I just don't fertilize those plants that don't need it. I don't have any problems with cosmos blooming in ammended soil.

Sierra

I just throw the seeds where I want them and they grow and bloom all summer, wherever they grow.
They ain't picky!
Annie

I was actually thinking of asking a similar question about doing a no amendments bed and asking which flowers would be good candidates for such a bed. Cosmos, Nasturtiums and Cleome were on my list. Are there others that would be better off in average soil?

I don't amend my soil -do make compost (tea) and water all the plants. My soil is black sandy loam. And the cosmos bloom. Plan on planting more of them +lots of zinnias. to mix in with other plants.

Laura, you can add yarrow and gaillardia to your list.

Libby

Last spring/summer I helped out in the Plant a Row for the Hungry garden maintained by our Master Gardening class. You can be sure the soil has been very well amended over the years, and yet the cosmos volunteers that came up here and there had an abundance of flowers.

Diane

Laura, I think that a lot of us have had cosmos that were nothing but jolly green giants with no blooms at all. Research I've read says that a big reason for that is because cosmos needs short-days to bloom well. If they're started early enough, they will bloom in late spring, and keep on blooming through the summer. But, if they are just hitting their stride in the long days of June and July, they will refuse to bloom much, if at all, until later when the days get shorter. I don't really know how important the fertility issue is.

ThinMan

Here is a link that might be useful: Short-Day Bloomers

I sow and resow Cosmos seed on my property from Spring thru Summer and they all grow and bloom profusely clear up till first hard freeze.
I have no answer for you.
Annie

Last year the cosmos got totally out of control. I mean....frightening! This year I'm going to plant some of the pink ones - NOT the orange kind! But I'm going to restrict them to a bed along the driveway. WAAAAAAAAAAAY over there! (Get out of my regular beds.)

They went nuts. Four to five feet tall....scrawny but flowery. Pushing everything else out of the way. You couldn't cut 'em down but you didn't want 'em to live...

Good grief!

My gardens get that way with Bachelor Buttons. They reseed like crazy and show up everywhere. Beautiful, but pesky because they take over & then later they flop over.
Annie

This is my favorite cosmos, called Psycho White Cosmos. The flower is more sturdy and full than other cosmos.

{{gwi:643170}}
Lorna

Nice, Lorna. Maybe I'd better try to pick up a seed packet of those. I like 'em!

ThinMan

Thanks everybody!

I'm just going to plant them and not worry about it. I think there may be a lot in what ThinMan said in his post because I've had volunteer cosmos that bloomed their fool heads off; and then I've had others that I started from seed in spring indoors that finally bloomed in July but without the vigor of the self sown plants.

So now I'm crossing my fingers that my wintersown varieties will sprout/bloom earlier than later.

Thanks again!

I love cosmos and they don't love me back :-( Don't know the reason, I always direct sow in different parts of the garden but hardly any come up. Those that do are usually immediately mowed down to the ground by slugs and snails, sigh... I certainly do not have over fertile soil, so that cannot possibly be the reason for their demise.

Eduarda, trying again this year