Cosmos all over the place. Easy to pull out though. Cleome has never re-seeded for me. I love it but it needs to be planted away from living quarters! It really does stink.

I never noticed cleome stink! I grew some dwarf ones last year and have violet queen (from seed) this year. I never get too close to it because its in a sort of odd location, though. I love them, though, I might need to go smell them later this evening... :-/

Ken - if you have some secret trick for getting rid of the violas let me know. I'll try anything... I've been constantly trying to get rid of these. All though now I probably shouldn't... in some spots they're all the lawn I have left :(

i use a lot of roundup generic.. all over my 5 acres ....

learning what things look like in spring.. is the only trick to eradicating such .... along with persistence, of course ...

ken

Grandpa Ott's Morning Glory - re-seeds like crazy, and if I let them grow in the wrong place they choke out anything in their way. I was warned about them, but didnt listen. Pretty much nothing else reseeds much in my garden, and I assumed it would be the same for these - wrong.

Cleome, yes, due to the skunk smell as well. My wife likes johnny-jump-ups, so I keep some. Purple basil got waaay out of hand, but I've since corralled it. Almost let feverfew get the best of me, but its all but gone now. Alliums are next on my list and then that Italian heirloom arugula and garlic chives and...

tj

Hands down , it's plume celosia!....They will reseed with a
passion!......but when the next season rolls around.....if
I plan on planting another kind of flower in their place, they
are very simple to weed out with my hoe.
I do love to grow the crested celosia (aka cockscombs).

carol

Portulaca in gravel mulch. It comes up by the zillions in a big green succulent patch and its hard to weed out because its a solid mass of green that is slimy and tedious to pull up the next year anywhere you had a single plant the year before. Each plant must make a million seeds each and each one must come up. It wants to be grass turf the next year. There's more waiting to germinate after you weed out the first batch. Its probably no problem where you can get a hoe to it, but I don't ever plant it in gravel anymore.

Red Amaranth. Don't ever leave the seed heads on this. You will even have them coming up in the cracks of your street and sidewalk and all through your lawn. They will survive and grow well in a small crack if you want one growing in your street.

Any type of annual ornamental grass. If you really want a mess to weed out, add any variety of Love Grass and you will really be in for it. Those form deep roots pretty early on.

I grew some kind of agastache from seed a few years ago...little did I know it would seed itself all over the place...took 2 seasons to weed out-yuck.

Definitely giant red celosia...but I love it so much I leave a few of the biggest, healthiest seedlings to mature. The rest get composted. I got the original plants from seed I took from street planters in Cooperstown, NY. They were HUGE plants, very impressive.

Corydalis. It's all over the place including cracks in the cement. I haven't pulled it out yet because it's making an impenetrable ground cover with non-stop yellow flowers. But I see the time approaching very soon.

Ruellia. It took years to get rid of. Ditto for Red Cypress Vine: duh. It's in the morning glory family, but I didn't know that. So, let me just mention that all the ipomeas I have ever planted were time bombs, except for moon vine.
Pink achillea. Spreads by seeds AND runners. Ugh.
Celosia, as listed above. Cocks Comb is just as bad.
Cleome only comes up modestly through my heavy mulching here. I rather like it in moderation.

All in all, though, I think that reseeders are far easier to deal with than the kind of plants that spread by root runners. At least with reseeders you usually don't have to get every little speck of root as long as you keep it from setting seed again. Beware Illustris Elephant Ears!!!

Cleome seedlings. I have to be aggressive in cutting the pods before they open.

I'm having serious thoughts about shade gardening, at least my current/original plan, in one spot in my yard, and would like to leave the aggressive and tree sprouts behind. I've never had any 'flower' plant reseed to the point where it had to all go, but spend countless hours every year pulling tree seedlings. Most less-sturdy unwanted sprouts come up easily, or are damaged beyond redemption by stepping on them/hoeing/raking, just pulling their tops off, a new layer of mulch, easy measures, but trees will not stop if merely beheaded or covered in a little more mulch, and don't come up easily.

I'm going to make that a requirement for any new garden areas - they can't be under a seed-dropping tree. The mulch conditions that prevent most 'weed' seeds from sprouting are exactly what tree seeds adore.

Morning Glories mostly the purplish one...Way out there this year. next year-plucking or hoeing-start over with fresh mg seed. I don't think the other colors came back in troves like they did. The ones left on purpose were huge stemmed and a bit aggressive!

Sweet Allysum. Why, o why did I ever scatter those first seeds???

Birds drive me crazy by planting sunflowers everywhere.
Poppies. Geez how many seeds can one plant make???
Bachelor buttons are tough to pull.
Those Johnny-jump-ups are a pain too, but somehow still so darling.

One thing that I have learned is if they are that invasive then they become boarder plants that do not need to be watched. But even then many of them I find homes for later on. Here in the Houston are we have spider plants, Mexican petunia, dwarf and standard, Cypress vine, Paper white daffodils, wild iris that will run all over a flower bed. But so far friends and neighbors have taken many of them off my hands when they take up too much room. As for Cleome they do not even reseed here without a lot of help. Those hundred plus seeds have not even tried to re-sprout so far.

Good luck on eradicating Johnny jump ups. I planted them 35 years ago. I don't have any in my flower beds and for the most part they are gone but every once in a while 1 will pop up somewhere in the yard. Just last year I found one growing in the vegetable garden. How it got there I don't know. Occasionally they show up in the lawn. Of course they are pulled as soon as they are spotted but I can't say they are 100% eradicated. They have to be the worst weedy flower there is.

Lily of the valley is another pest that I managed to get rid of with a lot of digging and pulling as soon as it reared it's head. It took me 3 years to get them all.

A plant that reseeds a lot in my garden is Verbena bonariensis but I'm not leaving it behind because it attracts a lot of butterflies to the garden. Every spring so many seedlings come up, it can get annoying. Luckily they are easily pulled out. I've given seed to people who garden on clay soil and they can hardly keep the plant alive for more than a summer season.

Strange to read that Cleome hasleriana reseeds so prolifically in many American gardens. Sometimes I see a few seedlings in my garden (if I'm lucky).

Ruellia (thank goodness 99.9% are the dwarf type.)
Four o'clock (constant battle...had them one year, have been pulling seedlings for 4 years)
Maximilian sunflower (perennial sunflower)

For me, the reseeders I weeded out are cleome (yes, rabbits on crack) and nicotiana.

I'm about to plant annual poppies for the first time and I hear I will never be rid of those.

The garden club is usually happy to have reseeding. You would n't believe the beautiful alyssum we have hanging a foot or more over the edge of some planters. And we don't have to buy as many flowers so we love that and just move the seedlings around. The one plant that came back with a vengeance after we didn't want it was Bells of Ireland. Although they are lovely close up, they just didn't look right in our design. However we got seedlings for a decade! The ones at my house never came back :(. We also got a lawn in one of the perennial beds from a perennial grass.

Annuals don't reseed at my house, but I wish someone had warned me about certain perennials: pulmonaria (lungwort) which is now everywhere. Also that pretty weedy campanula. I don't know how it got in the garden, but the roots are 2 feet down and enormous! Thank goodness for roundup. And an anenome that is native here and just lovely - white flowers nodding in the breeze and pretty foliage for the first 4 or 5 years then suddenly it is everywhere with a thick network of hairy roots, and it doesn't look nice when it goes by either. For shrubs, certain spireas seed everywhere.

My primula vera self seed, but i like that.

Kathy

Perennial geranium is my monster. It's beautiful when it first blooms, but then gets hit by tarnish beetles and isn't pretty anymore. Plus it flops over and sprawls unattractively.