These pairings can quietly ruin your garden
Some popular perennials make terrible neighbours. From plants clashing with watering needs to aggressive spreaders, some pairings can quietly ruin your garden — and leave you with a sad-looking flowerbed.
Companion planting is key to a successful garden, but we don't often give much thought to the varieties that won't get along. Plants with different needs compete for the same resources (water, light, food) and will smother or sabotage each other for their own gain, leaving one or both plants to suffer. Peonies and delphiniums, for example, grow at different heights and can block the sun from one another.
If you want healthier plants and better blooms, these common pairings are the ones to avoid. Take a look at which ones the experts suggest:
Planning a garden border? Lavender and hostas might look lovely in the same patch, but according to Julian Palphramand, head of plants at British Garden Centres, they're not a match.
'Lavender wants full sun and freely draining, relatively dry soil, while hostas prefer shade or part shade and consistently moist ground,' he tells us.
'Plant them side by side, and one will unfortunately suffer. Keep lavender with other dry‑garden perennials in the sun and hostas in the damper, shadier borders.'
As well as lavender, fussy hostas don't thrive next to phlox flowers.
'Both like moisture, but the extra shade needed to keep the hosta's foliage pristine creates conditions that push mildew problems in phlox. What looks like a harmonious cottage‑garden combo can quickly turn into a fungal nightmare, so avoid planting these together,' continues Julian.
'Peonies like full sun and resent overcrowding, while tall delphiniums will shade them and steal water and nutrients, leading to fewer, smaller peony blooms,' says Julian.
Instead, he suggests grouping delphiniums behind sun‑tolerant plants that don't mind the competition — such as salvia or daylilies.
Shallow-rooted heuchera, also known as coral bells, are colourful additions to garden borders. But if there's a plant to keep them away from, it's Japanese anemones.
According to Julian, they can get smothered by anemones' dense, spreading mats that steal space, moisture, and nutrients. 'This can fade the coral bells' vibrant foliage,' he says.
Cottage garden essentials, delphiniums and lupins are another duo that don't work together. They are both prone to powdery mildew and aphids, which means if they're too close together, the disease and pests will spread, weakening the tall spikes quickly.
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