Is there any evidence that the flower-selling industry is responsible for creating Mother's day, or at least for pushing it to the popularity it has now?
Yes.
In the USA, the current Mother's Day holiday was enacted by a joint resolution of Congress on May 8th, 1914.
Prior to being made a federally recognized day, florists did play a role in promoting the idea.
In the August 1910 Proceedings of the 26th Convention of the Society of American Florists it is recorded Anna Jarvis's attempt to create Mother's Day "has proven so beneficial to the business" and a unanimous resolution was passed to publicly recognize her efforts.
In the 15 May 1913 The Florist Review, volume 32, page 17, there is an article LESSONS OF MOTHERS' DAY:
Chief of the lessons of Mothers' day is that of the power of publicity; second, the effectiveness of concerted effort.
The florists made Mothers' day. But for the florists the lady to whom we are indebted for the beautiful idea would never have got anywhere with it.
Mothers' day has made progress just in proportion to the push the florists put behind it—where the florists sat supine, there Mothers' day is practically unknown
Also in the 1913 American Florist, Volume 40, page 823 there is an article "Mothers' Day":
...So this is the warning florists should heed: Mothers' day is yet a young institution. Indeed it is of such recent birth it can hardly be called an institution yet. The next two or three years will probably decide whether it is to live or to die out as suddenly as it sprang into being. And its future rests with the florists themselves... And in a few years the day will be remembered as a fad that did not last. But if they make the flowers as cheap as possible they will be repaid time and time again for years to come. To make Mothers' day popular it is necessary to induce as many people as possible to wear flowers. To do this it is necessary to make the flowers cheap. Whether Miss Jarvis' beautiful idea is to die abornin' or is to live in proclamations and people's hearts depends solely upon the florists themselves.
Only the following year was Mother's Day federally recognized.
Florists did not invent Mother's Day, Anna Jarvis did. However, Anna Jarvis initially linked Mother's Day to carnations. A previous attempt by Julia Ward Howe to create a national Mother's Day, had no relationship to flowers, and was celebrated for a few years around 1873, but quickly died out. Florists made efforts to prevent the current Mother's Day from dying as a fad, prior to being federally recognized, because it was great for business.
