Marigold

Marigolds are susceptible to powdery mildew and spider mites. I suggest spraying them often with an organic fertilizer containing seaweed to keep spider mites away and keep some neem oil on hand just in case you see powdery mildew. 

These are worth the effort though! 

They are one of the most common companion plant for vegetable gardens. The flowers are edible. They produce a chemical that harms some nematodes (this is a good thing). Marigolds also attract pollinators and beneficial insects. Oh, and the deer don't like them! We're finally winning here!