Sunflowers should be planted 1 to 1 1/2 inches deep. Row spacing studies have shown that sunflowers do not yield better in narrow rows, whereas wide rows are preferable to allow cultivating for weeds or use a row crop header. Sunflowers are not particularly sensitive to seeding rate, since head size (and seed number) per plant will increase in a thinner stand. Seeding rates can be from 15,000 to 25,000 plants per acre. Sunflower seeds vary in size, so seeding rate based on weight must take into account seed size, but will be roughly 3 to 4 pounds per acre. Number 2 sunflower seeds are largest, while number 5 are smallest. Most sunflower seed available is sized as a 3 or 4. Size of the seed can affect what type of planter modifications are necessary, such as buying new seed plates or finger pickups.
Planting sunflower can begin anytime after soils have warmed to 50 degrees F. (April) through mid-July. It’s not a bad idea to plant sunflower on a couple of different dates to reduce risk and spread out labor load. Planting early can allow sunflower to be harvested before corn and soybeans, and will likely avoid any bird damage. Planting late can allow planting after other crops are done, and is less likely to have damage from sunflower moth. Double crop planting after wheat works well with sunflower, and can be done in the northern part of Missouri since sunflower is more frost tolerant than soybeans in the fall.
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