Answer: Your side-by-side mums are each expressing their own individuality. There are about 160 species of chrysanthemums, and most adhere to the natural bloom cycle of the autumn months. Some of the newer hybrids bloom during the summer months instead. Since you've given both the same care and one is not blooming yet, I expect you are growing C. morifolium, the autumn blooming mum, and C. carinatum, the summer blooming mum. C. morifolium should have developed flower buds by now, so watch carefully for them and remove some of the buds from each cluster to promote larger (but fewer) flowers.
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