Wouldn't we all like a bed where the flowers grow with no work from us and no weeds. It's a pipe dream.

There are plenty of annuals who drop seeds. They tend to fall where the wind blows them or around the mother plant. You may have a clump of them that are like hair on a dogs back, that have to be separated or they won't do anything and other spots with bare earth. Weeds will surely grow there.

How do you plan on enriching the soil? Plants can't grow forever in the same soil without some nutrients added once in a while.

Try it if you like but I don't think you'd be happy with the results

I have similar interests and am looking into annuals that can be sown in fall, and also Malcolmia, Matthiola, Layia, and Limnanthes which bloom quickly from seed, but I haven't grown them. I'm not sure how well they self-sow, though Limnanthes is possibly invasive, but is a California native adapted to growing in the wet season, which would make it nice for my PNW garden. Then there are always the very easy Nasturtiums, which come in lots of colors, sizes, and even variegated.

Flowers that self-sow well for me are usually problems, like particularly Forget-Me-Nots, though they are pretty for a while.

Since annuals are not around in the winter it is easy to add compost or organic matter to the soil then, or to blanket the area with mulch, newspaper, or cardboard to keep weeds from taking over in the winter. They would have to be removed before the growing season.

I have a blog where my main interest is in finding ways to discourage weeds.

Here is a link that might be useful: blog

hemnancy
You can add your organic matter in the fall, but don't expect selfsown seeds to come up from under it.

I guess the self-sown part is a problem, but only if you feel the need to fertilize. You could collect the seeds and mulch then sow them on top afterward, or collect and sow the next spring? Or just broadcast or sidedress fertilizer during the growing season. I'm not actually much for adding fertilizer, I just depend on the natural fertility of the soil and grow things that don't need it. I have clay loam, so it might be different for other soil; some plants like herbs and natives actually prefer poor soil. I grew some Clarkia and none self-sowed, I grew Nasturtiums and only a couple ever self-sowed. Lunaria does self-sow for me, and I like it a lot, but it doesn't come up in sheets or stay low. I also found out recently it has an edible root and leaves before blooming, and the seeds can be used to make mustard.

Anyway, I am going to try some of the annuals I mentioned hoping to find some good ground cover ones. Brrr, it seems like frost is near.

Nancy

If you want a list here's some self sowers here's some annuals that mainly come true to form.
Portulacca, Allyssum, Johny jump ups, Calendula, Dwarf Phlox, Snap dragons.

You are right that it is best to gather the seed and spread them where you would like them to grow.

Another tip --since these are all rather prolific selfseeders it is a good idea to deadhead for the first part of the season and let them go to seed near the end of the summer

Thanks, oilpainter. One article I saw said annuals rated HA could be sown in fall. I get nervous about any coming up and tend to start them under lights. This year I tried Emilia coccinea, some I planted under lights, some I sowed outdoors. The ones I started under lights Feb 12 I planted out May 7 and they started blooming June 26. They are a little tall, skimpy, and floppy, but still blooming, 1/2" red dandelion type flowers in clusters. They might look good mixed in with other plants of the same height that don't have a long bloom season. The direct sown didn't come up for a couple of months and then just started blooming in September. I will see what happens next year with fall planted ones.

Johnny Jump-ups did really well, I started them under lights Feb 12, some were blooming under lights by April 20. I planted them out May 8, they are still blooming and have already self-sown, some of those are just starting to bloom. They stay low and are really cute, too. I will see if they come back well next year.

An edible annual I grow is Corn Salad. It likes it cold, it comes up in October and grows all winter, the leaves are small, so hard to harvest, but they taste phenomenal. I use them kind of like a winter ground cover to keep down weeds. It seems to take forever for them to set seed in spring so I can plant something else, though. I don't collect the seed but they are great at self-sowing.

In S. Calif. Nasturtiums will self-sow to grow in winter too, down there they can get montrous over winter. Usually they died out in warm weather.

All the plants I listed have been grown in my garden in zone 3 and seed themselves and come up in the spring.

Johnny jump-ups no longer grow in my flower bed because they tended to take over. I guarantee they will be back next year.

One I missed is poppies.

You could start any of the ones I mentioned outside in very early spring or scatter them around before winter freeze. In fact depending on how cold it gets there they may be good winter flowers. A light frost won't hurt any of them

The dwarf Phlox would be in the Brassica family with the Malcolmia, Matthiola, Alyssum, Nasturtiums, and the natives Lunaria and Cheiranthus (Erysimum). I haven't grown some of them so can't compare, they all seem interesting, though I think I'm allergic to Alyssum because I sneeze when I'm around a lot of it. Anyone have experience with any others of these? They seem an interesting family, many are fragrant. I bought one Erysimum last year but killed it, apparently from overwatering. I'll have to try it in the ground. It had a wonderful fragrance. I know I will have to try some out next year, and try fall sowing some as well, though I'll probably start some from seed just to be sure.

French Marigolds were supposed to be planted in a certain area of my yard and fill a bed. After two years, there are no FM in that bed because the wind blows the seeds from that area; perhaps rodents like the seeds as well. But east of me, all the way down the street, I can see FM volunteers doing well!

So I agree that you should collect some seeds to direct sow where you want the plants.

Nigella will TAKE OVER. It's easy to pluck up the seedlings though.

Cosmos reseeded in my yard last year.

Borage also reseeds like mad.

I also prefer the self-seeding annuals, cottage gardening, but have found I need to have a perennial here and there to help with the weed control.

I have something like what the OP is asking having sowed a wildflower mixture where spring bulbs were planted. I don't know what the flowers are. The only problem is that some tend to take over and have to be culled out like weeds.

Many of the annual rudbeckia also self sow; so do some of the salvias and rose campion. As other people have indicated, the trick is to get the seed where you want it and not where you don't. Most of the annual seeds will get wind blown out of the bed the parents are in. That's nature's way of spreading to new areas that may still be fertile.

Many of the annual seeds also will rot or get eaten over a cold, especially wet winter, mulching will bury them or prevent good soil contact needed for high levels of germination, or they may just not ever drop into the bed you want them in.

Most of the annual seeds will not really thrive with fall direct sowing, although the biennials do. The best idea for annuals is to collect the seed from your plants in the fall in an envelope and stick them in your frig for the winter. In the early spring just before the bulbs emerge, clean off the bed, lightly scratch the surface, sprinkle the seeds and tamp a little to get good contact. You still have minimal work to seed, but the seed goes where you really want the plants and you won't have to weed them out of taking over other beds.

Do consider how thickly your bulb foliage may lie against the soil and block light and seed growth, like if you have a lot of daffodils in the bed.

KimKa