The Q&A Archives: No Blooms on mature cosmos

Question: I planted cosmos in March in my cold frame. After transplanting in May, all are doing well except for the yellow. Not one plant from the yellow packet (rare yellow cosmos was what the packet stated) has set even a bud let alone a bloom. They are all about two feet tall, very bushy and other wise very healthy. I have fertilized them "plant starter" then "plant tone", and I have watered them. What can I do to get them to bloom? Will they bloom? I hear sometimes hybirds don't produce blooms. Should I yank them and start over with something else, even though it's probably too late in the season for anything to be started.

Answer: Although I am not certain which cosmos you are growing, there are several possible explanations. It may be that this variety needs a longer growing season because it simply requires more maturity to bloom than the other cosmos we normally grow as annuals. This might explain why it is rare. It may simply be a shy bloomer, which again would explain why it is rare. It may be that it has too little light or too much nitrogen (this will cause lots of foliage and fewer blooms). It may be that it is actually a perennial variety of cosmos and will not bloom until next year. If you have the space, you might leave them there and just wait and see what happens.

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