously. They will quickly use up all the nutrients in the soil and require additional fertiliser, this is especially true of roses in containers which will require frequent feeding throughout the season. A good regime is to mulch with compost or well-rotted manure in the spring, and thereafter feed with a proprietary rose food several times over the summer. Do not feed late in the summer as this will encourage soft sappy growth which is more susceptible to disease as the weather cools and autumn draws in. Water should always be applied to the soil around the base of the rose, and not on the foliage. It is better to drench your plant once a week than give it a dribble every day. Do not wait until the plant is showing signs of suffering. Examine the soil around the plant to check it is moist below the top few inches.

Look out for pests and diseases

Accept the fact that you probably will get some, but with good management the problem can be kept to a minor nuisance level, and not allowed to threaten the health or wellbeing of the rose. The commonest and most annoying problems are blackspot, powdery mildew, and aphids.

Powdery mildew appears as a white dusting on the leaves and sometimes also the stems and flowers of the rose. It is caused by a fungus and occurs where there is poor air movement, dry soil and humid air. Blackspot is possibly the most difficult and intractable of the rose diseases, also caused by a fungus. The spores lurk in the soil beneath the infected plant and survive the winter to reinfect new growth the following spring. Black lesions appear on the leaves, which turn yellow and fall off, making an ugly and unhealthy plant with no vigour. For both these fungal diseases a degree of prevention is afforded by good cultivation techniques, namely enhancing airflow through the plants, and removal of all infected material (which should be burned and not composted), and watering the soil and not the foliage. A thick mulch applied in the spring before growth starts can smother the spores on the soil just below the plant. Additional protection can be achieved by maximising the rose’s natural health and disease resistance using solutions such as SB Plant Invigorator. If the disease becomes too advanced, either put up with it, remove the rose, or treat using a proprietary fungicide which will need to be applied with a sprayer at regular intervals through the growing season.

Aphids appear on the buds and shoots of the rose. Heavy infestations can cause distorted or stunted growth and weaken the plant. However, aphids are a vital food source for garden birds, and a well-balanced garden will have a few aphids and plenty of well-fed birds. If possible leave them, or remove using a soap solution which has no detrimental effect on wildlife.

If you do resort to chemical treatment use freshly purchased products in accordance with the labels. There are products for roses which combine a fungicide with an insecticide, but do you really need to use an insecticide? Be wary of the old bottle of “spray” lurking in the garage or garden shed for years. It may well have deteriorated and no longer be effective, but also may contain banned and harmful chemicals. There is a useful and easy to understand article here which explains

Prune and deadhead your roses

Don’t fret unduly over this. The purpose of pruning is to keep the plant within bounds and encourage plentiful blooms. Roses flourished centuries before secateurs were invented.

The first principles of pruning are to remove any dead, diseased or damaged shoots. This can be done at any time of year, though it is easier to see what you are doing in winter when the plant is dormant and has no leaves. For shrub roses, it is a good idea to cut the rose back by about a third or half in the autumn simply to reduce rocking in the wind which could loosen the roots and damage the plant. The main pruning is then carried out in early spring. The aim is to produce a bush with strong healthy stems spreading out in the desired shape. Any weak, spindly or crossing stems should be removed from the base. Traditionally we are taught to make a cut above an outward facing bud. Conveniently, the buds for next year’s growth are visible along the stems so you can see the direction in which they will grow. Be brave, prune down to a low level and you will have a well-shaped bush. If you don’t prune hard you will end up with a taller lanky bush. Climbing and rambling roses require different pruning, and tying in at the same time. There is an easy and helpful guide here.

Deadheading is simply the removal of spent flowers which turn brown and are unsightly. Cut off the dead flower with its stalk down to the next leaf shoot, or the shoot below that. In the case of cluster-flowered roses, remove individual blooms as they fade, then take out the whole cluster once it has finished. Make the cut above a strong bud on the stem.

Always use sharp secateurs to make clean cuts and minimise the risk of disease entering the stem.