Companion planting is the art and science of planting different types on plants in close proximity to each other in order to create a mutually beneficial relationship between the two. Some plants will emit an aroma that wards off harmful insects while other will send a chemical signal that attracts beneficial ones. Plants that give off nutrients do well when placed by heavy feeders while tall plants, such as sunflowers, can provide shade and support for those that grow low to the ground.
Start planning and planting early. Sunflowers take approximately 70 to 100 days to mature, so they are best begun in the spring after all threat of frost has passed.
Determine what benefit you'd like to derive from companion planting. Sunflowers can be advantageous to a garden in many ways.
Get rid of aphids by placing sunflowers near plants which are likely to attract them, such as roses or tomatoes. The bright blossoms draw ladybugs and ants, both of which feed on aphids. As an added bonus, sunflowers also draw in hummingbirds, which dine on soft-bodied insects such as mosquitoes and white flies.
Provide support for vines such as cucumbers by planting them near sunflowers and then training the vines to climb up the sunflower stalks.
Create shade for less heat-tolerant plants, such as lettuce, by placing seeds around the base of sunflower stalks.
Select planting sites that receive full sun and prepare the soil at each site by adding enrichments such as compost or well-rotted manure.
Sow the seeds, placing five or six seeds in a small clump approximately 1 inch below ground. Leave at least 18 inches between clumps and then water the newly planted seeds. Pay close attention to the spacing of the sunflowers. Putting the plants too close together will result in weak, spindly stalks.
Keep the soil at the planting site moist and within 10 days seedlings should emerge. Allow the plants to grow several inches in height and then thin each to three plants.
Allow the plants to continue to grow. When they are approximately one foot tall, thin each clump to two plants; when the sunflowers reach two feet in height, thin clumps to a single plant.
Fertilize and water your sunflowers about once a week. They are heavy feeders which rapidly drain the soil of nutrients.