Source? If you cut the stems the plants regrow shorter, but next year if you wait a while the stems grow just as long.

My source is simple observation. I did all the mowing as a kid, acres every week. In the spring, chopping down all the new dandelions was satisfying and the grass looked great. By the middle of the summer, dandelions were back but now they were strangely 'smashed' ones that grew no taller than 4", with flattened stems that turned or curled or flowers on short, short stems that bent over.

I'm sure that gene was always there; but billions of mowings over a century of lawn care means its present everywhere. Simple selection?

Ahh, no this is similar to the process that causes Bonsai to work. Dandelions have a fairly massive root with plenty of reserves to regrow after something eat's the top. Mowing simply causes similar responses as a goat would.

Plants can't move around so they evolved to deal with a really wide range of environments and stuff eating them etc.

Nah. Dandelions don't regrow stems; this can't be something done in response to being mowed. The plant doesn't think "I got mowed! I guess I'll grow a different way now".

Its a different growth pattern in the plant. Gotta be driven by genetics.

Dandelions are actually perennials so they will regrow stems several times, and survive multiple years. They will also tend to flower most abundantly in spring, but can re-flower in the fall.

Further, it's not just the stem involved, if your mowing regularly your taking out the leaves.

PS: There are also a few different plants that all look similar. https://en.wikipedia.org/wiki/False_dandelion

Yup the flat ones were none of those. They were really weird knarly mutated plants with exactly the same structure, leaves, stem and flowers as dandelion but grown flat and warped to hug the ground.

I've always wondered about dandelion evolution and mowing. Do you know of any studies done on this?

No! And it needs to be done! I've lived in only a couple of places, and the genetic variety of dandelion (dent-de-lion?) is marvelous. When I grew up they were small modestly sized plants. Then the mowing thing, and a 2nd form of flat plants. Moved to California, they were 4' tall with greyish-green dusty leaves. Moved to an acreage in Iowa, all over the fallow field one year they were bushes about 18" high with 100 blooms - you could have sold them in a garden shop for landscaping!

Mendel should have used dandelions for his gene studies, there is lots more to see!

Meh, there are plenty more cracks in sidewalks, open fields, and poorly kept yards than there are mowed lawns. Dandelion evolution probably isn't optimizing for mowed lawns any time soon.

It's apparently not a crazy idea.

https://news.uoguelph.ca/2014/04/high-school-students-study-...