Both chives (Alium schoenoprasum) and basil (Ocimum basilicum) produce chemicals that help repel some garden insects, such as aphids. Basil grows as an annual herb, while chives grow as perennials at U.S. Department of Agriculture plant hardiness zones 4 through 8. Companion putting these herbs with vegetables susceptible to insect damage and ornamental plants can help reduce pest damage.
Insects are repelled from the aromatic oils created by chives and basil. The smell of these herbs also confuses foraging insects, notes Cornell University’s extension, camouflaging the aroma of the plants that the insects wish to feed on. Blending chives and basil in using other plants or putting them as a border round insect-susceptible plants can provide some protection from pest insects.
Chives and basils make good companions for any plant that’s similar growing requirements, but perennial chives perform better if planted in an area where they won’t be disturbed each year. Chives also produce attractive lavender flowers, in addition to the deep green, grassy edible foliage, so they can make a suitable companion to ornamental perennials, such as roses (Rosa spp.) , which develop in USDA zones 4 through 9 depending on the variety. Basil works well with other annual plants. Although the green foliage is attractive, the plant is not highly ornamental so it makes a good companion to summer vegetables, such as tomatoes (Solanum lycopersicum) and peppers (Capsicum annuum).
Chives do best in mattresses that drain well with moderately rich soil. Chives tolerate both complete, all-day sun and partial shade, and that means you can companion plant them under or about bushes and larger plants that will filter the sun reaching the chives. They also grow well in clumps interspersed with vegetables, annual flowers or perennial flowers, but distance them 10 to 12 inches apart so you do not disturb the chives when replacing another plants. The plants can reach up to 18 inches tall when in flower, so they may not work well with lower growing flowers or flowers. Chives can withstand moist soil, but wet, soggy soil will kill them. They function best with about 1 inch of water each week. The flowers readily self-seed after flowering, so trim off the flower heads after blossom should youn’t want more plants.
Basil grows in warm, frost-free weather in beds that get complete, all-day sun. The plants can grow up to two feet tall, so space them about 12 inches away from their companion plants to prevent overcrowding. Basil needs moist dirt, usually about 1 inch of water a week is sufficient to keep the top 6 inches of soil moist. After flowering, basil plants begin to fall and perish. Pinching off the tips of the plants often to prevent flower buds from forming can expand their productiveness, or you’ll be able to replace the plants as soon as they begin to flower.