I have no idea....those cosmos are like weeds. I planted seeds when I first moved in here and now every year they pop up all over the place. As for my soil, some of it is coral rock after about an inch or two, some of my soil is closer to sand and some is okay. The cosmos grow everywhere. They seem to like spots with full sun as I've never seen them pop up in shade. Also watering I do nothing special, they get watered twice a week with my other plants. Are you planting the seeds? Maybe you should try just throwing them on top of the soil. that what I did. When they seeded I would just grab the head and then toss the seeds back in.

I can't grow them either and I start out with good looking plants from Lowes. Bad karma I guess.

Holy Cow I just pull em off the plant,
drop the seeds on the ground and I have Huge cosmos in no time. I have so many I must thin them and they come up in my yard too. Have you tried the orange?????They
seem to be the easiest.The others pinks and white seem to not be as hardy and I have had some come up but the orange out do em evey time!
These are the GIANT,they got way to carried away so I went to the regulars but some pop up each year.
tanya
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Hi seashore1,

I recently bought a couple of packets of the Burpee cosmic orange cosmos at HD and cleared out a planter next to my pool to sow the seeds. These things sprouted in 2 days!

All I did was add some cheap bags of top soil to the planter (adding to the existing poor sandy soil), a little bit of compost, and mix the top 1 ft or so. I planted them about .75" deep and covered them with a bit of dirt. I gently watered in the morning every day (and at night if the top layer of soil was dry). This planter is located in unrelenting full sun and probably heats up pretty quick during the day.

The cosmos just started growing their first set of true leaves, but I went out this morning to check on all my seedlings and noticed that many seedling leaves had been munched completely off!! :I hope that helps! :)

Maybe a salt issue? The only things that grow better from seed for me, up here in the panhandle, are crabgrass and yellow Oxalis. Maybe English Violets. I'd grow Early Cosmos in pots if I couldn't grow them in the ground. Seems to me first time I ever noticed a thumb that wasn't infected turning green was after a long afternoon deadheading Cosmos.

Tanya, those are the biggest cosmos I've ever seen. Are my eyes playing tricks on me or is that cosmos actually as tall as the eave of the house?? That's amazing.

I second that the orange ones are tougher. The purple/white/burgundy ones will grow but burn up much more quickly in the heat.

Bill

seashore, i have TONS of cosmos plants (and seeds) of ALL sizes if you'd like to try some 'homegrown' plants. in Central Brevard.... email me at Beth7Happy at cfl dot rr dot com

I toss the seeds on top of mulch and they grow easily. I did the same when I lived in Stuart. No idea why that works so well with some seeds (well, I have theories about how the ancestor plant propogated in the wild) but several things I plant do better that way that directly in soil.

Bill those were the Giants Cosmos and they WERE GIANT . My only complaint is that they grew and grew and grew all summer and didnt flower until fall. By then I thought something was wrong and had pulled a bunch . But I like the smaller more manageable ones,the flowers are the same size.
The grandkids thought they were magic beanstalks.

natives_and_veggies: "I toss the seeds on top of mulch and they grow easily...".

Maybe unrelated, but this reminded me of the old Amos Pettingill story about the volunteer Delphinium in the manure pile at White Flower Farm. Biggest Delphinium anyone around there had ever seen.

I think cosmos like lack of attention. I clear my bed and just toss some around and rake them in. Whenever I actually tried planting them with care I had complete failure.

Cosmos ARE dead easy - the only thing I can think (besides maybe the salt issue) is timing - I don't see WHEN you're planting them....?

I have found the Orange Klondike and Bright Lights that are a mixture of orange and yellow to grow the easiest. This year I have also gotten the Pink ones to grow from seed and I have some white ones doing okay so far. The pinks and whites do not reseed as easily for me. I have never had any luck keeping the plants from these colors alive if I buy them from a store. But for success - try the orange and yellow varieties. They do come in different heights and look really pretty with the native red saliva growing amongst them.

Maybe try them in pots then you can move them to different places to see where they do best. Perhaps the salt spray is a problem.

Cosmos need to be direct sown early in the Spring - Jan or Feb in zone 10 . Your page doesn't say what zone is yours .
I too have had something eliminate the tops of both cosmos and zinnia seedlings . Rabbits maybe ?

i want to thank each of you for taking the time to respond... this forum has some of the nicest people on it and i have learned so much over the years.

i think perhaps i was paying them too much attention... as in planting each see individually then watering, hovering, etc.

i will try some of the tips here and see how it goes... as of this morning, i have 5 tiny seedlings emerging from the soil so perhaps all of your nice thoughts just erased some of my bad cosmos karma. :)

thanks again for your time and happy gardening!

p.s. to show my gratitude, i wish rain on all of us as i think we could all use some in this heat! :)

Those Mexican Cosmos are by far the easiest as they can be started any season. Other cosmos should be started in the fall to get established to bloom in the early spring this far south.

I have the same problem!

The only reason I can think of is like RSTanny said - salt? Do you live near the shore? I too love the orange best and have been growing them up north and down here from seed I started collecting about 30 years ago. Good luck to you.

The seeds kinda need to stay at least a little damp while germinating. If I can make sure that happens then they grow easily. My problem is the chickens see me putting seeds in the ground, they think its treats and come scratch them up and eat them. I have to either fence them off or start them in peat pods and transplant them.

sultry_jasmine_nights (Florida 9a) I am wanting to grow cosmmos here in South Florida. I know they grow here, because on my way to Costco I see a huge bed with nothing but cosmos and zinnias....... I tried putting down seed outside on the ground and nada. Three weeks later nothing has come up. I followed the directions. Not sure what happeded..... can you tell me how you start them in peat pods. Unfortunately, I never seem to grow anything in a peat pod, they dry out too fast, so the seed doesn't stay damp..... how do you do it..... thanks.

Sharon