I was wondering if anyone has had experience with these annuals self-sowing, and if so, what varieties?
Bells of Ireland
I have had cosmos self-seed (one of the tall pink and white mixes) and Portulaca (AKA moss rose), whatever the common double mix that my local greenhouse carries. Sorry not to be more helpful with varieties.
Most of the others I haven't grown, so I don't know about, but snapdragon Black Prince and calendula never self-seeded for me.
A few other annuals I have had self-seed:
- Johnny jump-ups, a type of viola
- Nicotiana (AKA flowering tobacco) I like for its lovely evening scent (sort of vanilla-y) and its long bloom from mid-July until a good frost, so that it is the most prolific bloomer in my garden during the late fall. I planted it once about 10 years ago . . .
- Verbena bonariensis has light airy purple flowers beginning in August here.
- Petunias (occasionally)
All of these pull easily if they volunteer where not wanted and will return for many years in this zone.
Cleome, on the other hand, was a bit of a pest and took several years to eliminate after I had let it go to seed one year.
Moss roses, cosmos, and snapdragons self seed for me. The snapdragons come up late and bloom late but are vigorous and full of blooms. After a couple of years moss roses have made a thick mass in the dry soil under my mailbox. The first couple of years I moved seedlings next to each other. Now I just wait for them to germinate and grow and bloom.
I use leaf mulch in much of my gardens and don't know if others listed self seed.