What Not to Grow With Chrysanthemums
The one plant not to grow with chrysanthemums is more chrysanthemums. Mums are susceptible to aphids and mildew so they do much better in a mixed flower bed than in a mass planting.
It’s best to divide and move the mums in the spring every few years to prevent disease and pest problems. Remove any dead or diseased parts and replant the divisions in loose, well-drained soil in a sunny location.