Growing Sunflowers for Beginners
Are you looking to add something aesthetically appealing to your garden? Do you want something that attracts pollinators and is a good food source for animals and humans? If you answered yes to any of these, you should consider adding sunflowers to your garden. Sunflowers are a beautiful and versatile addition to any garden. They are one of the few crops that will meet both your ornamental and oilseed production needs.
Sunflowers can be grown from seeds and come in a variety of color patterns and sizes. Typically, sunflowers stand about 6 feet tall, but some varieties can grow anywhere from 2 to 15 feet tall. By utilizing succession plantings, you can harvest them throughout summer and fall.
Even though sunflowers are one of the only crops native to the United States, they didn’t become widely produced until the 1970s due to the demand of sunflower oil in Europe. The versatility of this crop allows it to thrive in a wide variety of soils and climates.
During the growing stages, young sunflower heads track the sun to absorb as much light as possible in a process called heliotropism. Once flowers become mature, the stem stiffens, and the sunflower heads will generally all face east.
Two types of sunflowers are typically grown – oilseed varieties and confection sunflowers. Oilseed sunflowers are grown for sunflower oil and bird seed. Sunflower oil is considered a healthy oil since it is low in saturated fats. Confection varieties are grown for human consumption, often in the form of roasted and baked seeds.
Sunflowers have extensive root systems that help them easily utilize soil nutrients. Sunflowers prefer well-drained soils with a pH between 6.0 to 7.0, like clay loam and silty clay soils. Test your soil to determine pH level and fertility needs before planting sunflowers.
Once the second set of leaves have appeared, a slow-release all-purpose fertilizer can be applied directly to the plants to speed up growth and produce larger flowers. Sunflowers also can benefit from applying half the recommended nitrogen during planting and the second half later in the growing season, which is known as a split application.
Sunflowers are annual plants that perform best in sunny locations. They can be easily started from seed by directly placing seeds into the ground. Sunflowers can also be started indoors as transplants, which allows for them to bloom earlier than direct seeding.
Plant sunflower seeds 1 to 2 inches deep after the last threat of frost. Space seeds 6 inches apart for smaller varieties and 12 inches apart for taller varieties. Once seedlings emerge, be sure to thin out as needed. Rows need to be spaced 2 to 3 feet apart.
Starting Seeds Indoors and Transplanting
It is best to plant seeds indoors in a controlled environment in biodegradable containers. Biodegradable pots allow the entire pot to be planted in the ground without disturbing the established root system. Before planting outdoors, the seedlings will need to be “hardened” to acclimate to the outdoor environment. One week prior to planting, place transplants outdoors in a safe location for a few hours. Each day, gradually increase the amount of time transplants spend outdoors. After several days, transplants should be spending 24 hours outdoors and will be ready to be planted into the ground once the threat of frost has passed.
Sunflower varieties typically reach maturity in 85 to 95 days. Consider using succession plantings to have sunflowers blooming throughout the entire growing season. Succession planting can be accomplished by planting the same variety of sunflowers every two to three weeks, planting different varieties with different maturity dates at the same time, or planting multiple varieties with multiple maturity dates every two to four weeks.
Sunflowers can handle warm temperatures and some drought, but they do need watered regularly to help create a strong root system during the beginning stages of growth. Sunflowers also need watered when applying fertilizer during the growing season to allow the fertilizer to move to the roots for uptake. Once plants have a strong start, sunflowers can be watered occasionally if there is no rain for several days. Sunflowers only require an inch of water a week.
Sunflowers can only outcompete weeds once they start to mature, therefore weed control is extremely important in the early stages of growth to allow plants to obtain nutrition and moisture. You can control weeds by tilling, hoeing, hand-pulling or applying mulch around the plants. You can also use herbicides to control weeds, but be sure to follow directions on the container label.
Disease and Insects
Although sunflowers are easy to grow, they can fall victim to wildlife, insects and diseases. When selecting your location, be sure to choose a spot that is safe from potential deer damage. Deer enjoy young sunflower plants and can demolish them quickly. Fencing or other deer repellents will need to be considered if planting them in an area with a high deer population.
Birds are another pest when growing sunflowers because they like to eat the seeds. They can be deterred by using spinners, scarecrows or owl decoys.
A few diseases, such as Alternaria and Phoma leaf spot, Rhizopus head rot, rust and white mold, can cause both yield and quality reduction of sunflower. In addition, powdery mildew and downy mildew can also appear on sunflowers at a later growth stage. Infection and spread of most of these diseases is favored by warm, humid conditions and extended periods of leaf wetness. Early planted fields are generally more susceptible to severe disease losses and may need measures against diseases. Cultural practices, such as rotation, deep plowing of crop residue and proper spacing, can reduce disease severity without a need for fungicide spray.
Insects can also be an issue when growing sunflowers. Since they are appealing to wildlife and insects, they are sometimes used as a “trap crop” to keep insects and pests away from other plants. Keep in mind that sunflowers also attract beneficial insects, such as bees and butterflies. When applying insecticides be sure to use caution and follow the label.
Eats plant stems, leaves and flowers.
Piercing and sucking mouthparts that can cause severe damage to plants and crops
Chewing mouthparts and can devour leaves and flower petals
Use slender needle-like mouthparts to feed on the sap from the plants. They are very common and can be found on most plants in gardens.
When the back of the sunflower seed head starts to turn brown, that is a sign that it’s time to harvest your sunflowers Combines are used to harvest large fields of sunflowers. There are specifically designed combine heads, or the regular “all crop” platform head is sufficient, but you can expect to have seed loss with an unmodified platform head. Some producers will modify the headers and install “catch pans” to help catch some of the seeds.
Home gardeners can harvest their sunflowers in the early morning to use for floral arrangements. Handle flowers carefully, and they can last in water at room temperature for up to a week. To harvest the seeds, you can either cut the flower heads off and let them dry and then remove the seeds or let them dry on the stem.
Sunflower seeds supply healthy unsaturated fats as well as magnesium, copper, manganese and vitamin E. One tablespoon of sunflower seeds contains 51 calories, 2 grams of protein, 4.5 grams of fat and 2 grams of carbs.
Daniels, P. (2018, October 02). Seeds are healthy sources of fiber. Retrieved March 22, 2021, from https://www.canr.msu.edu/news/seeds_are_healthy_sources_of_fiber
Trott, R. (2020). Sunflowers. Retrieved March 22, 2021, from https://extension.umn.edu/flowers/sunflowers#branching-cultivars-2103960
Westerfield, R. (2017, November 20). Growing Sunflowers in the Home Garden. Retrieved March 22, 2021, from https://extension.uga.edu/publications/detail.html?number=C1121&title=Growing+Sunflowers+in+the+Home+Garden
Last Reviewed: March 2022