In the millenniums since silk production began, the industry has found a few ways to reduce its environmental impact. A handful of producers have figured out how to gather silk without killing the pupa. You can also buy wild silk, which uses far less energy and fewer chemicals. Since these niche products aren't widely available, however, it's unlikely that either of these techniques were used to create the silk flowers at your local arts-and-crafts store.
China produces more than 70 percent of the world's silk, while second-place India produces11 percent, so your silk flowers probably took a pretty long journey. But because silk flowers have an indefinite shelf life, they usually travel by sea freight, which requires considerably less energy than air freight. Shipping a one-pound bouquet of artificial roses generates roughly 0.28 pounds of carbon dioxide, or about one-twentieth the emissions that traveling by air creates.
Without more scientific research on the topic, it's impossible to say how many real roses it takes to equal the environmental impact of a bouquet of silk flowers. Keeping a vaseful of silk flowers is likely the environmentally responsible choice in the long run. Just how long? Who knows. But are you seriously considering hauling the same dusty vase of fake flowers out of the closet every year? That might lead to divorce—a much worse environmental consequence than an annual order of roses. The Lantern welcomes your recommendations for eco-responsible flower substitutes in the comments below.