By Hjr
United Kingdom 
Hope someone can help me here! I have a coreopsis that was doing beautifully until I repotted it 2 weeks ago. At the same time I bought 3 new ones (different variety) & repotted them too. All of them are now producing flowers that turn brown & dry up before they're fully open. The original one also has mildew looking pallid leaves. At the same time I repotted scabiosas (also newly purchased) & their flowers are no longer thriving either. At first I thought this might be due to fruit & veg food granules I'd mixed with the compost (I was told this would promote better flowering), but have since changed all the compost again, & the problem persist. I'm using a general purpose compost that I've never had a problem
with before, & they all get plenty of water & sun. Would be grateful for any advice, as I've spent so much money on them all, & the original coreopsis was my pride & joy!!!
10 Jul, 2017
Hi, welcome to GoY, there are 80 - 100 species of Coreopsis, the species usually grown in the U K are hardy, and should be planted in the ground in an annual or herbaceous border, is there a particular reason why you have them in pots ?, it's usually the more tender species that are 'sometimes' kept in pots.
where do you keep the pots ? in the border they can be grown in full sun or partial shade, but in pots they may need more watering , than they would if planted out, the same also applies to the Scabiosa, but this should be grown in full sun, Derek.
10 Jul, 2017