"These roses are heady with scent," smiles Cissy Bullock, florist and co-founder of the Bedfordshire-based School of Sustainable Floristry, as she buries her nose into an arrangement of voluminous, blush-pink flowers. Their fragrance tells us a lot about how they've been grown, she explains: "Most commercial growers breed out the scent so they last longer." They look different too; these aren't the ramrod-straight stems usually available in florists and supermarkets. The stems are shorter, some have multiple heads and, she says, "they look like they've come from the garden."

But best, she adds, is that "because these flowers are grown regeneratively, without artificial pesticides or fertilisers, the soil is not in a cycle of continuous depletion, as it would be with conventional farming."

When you know what you're looking for, it's easy to identify a bouquet that's been grown in the British elements, without artificial chemicals. "Sustainable British floristry is about being ingredient-led and letting the ingredients breathe," says Bullock. "It's as much about working with the [space around them] as with the flowers. This creates more movement and depth, and feels more naturalistic."

The sustainable British flower movement is blossoming. "The number of small-scale UK growers has grown exponentially," says Georgie Newbery, a Somerset florist, flower farmer and an external chair of Flowers From the Farm (FFTF), a trade body for sustainable British flower growers. "Fifteen years ago, I could count on one hand the number of growers like me. Now we have more than 1,000 members." Newbery says her 7-acre flower farm, more than half of which is allocated to orchards, woodland and wilded spaces, isn't treated with "anything more complicated than organic compost".

Last weekend, Strawberry Hill House Flower Festival returned to London with displays from more than 30 floral designers using homegrown British flowers. "The elements play a big part in how the flowers grow," notes the festival's founder Leigh Chappell. "They might get blown to the ground by the wind, then grow back up again; sometimes things splay or jag at different angles. It makes things interesting."

It's a marked contrast to most imported flowers, Chappell says, "which are all grown to look the same". According to the British Florist Association, 85-90 per cent of the UK's cut flowers are imported -- many via the Netherlands, the global trade centre for flowers. Of those imports, government department Defra's latest figures state that 65 per cent are grown within the EU and 35 per cent outside it -- notably in Kenya, Ethiopia and Colombia.

Which brings us to the thorny issue of pesticide use in mass-grown flowers. "Because flowers are a natural product, people assume they're grown naturally," says Bullock, who has just published a report for florists on her website. The aim is to better inform them on the cut-flower supply chain, on the questions they should be asking, and what sustainable choices are available to them.

"The use of pesticides is intensive in floriculture," says Margriet Mantingh, president of the Dutch arm of the anti-pesticide charity Pesticide Action Network (PAN). "Flowers are very sensitive to disease and insects, and retailers say the public wants perfect flowers. Most worrying is that many pesticides banned in Europe are still produced here, then exported and used in Africa or South America, where there are fewer restrictions." PAN International has a list of the 568 most used pesticides globally for agriculture -- about 500 are banned in the EU; in Kenya, only 28 are banned, in Ethiopia, 12, and in Colombia, 41. There are no EU or UK laws limiting any kind of pesticide residue on non-edible flowers.

This February, PAN tested 13 bouquets from Dutch florists, supermarkets and online retailers, and identified 71 different pesticides -- 39 per cent of which are banned in the EU, and 69 per cent which are classified as posing health risks to humans and biodiversity, according to the EU Pesticides Database and PAN's list of highly hazardous pesticides. "Although consumers are not really at risk, because they're not handling the flowers daily," says Mantingh, "florists and growers are very exposed."

Last year the death of a former French florist's 11-year-old daughter, Emmy Marivain, was a wake-up call for the industry. Her seven-year battle with leukaemia was found by the French Pesticide Victims Compensation Fund (a national body established to compensate those suffering with illnesses caused by pesticides) to be causally linked to her mother's exposure to floriculture pesticides when Emmy was in the womb.

A 2018 Belgian study of 25 florists and 90 bouquets found 107 pesticides on the bouquets, 111 on the florists' gloves and 70 in their urine. Of particular concern was florists' exposure to the pesticide clofentezine, which the US Environmental Protection Agency has classified as a possible human carcinogen; the florists were exposed to sometimes four times above acceptable limits. There are also fears about certain EU-compliant pesticides -- last year, a Dutch court banned a lily grower from using all but four pesticides, citing "substantial evidence" of a link between pesticides and conditions such as Parkinson's and Alzheimer's.

Flowers are sensitive to disease and insects, and retailers say the public wants perfect flowers. Most worrying is that many pesticides banned in Europe are still produced here, then exported

"If consumers were more aware of this, their concerns would rise," says David Bek, a professor of sustainability and economic development at Coventry University who, in 2016, founded the Sustainable Flowers Research Project with University of Surrey sociologist Jill Timms to examine the cut-flowers supply chain. "The flower industry is way behind the food industry in ethical standards," he adds. "After various exposés, it's been playing catch-up."

So how can consumers buy with confidence? Buying British isn't enough, says Bek. "Geographical terms are not [guarantees] of sustainability. Bigger [UK] growers -- and even some smaller ones -- will be using chemicals." Organic Blooms in Bristol, Sitopia in London, Ward Farm Flowers in Exeter, Over the Hedge in Sheffield, and Daylesford Organic in the Cotswolds are among the few UK flower growers that are certified organic by the Soil Association; other sustainable certifications include the Leaf Marque, Biodynamic Certification and the Dutch MPS Florimark.

However, small-scale growers are often excluded from sustainable accreditations, says Olivia Wilson, grower, florist and co-founder of SSAW Collective, an ecological campaigning group; she co-authored Bullock's report for florists. "Most certifications are prohibitively expensive, and the metrics aren't always relevant to [small producers]," she says. What's more, she adds, "a lot of certifications aren't [visible] to consumers, or even florists".

Waitrose claims that 44 per cent of its bouquets are UK-sourced and Leaf-accredited, and are labelled as such. Leaf's certification policies state that any pesticide used must be approved in the country in which the flower producer is located.

The best rule of thumb is to buy local and seasonal, just as with food. Even better is to buy directly from the growers; organic purveyors such as Organic Blooms and Clover Nursery (both via organic food delivery company Abel & Cole), Burnt Fen Flowers (not certified organic but organic in principle) and the aforementioned Daylesford Organic offer flowers across the UK by mail order.

"If something is growing naturally, at that time of year, local to you, then it won't need to be forced or heated externally," says Timms. "That's not to say that no pesticides have been used, but if it's a local farm, you can visit it; you're more likely to build up a relationship with them." Plus, skipping out the intermediary to buy direct from growers enables a longer vase life. FFTF is working on a set of sustainability standards for the British floriculture industry, and has a directory of local growers, which is a useful starting point but doesn't yet exclude those who use pesticides (some listings make explicit that they are chemical-free, for others, it's up to us to ask the question).

Back in Bullock's studio, she turns to some pink and lilac sweet peas: "Well, their vase life isn't 14 days," she shrugs, "but that's kind of the point. When a sweet pea goes over, it's still glorious, because then you get the peas." She points to some healthy-looking peapods dangling from the stems. "That's the bit that's interesting."

How sustainable is your bunch of flowers?