Trendy Double-Flowered Blooms and Ornamental Grasses Are Starving Out Garden Pollinators

Fashionable trends in urban and private garden landscaping — double-flowered varieties and ornamental grasses grown without their traditional herbal companions — are turning attractive-looking flowerbeds into veritable ecological deserts for pollinating insects. This is the conclusion of a recent piece examining landscape architecture and its impact on bees, butterflies and other pollinators.

Double flowers — those with an excessive number of petals — have been cultivated by humans since antiquity. The ancient Greek philosopher Theophrastus wrote about them in the 3rd century BC, describing wild roses with unusually abundant petals. In ancient Rome, fragrant double roses were grown on an industrial scale for their essential oils, while in China during the Tang dynasty (around 750 AD) the imperial gardens of Chang'an were transformed into vast peony parks through deliberate selection of double-flowered forms.

Why Double Flowers Are Bad News for Bees

As long as such flowers remained rare — confined to palace gardens, or later appearing sparingly in grandmother's beds alongside mint, lemon balm, sage and other nectar-rich herbs — they posed no real threat to insects. But the excess of petals in many modern garden cultivars often blocks access to nectar and pollen, or prevents the plant from producing them at all, rendering such flowers essentially useless to pollinators.

A similar effect comes from another popular trend: gardens filled with ornamental grasses, often non-native and sometimes invasive, paired with only a meagre selection of perennials. Take the increasingly popular runaway weed argentine vervain (Verbena bonariensis), which — thanks to climate change — is spreading more aggressively across Czechia. It feeds only generalist insects that aren't picky about their food sources, while doing nothing for the rare specialist species that are suffering the most from population collapse across Europe.

A Trap Rather Than a Help — and Sometimes a Death Sentence

Scientists describe a phenomenon known as "pollinator hijacking": a plant offering abundant nectar, such as the invasive butterfly bush (Buddleja davidii), draws in virtually all generalist insects, leaving native plant species without pollinators. Even more dangerous is so-called phenological mismatch: when a non-native plant blooms briefly but intensely en masse, bees mistake this for a lasting abundance and build more nests than usual — but once the flowering abruptly ends, the larvae are left without alternative food sources, and part of the population dies off.

The most extreme case is when a plant directly kills pollinators. Back in 2017, researchers published a study on the North American showy evening primrose (Oenothera speciosa): its flowers attract the European hummingbird hawk-moth (Macroglossum stellatarum), but stiff internal hairs inside the bloom act like a mechanical lock on the moth's long proboscis. The insect becomes trapped and, in most cases, dies inside the flower. Despite this, the plant is still sold in garden nurseries today.

How Other Countries Are Tackling the Problem

Several European cities and countries have already rethought their approach to green landscaping. In Ireland, the national pollinator protection plan officially recommends that gardeners and municipalities choose simple, single-flowered varieties of blooms and ornamental cherries. In Berlin, using regionally native plants has been a legal requirement for open natural areas since 2020, though for city parks it remains only a recommendation. In Vienna, the municipal parks department selects perennials with staggered blooming periods so insects have access to food year-round. In Paris, the "Permis de végétaliser" programme lets residents green up public spaces using a recommended plant list that flags each species' local origin. In the canton of Zurich, the official beekeeping authority advises using wild native species instead of exotic ornamental cultivars.

The article's authors note that plenty of single-flowered rose varieties remain available on the market — they tend to be hardier in winter, less prone to disease, and in autumn they reward the eye with red rosehips, which double-flowered varieties never produce. Solving the problem, the piece stresses, doesn't require abandoning ornamental plants altogether: it's enough to favour simple-flowering, regionally native species in public green spaces, while reserving lush double-flowered varieties for collectors' gardens and purely decorative beds.

Read also: Prague Castle from Within: 9 Places Within the Fortress You Shouldn't Miss

Source: ekolist.cz