Alliums (Allium) repel aphids, cabbage worms, and slugs with their strong onion and sulfur scent. They thrive in USDA zones 3 to 9, needing full sunlight and well-drained soil to bloom in late spring to early summer.
Petunias (Petunia) not only add beauty but also deter insects. Ideal for USDA zones 10 and 11, they grow up to 18 inches tall and spread 4 feet wide, requiring ample water, sunlight, and sandy soil, blooming from spring through winter.
Marigolds (Tagetes spp.) help control nematode populations and are a fall favorite. Blooming from early summer to late fall, they need direct sunlight, loamy soil, and occasional watering. Suitable for USDA zones 2 to 11.
Floss flowers (Ageratum houstonianum) repel insects with their toxic compounds but can be harmful if ingested. Blooming mid-summer to fall, they grow up to 36 inches tall in USDA zones 2 to 11, needing full sunlight.
Lavender (Lavandula spp.) wards off mosquitoes with its linalool compound. Thriving in USDA zones 5 to 9, it requires full sun, well-drained, slightly acidic soil, and infrequent watering. It blooms from late spring to late fall.
Geraniums (Pelargonium) are effective against mosquitoes and beetles. Blooming from spring to fall, they need rich loam soil, plenty of sunlight, and can tolerate infrequent watering. Best suited for USDA zones 9 to 12.
Nasturtiums (Tropaeolum spp.) repel a variety of garden pests. Blooming summer to fall, they thrive in USDA zones 8 to 10, require direct sunlight, and loamy soil, and should be watered regularly but not excessively.