A varied flowerbed can bring colour and texture into your garden, but some plants are better companions than others. They may look beautiful side by side, but certain varieties can quietly compete for sunlight, water and nutrients beneath the surface.
To help you avoid common planting mistakes, Didrik Dimmen, gardening expert and co-founder of indoor smart garden company Auk, shares the flower pairings to avoid, why they can cause problems, and one tried-and-tested combination that works every time.
Sunflowers and delicate flowers
Sunflowers make a striking addition to mixed borders, but they're not always the easiest neighbours. As heavy feeders with far-reaching roots, they compete for water and nutrients below the soil, often leaving most delicate flowers struggling to establish. Their towering height can also block sunlight, making it even harder for nearby plants to thrive.
'Whenever I'm planting… I always give them their own dedicated space in the garden rather than tucking them in among more delicate flowers,' says Didrik.
Delphiniums or hollyhocks and lavender
While a varied flowerbed looks lovely, Didrik explains how a range of heights can create issues: 'I regularly see tall, fast-growing flowers such as delphiniums or hollyhocks planted directly in front of something lower and sun-loving.'
Lavender is the classic victim of this mistake. 'The taller plant casts shade exactly where the lavender needs full sun. Once that happens, the lavender behind it rarely recovers properly for the rest of the season.'
Mint and other flowers
Mint may look pretty as a flowerbed border, but it's best grown separately. Its vigorous underground root system spreads quickly, taking over nearby plants' space and competing for the water and nutrients they need to grow well. Left unchecked, it can easily damage more delicate flowers.
'I would never let mint share a container with anything else; it needs its own pot or a properly contained space to stop it spreading,' says Didrik.
Why these pairings don't work
The effects of poor flower combinations aren't always obvious straight away. Over time, flowers competing for light, water or nutrients may produce fewer blooms, appear less vigorous or wilt more quickly, even if they're being watered regularly. This is often because they haven't had the space or resources to develop a healthy root system.
Plants that are already under stress are also more susceptible to pests and diseases. Once one plant begins to struggle, problems can spread along the border, making it harder for neighbouring plants to stay healthy.
'By the time a gardener notices something's wrong, it's usually months after the real damage has already been done at the roots,' says Didrik.
A pairing that always works: catmint and roses
'Catmint and roses is a pairing that thrives beautifully together, and I'd recommend it to almost anyone,' says Dirdrik. 'They both need the same sun and soil conditions, so there's no underlying tension between them to begin with, which is more than can be said for a lot of popular pairings'.
Catmint also makes an excellent companion for roses because its shallow roots don't compete for the same nutrients. Better still, it's thought to help deter pests, offering a natural way to protect rose blooms. It's a tried-and-tested pairing that's remained a favourite with gardeners for generations, thanks to the way the two plants thrive alongside one another.
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