Guide to Rose health
Roses are amongst the most beautiful flowering shrubs grown in our gardens, bearing blooms which, though many and varied in shape and scent, can all be agreed to positively ooze class and elegance. Unfortunately, they’re also amongst the plants most likely to be oozing with sticky sap, spattered with powdery splotches of mildew, or cheerfully festooned with browning, soggy blooms, like so many broken Christmas lights.
If you’ve ever had roses in your garden, I’m sure you’ll know the pain of trying to nurture a favourite rose through a dizzying array of different illnesses in the (often vain) hope that it will put on a good show in spite of a wet summer. The first Gardeners’ World Awards, held in 2009, summed up the frustration of growing roses, with the embattled plants topping the “Most Loved” and the “Most Hated” categories of the gardening poll!
Here at Lymefield, we want to help you to get the most out of your roses, both new and old. Rosescanbe very easy to look after, and their versatility and old-fashioned charm, like a tailored suit, make them an indispensable addition to the garden. The real challenge to growing roses is pinning down quite what the problem is, so to help get you started, we’ve compiled a shortlist of some of the most common problems affecting roses in the garden, with a view to explaining what to look for, why it happens, and how you can keep it from happening again.
So without further ado, here’s Lymefield’s Most [Un]Wanted: Rose Pests & Diseases.
I can see little green insects on my rose!
What it looks like
Hungry droves of tiny green (or black) insects cluster under leaves or swamp the vulnerable top-growth of the rose bush. The adult bugs may have wings, depending on species. You might find your buds and foliage covered in a sticky substance that the insects secrete.
Why it happens
These insects are aphids (sometimes known as greenfly or blackfly), an extraordinarily successful group of sap-sucking insects that are capable of rapidly reproducing throughout the year by a process known asparthenogenesis (‘virgin birth’), through which a female aphid can reproduce without the need of a male. This means that a single aphid landing on a new host plant can give birth to literally thousands of new aphids over the course of the growing season. Some aphid species can even give birth to live young that are already pregnant with the next generation!
Unfortunately, with all of those tiny sucking mouthparts to feed, plant health is affected. The main things to watch out for are:
- Reduced growth and vigour
- Tender new shoots that wilt or new buds that bear curled, warped leaves in heavy infestations
- Secondary infections, such as the spread of unsightly black sooty moulds over the sticky honeydew or frass produced by the aphids
How you can keep it from happening again
A spring and summer infestation of aphids ought to be added to Benjamin Franklin’s famous idiom, ‘…nothing can be said to be certain, except death, taxes,and aphids’. To preserve your sanity, it’s easiest to accept that there will always be aphids present somewhere in your garden (even over winter, although usually as eggs), and they will always ultimately converge on your roses when the opportunity presents itself. However, there are still a variety of options available to treat or reduce infestations:
Organic Solutions:
- Try growingnasturtiums orcosmos as sacrificial plants – plants that are so irresistible to pests like aphids that their presence as a food source might reduce the burden on your roses. Nasturtiums and cosmos are available as part of our bedding range in the Garden Centre.
- Aphids aren’t very fast, so they’re very easy tosquash by hand. If you’d rather not be caught green-handed and sticky by a vengeful giant aphid (nb: currently unknown to science), then a variety of gardening gloves are available to buy in the Garden Centre, to help you hide the evidence.
- Soapy water in a spray bottle can put a dent in aphid numbers, as it seems to either suffocate the hapless bugs or disrupt their cell membranes. The liquid solution has to coat the insects themselves, and it doesn’t last long, so there’s slightly less risk of affecting beneficial insects like pollinators or predators. Spray bottles are available in the Garden Centre.
Chemical Solutions:
- A systemic insecticide can be applied to the plant, rather than the aphids specifically. Aphids feeding on your roses will die, and the plants will remain toxic to future generations of aphids (reapplication may be necessary). Probably best reserved for extreme outbreaks, as the solution is also toxic to pollinators.
My rose has black spots on its leaves!
What it looks like
Black lesions appear on the leaves in spring, often fringed with yellow. Leaves are readily shed, and unsightly black, textured scabs can also appear on the stems in more severe infections.
Why it happens
Ah, the creatively-titled Rose black spot. Much like the Black Spot ofTreasure Island, this fungal infection is met with dread by gardeners, but fortunately, the similarities stop there, as the disease is rarely fatal. The spores colonise new parts of the plant by wind and by rain-splash (whereby water hits infected leaves and splashes across uninfected areas of the plant). The loss of leaves in severe infections can greatly reduce the vigour of the plant.
How you can keep it from happening again
Black spot is often credited with the decline in popularity of the English rose garden. It spreads rapidly from rose to rose, and many strains ofDiplocarpon rosae (the fungus responsible) exist, making treatment difficult. However, a good treatment regime might include:
Organic Solutions
- Carefully remove all infected plant matter, including leaves and stems. Where a rose has many stem lesions and plant health is already so poor that it is unlikely to withstand a hard prune, then disposal of the plant may be necessary. Secateurs and hard-wearing leather gloves are available in the Garden Centre for particularly thorny encounters.
- Mulch around the plants with manure every spring, improving plant vigour and smothering fallen leaves to prevent the spread of spores.
- Choose a resistant rose variety! Whilst far from immune, disease-resistant cultivars such as‘Sexy Rexy’, and ‘Loving Memory’ promise less of an uphill battle against fungal infection.
- Avoid monoculture (where only one kind of plant is grown, as in a rose garden), and incorporate your rose into a mixed planting with a variety of herbaceous perennials such as Salvias, Geraniums and Foxgloves. A beautiful and savvy solution!
Chemical Solutions
- A systemic fungicide will protect plants for up to 3 weeks, and will also control for other fungal infections. Water or spray on to the plant according to the recommended dosage.
There are tiny orange spots on my rose plant’s leaves!
What it looks like
Plants show yellow lesions or splotches on the surface of leaves. On the underside of the leaf, below the yellow lesions, are the telltale mounds of powdery orange spores. The infection can also warp young stems and gird them with the same orange dust.
Why it happens
Older rose varieties are more commonly infected by Rose rust fungus than newer, more resistant varieties. Outbreaks are most likely to occur in cool, wet spells. Whilst rose rust is less common than black spot, its resting spores can overwinter on objects other than the plant itself, such as fences and the soil surface. These spores are spread by wind and rain splash.
How you can keep it from happening again
Rose rust infections are unlikely to cause serious injury to a plant, but they are unsightly and in some extreme cases, a rose may have to be replaced. Treatment is largely the same as for black spot, so refer to the advice above. We’ve generally found that cultivars that are resistant to black spot hardly seem to develop rose rust at all, but we might just be lucky!
I don’t actually have any roses!
What it looks like
A gaping hole where a rose ought to be.
Why it happens
Cowardice.
How you can keep it from happening again
