Are Day Lilies invasive?

Last summer I was given some Day Lilies by my father's wife from their garden. They grow all over the place and seem to be spreading quite madly. I didn't have a suitable spot for them when I got home so I planted them in a big pot. They are now doing very well and have laves that are almost 2 dm. If I plant them in my borders, will the take over or will that take years before they spread too far.

In my experience they do spread, but the clumps just get bigger rather than them popping up all over the place. I thik it also depends on what variety they are...there was a clump of a rather ho hum orange hemerocallis when I moved here, I got fed up with it and dug it up as it didn't produce enough flowers to earn its keep. I must have missed some bits, as there are a couple of little plants there now, but I'll see what they do. I've planted out another couple,Kathereine Woodbury (I think) which has pinkish scented flowers, and a pale cream one. They've been in a year or so and haven't got massive by any means.

I have had mine for years and it has not popped up anywhere else, unless I put divisions there. I do dead head on a daily basis .

Mine haven't gone mad in the garden. I have split one up growing in a container and they look like they are doing ok at the moment. 

If they'r ehappy the clumps get bigger each year but that just means you can lift and divide them and have more plants for your garden or to swap with firends and rellies. I have several forms in my garden and they're very forgiving, happy to grow in sun or part shade and in well drained or moist soils.  Just make sure you scatter wildlife friendly slug pellets as the new shoots emerge in sprng cos the slugs love them.

Hmmm. I find them invasive because they are very happy in my garden and spread out into the lawn and swamp other plants.

I find lifting and dividing them difficult (but I am feeble) and doing so just invigorates the clumps and they spread even further. As I don't want any more clumps I have put divisions on the compost heap where they are now thriving! So I will have to dig them up from there.

They are the first green shoots which appear in late winter, cope with any amount of snow and frost and have been untouched by slugs here -perhaps because they wake up well before the slugs do.

I can't find anyone locally who wants any as they all have the same problem.

In conclusion -you have to love them to grow them and they do have some things going for them.

Much will depend upon which day lily you have.  The early ones, mostly yellow or sandy-brown coloured, can become a bit much in some areas. The later hybrids - in every colour of the rainbow - don't do more than become a larger clump if happy.  

Mine have never spread, the same ones show their heads every year

Mine are the yellow and sandy-brown types! Good description of the colour there, Bookertoo.