Answer: I'm not aware of any allelopathic (chemical warfare) traits in rosemary. It's generally grown with other plants, especially in mixed herb beds. Perhaps the companion plants you've chosen for the bed do not thrive in the full sunshine and dry soils that suit rosemary. Try growing portulaca, salvia, artemisia, coreopsis, euphorbia, gaillardia, oenothera, marigold, zinnia, liatris and linum in the bed with your rosemary.
Hope you have a colorful summer!
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