Answer: Carnations bloom best in cool weather and perform best in rich, well-draining, loamy soil, in full sunshine. If your plants are producing buds which never open, I think upon closer inspection that you'll find a tiny hole in the unopened bud; evidence of bud worms. The little larvae feed on the insides of the bud before they exit. As a result, all the petals are gone and the bud never opens. There's no particular insecticide you can use because the pests are inside the bud where they're safe from predators and chemical sprays. Some years the problem is worse than others.
This spring, why not dig your plants out of the ground then amend the soil with some organic matter? Replant your carnations, wait a week or two for them to become established, then feed them every 3-4 weeks with a liquid fertilizer (Miracle Gro or Peter's). They should perk right up and begin blooming for you.
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