If your garden is under siege by sap-sucking aphids, you’re not alone – it was predicted by the RHS due to a warm spring.
Over the past few weeks, you’ve likely noticed clouds of greenfly engulfing the stems and buds of your perennials or roses, or blackfly leaving their signature trails on your clematis.
The RHS had warned back in May that the balmy spring weather was encouraging rapid and early growth of these colonies, with acers, roses and honeysuckle now teeming with aphids. Moreover, some species that were previously confined to glasshouses are believed to be venturing into beds and borders, finding new plant hosts to feast upon.
Dr Stephanie Bird, RHS senior plant health scientist, explains: “This is the time of year when you’d expect to see more aphids. Aphids will overwinter or there will be eggs which will hatch out and then populations build up.”
While 2024 saw an explosion in the slug population due to the warm, wet weather, 2025 has been declared the year of the aphid by the RHS. The number of inquiries it has received about these tiny sap-sucking insects up until May has increased.
Dr Bird adds: “A lot of the aphids we have on our garden plants will have a different summer host that they’ll start moving to, and this is the point in the year when predators haven’t actually started controlling populations.”
The UK is home to an array of more than 500 species of aphids, coming in a kaleidoscope of colours including red, yellow, black, green, brown and pink. These tiny sap-suckers have a penchant for specific plants or display an insatiable appetite for a broad range of hosts.
Their numbers are at the mercy of the British weather, with warm, dry springs and summers providing the perfect conditions for these pests to flourish.
“Aphids’ life cycles are temperature dependent, and the slightly warmer weather means they are able to reproduce and build up their numbers slightly quicker,” Dr Bird has revealed. She also notes that milder winters can kick-start their activity sooner than usual.
Aphids don’t need a partner to reproduce
“They don’t need to find a partner and can reproduce asexually. It’s a bit like Russian dolls. Inside one aphid there is another aphid and inside that aphid there’s another one,” Dr Bird said.
This unique reproductive strategy allows their populations to explode in no time.
How much damage can aphids do?
While many plants can shrug off their feeding frenzies without any serious damage, large colonies can stunt plant growth, cause deformities and leave behind a sticky mess known as honeydew, which becomes a breeding ground for unsightly sooty moulds. Some aphids even spread plant viruses.
“They’re unlikely to kill plants, especially established ones,” Dr Bird reassures gardeners. “For instance, if you’ve a cherry tree which has distorted leaves which are black and sticky, and is covered in cherry black aphids, you will still get cherries off that tree.”
In essence, while aphids may not spell doom for your garden flora, they can certainly detract from its beauty, according to Dr Bird.
Who are their natural foes?
Parasitic organisms like wasp larvae grow within the aphids, ultimately leading to their demise. Other predators include birds, predatory midges, earwigs, ladybirds and their offspring, lacewing larvae and hoverfly larvae.
“Hoverflies are beneficial pollinating insects and their larvae feed on aphids,” Dr Bird explains.
“Having aphids in your garden is part of the natural garden ecosystem. You need these types of insects to feed things higher up in the food chain,” she adds.
Hayley Jones, principal entomologist at the RHS, continues: “Understanding how they can be managed through simple planting choices or encouragement of natural predators will help minimise damage and potential plant losses while maintaining a healthy garden ecosystem.”
How can you discourage them?
The RHS advises gardeners to tolerate them where possible, but if you can’t, use your finger and thumb to squash colonies and check plants frequently before the damage has developed. Don’t use pesticides, it says, because they reduce biodiversity, including natural enemies, and impact soil health.
Encourage natural enemies of aphids into your garden by planting pollinator-friendly plants.
Vulnerable plants
Aphids are attracted to many plants. Some are specific to which plant they will invade, such as rose aphids.
Others will inhabit many different plants.
“They generally inhabit the same sorts of places, so you’ll find them a lot of the time on the undersides of leaves, but they also like the developing softer tissues around flowers and buds,” Dr Bird explains.
Which plants are less susceptible?
Plants such as ornamental grasses and ferns tend not to be troubled by aphids, notes Dr Bird.