I have a bed in front of my house (part sun, northern exposure) where I've tried some annuals that are supposed to reseed (marigolds, sweet allysum, coreopsis, and something else I can't remember now), but nothing ever comes back. I'm wondering if there's something I should be doing to encourage them, short of collecting seeds & sowing them the next spring.
Don't know about the annuals you have, but I've had mixed luck with re-seeding miniature snapdragons. I let them die in the fall and don't touch them all winter. They are tiny tiny for the first few months (May-June), and it's tough to not pull them when you weed. You have to be careful where you tread, early in the spring. They do come up in masses, however -- so much that I need to thin them. They were evening growing in the cracks of my walkway. Where there wasn't much light, they don't grow fast. Some didn't bloom until mid September! Also, I'm in Montreal and the winters are hard and long.
There were some random portulaca that came back, which I didn't expect. My dill always comes back without any trouble -- but I let some of it go to seed for that reason.
This year, I am thinking it's worth it to go and buy the flowering annuals (already blooming in May) from a greenhouse -- only the Pansies/Violets seem to re-seed (biennial) and bloom early enough for my preference. It's a sense of accomplishment when the snapdragons do bloom from reseeding, but the summer-long wait for the flowers as well as the extra care with weeding doesn't seem worth it to me (anymore).
Cris Montreal Quebec
You will just need to buy new plants every year like everyone else who grows annuals.
It's a hit and miss thing. At my site, dianthus, asian lily, yarrow, and coneflower reseed well, but other flowers (including black-eyed susan, a relative of coneflower) don't. I know, only dianthus is an annual. Try a dozen annuals and go with what works. If you get four which reseed and have a somewhat staggered flowering schedule, you are home. Collecting seeds and starting them in flats works as well.
Do the annuals' seeds contact bare soil around your annuals? I wonder too, how many hours of sunlight you get with your northern exposure? The annuals that you listed generally do best in a sunny location.
Keep in mind that many self-seeding annuals can appear where you don't want them. I have had Cosmos (Cosmos sp.) and Lobularia maritima (sweet alyssum, sweet alison) self-seed between the interlocking stone pavers. Myosotis sylvatica (forget-me-not) and Calendula officinalis (pot marigold) are appearing in unexpected places too. Fortunately Iberis umbellata (candytuft) have been better behaved when self-seeding. I have all the above in a mixed sun/shade, except sweet alyssum which has mostly sun exposure.
If you go this self-seeding route, choose something like cosmos whose early seedlings are easily identified. Without a mulch to keep the weed seedlings down, there will be extra work weeding around your volunteers. Free plants can cost a lot of time.
Regards.
Actually that part of the bed gets more sun than the rest, so it's more like a full sun location. However, the bed's well-mulched, and that might be my problem. Perhaps the seeds never get to the soil.
Looks like the best bet will be to collect the seeds (or buy new) to start indoors.
Jacqueline Carmichaels PA
I have had impatiens, coleus, torenia, snapdragons, and alyssum re-seed. Of course they are rather late in appearing and often show up in small quantities and in places that aren't appreciated. If you use a lot of Preen, you will probably not get many volunteers.
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