For me it's Foxgloves, Corydalis lutea, Columbine, Persicaria superbum, Ladies Mantle, Several Campanulas, Astrantia, Perennial Geraniums, Cyclemen (ants), Ferns, Kenilworth Ivy, Euphorbias, some Ornamental Grasses, I'm sure there's more but can't think of them at the moment.

Annette

Digitalis, great blue lobelia, aquilegia, fernleaf bleeding heart, snowdrops, echinacea ... and this year I found a volunteer white petunia.

What a charming post - and I so agree. I think there is a sense of place and history as plants find themselves here and there and I love the continuity of it. Mine come and go and I think especially thru the compost pile.

Lamb's ear, rose campion, gloriosa daisies, siberian iris, nicotiana, larkspur, cleome, perennial hibiscus, nigella 'love in a mist', phlox, sunflowers that come up from the bird feeders.

Arrrg! Tried to log in yesterday to comment and couldn't get on...

-Annette, CYCLAMEN reseeding?! That doesn't sound like a bad thing at all to me! How long does it usually take for the seeds to mature enough to bloom? Like three years or so?

-Cindy, the birds 'plant' a lot of things for me too! Last year when I had the sunflower seed mix birdfood I had some HUGE plants pop up. When I planted some myself this year naturally they are little weakling plants, LOL! Guess those birds to a better job of it than me... ;-)
CMK

C, I've even had a few cyclamen blooming in their second year, that is seed I've sown myself. I think it's ants that pack seed around in the garden. I have them in a couple of spots where I definitely didn't plant them. Lithodora is another that has plunked itself down right in the middle of a patch of violets.

Annette

My cushion spruge has appeared on the berm under the canna I planted. New berm dirt, so I think they migrated with the canna bulbs which I dug up last year from near the spruge grouping. I didn't expect that one. I read somewhere that plants are the healthiest when they settle where they want to grow, so I try and leave them if possible. My Rudbeckia Hirta popped up in a couple of places this year that were just perfect.

I have Filipendula rubra that was a beautiful large clump in an area of my cottage garden. Over the years it has roamed outside the fenced area and it comes up with only a couple shoots in each spot. But the flowers are enough to be pretty enough to show off just a bit. Nothing left of it in the original spot.

My Herbstonne rudbeckia roams all over the place. Quite the thug actually. I only let that come up in certain spots depending on how close it is to other perennials. The others get dug up and usually given away to friends with a disclaimer. A little OT but I actually started to cut this rudbeckia down by half and it now blooms at about 5' instead of 8'.

I've had a lot of reseeding of Heuchera 'Palace Purple' and Euphorbia polychroma. I've never had them reseed much but in the past couple years they've gone crazy. I'll generally leave those wherever they wind up. And of course the rose campion is a great reseeder. I shake those seeds everywhere!!

Hey Christin, Don't feel bad about your scraggly weak plants. Any time I've tried to plant sunflowers the chipmunks dig up all the seeds so none ever come up!!

-Annette, thanks for the info. Now I really need to get some hardy Cyclamen, if it is that easy to propagate more of it...

-Susan, my 'Palace Purple' does the same (think I may have mentioned this to you recently ;-) Even have some popping up in the cracks of the patio, which I like. That is interesting, I havenn't had any seedlings from E. polychroma. I didn't have to cut mine down after blooming (no mildew on it this year!) so perhaps a few will show up next year. There are a TON of Euphorbia dulcis 'Chameleon' seedlings. Not a huge fan of this plant, but at least it survives in tough conditions where little else will grow!

'Jack Frost' Brunnera is another that reseeds a lot in my garden. Not sure if I like this or not, since they don't pull up well. At least my seedlings come ((mostly)) true.
CMK

viola. They pop up everywhere and are planted by mother nature throughout my gardens.

The birds also like to distribute mulberry seeds. Yuck.