What methods have you tried? Cleome needs stratification. The seeds need to be surface sown and just patted to insure that the seeds are in contact with the soil. It needs light to germinate. Water from the bottom so as not to wash the seeds off. Putting the tray in a plastic bag will help the humidity. You should get germination in about 10 to 14 days. If you still haven't gotten germination, try another session of cold.
Winter sowing will do all this naturally for you.
Carole

I have tried ward sowing a couple times and winter sowing. Infact I can see the little seeds still sitting on top of the soild in the milk carton. It has not dried out at all, in fact if anything its been too wet, but the carton does have good drainage. Maybe I will try refrigerating them first this time. I really just want to see them in the garden. I thought they were "weeds". Oh well, I will keep trying.

I too saved seeds from cleomes in the garden and put them in potting soil, under soil. They sprouted - no cold period or anything. They did take awhile, it was at least 2 weeks before they popped out, but all did.

I'll keep checking the milk jug every day and I'll also try in pots. Wish me luck...

Yes, they are generally easy to germinate, but they do like a variation in day and night temperature. Last year I started some off in a heated propagator and nothing happened. Then I took them out of the propagator so they were exposed to normal fluctuations in temperatures... and they germinated.

I've only started them once - from a GW trade, using Winter Sowing in a couple gallon nursery pots, covered & set outside in bright shade. Had lots of starts - and was a bit freaked out at first since they looked like marijuana!

People said they'd self sow wildly, so I dead-headed too agressively, and assumed I'd still get some from seeds I missed. Didn't see any however - so I'm going WS again this season...and be sure to leave a few seed heads in place to self-sow this time. I liked the tall mass I grew with california Zinnia. It made a section of my backyard garden really lush - at least for one season.

I looked cleome up in my seed germination data base and the instructions are to direct sow in the fall or provide oscillating temperatures- 80 day/70 night. I guess you have to sow them outside to get the swing.
A lot of the South African seeds I buy are like that. . They will not germinate under steady temperatures. I wonder if cleome is native to South Africa.
Whoa Nellie. I looked at the Thompson-Morgan database and they say stratify and surface sow .( usually light is a trigger for stratified seeds). Based on what Ornata says, oscillation does work so perhaps both techniques are valid.

YAY YAY YAY! Well after hearing about the temp variations needed I tried aomething different. I took my WS jug inside and sat it on the radiator set on low. It went on and off for about a week, but when I still didn't see anything, I stuck it outside again. Well HOORAY! I saw one sprout today!!! I am hoping to get more soon!
I Still plan to sow some more soon to see what happens.

over a year later, i nicole have found cleomes....... now i live in 9b and was wondering IF i can plant these NOW, in september or wait til spring......... You would think i would understand by reading the above posts, but no..... i can be thick headed.
Nicole

Nicle, these aren't frost hardy, so seedlings may germinate now only to be lost this winter if your temperature does drop below freezing. Perfect timing for outdoor sowing would be to sow while your nights are in the low 40's, a couple of weeks before the last possibility of any frost in your area. If no frost shows up, that's fine. They don't need freezing, just cool, moist, 40ish degrees for a couple of weeks before warming up some.