Sunflowers & Their Soil

Soil Preparation

• Ready the soil before planting sunflower seeds to make it fertile and able to support tender young seedlings. Washington State University suggestions mixing manure or compost into the soil to infuse it with nutrients and minerals necessary for healthy sunflowers. More fertilizer can be added as the plants grow, but only small amounts, as too much causes few blossoms and weak stems. Also, ensure the planting location is well-drained, as poorly drained soil will stunt the flowers' growth.

Spacing and Planting

• Space sunflowers seeds properly to get large, healthy flowers. The University of California at Davis recommends planting varieties that are 2 to 5 feet tall at least 6 inches apart. Taller sunflowers should be given a foot of space between each plant and giant sunflowers, which can grow over 10 feet tall, require 2 feet of room to avoid crowding. Bury the seeds under an inch of soil.

Mulching

• Mulching sunflowers benefits the soil in several ways, leading to stronger, healthier plants. Spread a layer of organic mulch around the sunflowers to reduce the loss of moisture in the soil through evaporation, keeping the plants hydrated. Mulch also discourages the growth of weeds and helps keep the soil cool. As organic mulch decomposes, it naturally enriches the soil with minerals and nutrients and reduces the amount of extra waterings needed. Shredded bark, straw, chopped leaves and and wood chips all make excellent mulch.

Watering

• Keep the soil surrounding sunflowers moist, as the thirsty plants require proper hydration to thrive. The most important growth period for sunflowers occurs 20 days before and after flowering. Well-mulched soil high in organic content needs watering only if a week or pass without rain. Poorer quality soil may need daily watering, however. Deeply watering sunflowers also encourages strong roots, which is particularly important given the heavy weight of the flowerheads.