We are not picking on red roses here, white, yellow, purple and pink are all the same. But the fact is a flower grown in a heated greenhouse, then flown to another country ready for you to buy in the middle of the winter to just look nice on your windowsill – there is a big environmental cost to that.
A beautiful rose grown in your own garden, picked in the summer when it is flowering naturally has a positive environmental impact: the plant is using carbon from the atmosphere to grow, and bees and insects benefit from its nectar to make honey, feed their colonies and support the circle of life. We love naturally grown roses!
But, grown in a heated greenhouse, or flown long distances and transported in refrigerated containers is not good. Out of season cut flowers are rekoned to be one of the most carbon unfriendly purchases you can make at the shops. Some countries such as the Netherlands allow flower growers to use subsidised electricity to heat their glasshouses in winter (remember the Netherlands is pretty cold in winter), which means they are economical to produce, but contribute up to a whopping 2kg of C02 emissions each.
And that does not include the fact that the land could otherwise be used to grow food, or at least allow a little biodiversity. In intensive flower farms, high quantities of fertilisers needed to force the plants into unnatural flowering cause run off polluting natural watercourses and affecting the natural flora and fauna. Intensively grown flowers are sprayed with chemicals to keep pests away because who wants to buy a flower with a huge chunk of the petal eaten by a caterpillar? And preservatives are sometimes sprayed to keep them looking better for just a day or two more to give them a longer shelf life. Poorer countries which are often big flower producers (for example Colombia, Ecuador and Kenya) have less stringent safety regimes for their workers, and there are cases of workers suffering the effects of chemical toxicity. This article from TED highlights some of these issues https://ideas.ted.com/the-environmental-impact-of-cut-flowers-not-so-rosy/
So, what are your choices? Flowers in season, grown in your own country are the best choice. When buying flowers, ask how far they have travelled. If available, look for a Fairtrade or similar certification, because that should guarantee better environmental and employment standards.
Alternatively, a potted plant will give pleasure for many months or even years. And you can have the satisfaction of nurturing it yourself and seeing it grow.