Annual rudbeckias, feverfew, alyssum, larkspur, nigella, marigolds, portulaca, amaranthus, celosia, snapdragons, poppies, chinese asters (gorgeous, IMO!) morning glories, and sunflowers all reseed for me, off the top of my head.

Some perennials that reseed for me are echinacea, columbines, knautia, campanula (can't remember which ones I have...) and perennial foxgloves. Oh yeah, biennial foxgloves reseed too!

Good luck, and just be careful what you wish for, lol. Sometimes these things can get out of hand if you are not careful!

Dee

I tend to sort reseeders into problem reseeders and delightful ones, though I may have different results since I am a zone and a half north of you. Problem reseeders have tenacious roots that make them difficult to remove from where they are unwanted and/or produce a large amount of viable seed so that regular deadheading is a must. Delightful reseeders are easy to remove from unwanted areas and I can prevent reseeding by putting down mulch.

Delightful reseeders:
annuals and biennials: Nicotiana/flowering tobacco, Verbena bonarensis, Johnny jump-ups, annual poppies, foxglove

perennials: balloon flowers, columbines

Problem reseeders:
annuals and biennials: Foreget-me-nots
perennials: Valerian officianalis, Joe-Pye-weed, Lobelia siphilitica, Gypsophila/baby's breath, tall phlox

I like that classification babs!

To the delightful list I will add cosmos and sweet William.

I have a large yard and garden, many areas bordering on woodland. Things that many people consider problem reseeders, I don't mind in these area. I have lots of rudbeckia, Rose campion, morning glories, yellow primrose, obedient plant in those areas (though the last 2 spread by runner roots more than by reseeding).

So anything that is known as a vigorous reseeders ask yourself the question - how would I feel if this plant took over 75% of my garden bed?

I'll lend my voice to the above posts but add this cautionary note: check the Massachusetts list of invasive species before you plant what may become something that, in the years ahead, you wish you'd never heard of. Google common plant names so you can verify the botanical name which will allow you to make informed decisions about what to plant and not later regret.

Don't rely on seed sources or garden nurseries to NOT sell aggressive or invasive plants or on landscape designers to exclude them from garden plans.

Just words of caution from an experienced gardener.

Here is a link that might be useful: Invasive Species List - Mass.Org