Different species of mycorrhizal fungus might cause a basil leaf to taste different or a strawberry plant to produce more delicious-looking berries. But how? Are some fungal partners “better” than others? Are some plant partners “better” than others? Can plants and fungi tell the difference between alternative partners? Decades have elapsed since Rayner’s remark, but we are only just beginning to understand the intricate behaviors that maintain a symbiotic balance between plants and mycorrhizal fungi.