How To Grow And Care For Sunflowers

Cheerful sunflowers (Helianthus annuus) are classic, bright blooms that emerge throughout the summer, making impressive cut flowers and attracting pollinators. These annual plants, native to North America, are highly recognizable for their large petals and flower shapes. Most commonly known for the tall, sun-yellow variety, sunflowers are available in various colors and sizes. Blooms can be red, chocolate, peach, lemon, or burgundy. You can even buy multicolored selections.

Depending on the variety, mature sunflowers grow to nearly 10 feet tall with minimal maintenance requirements. Sunflowers are heliotropic, meaning the young flowers grow with their face to the sun, returning the an easterly position at night. This occurs only in young flowers-- the mature flowers only face east. The flower os a sunflower is actually a pseudanthium, or flowerhead, made up of many small flowers. The outer petals are known as ray flowers and are made up of multiple petals fused together. The black-brown flowers in the center of the head, called disk flowers, grow in a spiral formation and mature into sunflower seeds when pollinated by bees. While not invasive in all areas, the self-seeding nature of sunflowers can allow these flowers to spread if left unchecked. Additionally, because of their tall stems, sunflowers are susceptible to breaking in strong winds, so choose an area with some protection from the weather.

Plant Attributes

Sunflower Care

Sunflowers are low-maintenance and drought-tolerant flowers that grow in most soil conditions. Provide flowers with plenty of daily sunlight, whether in a garden or containers, for at least six to eight hours. If growing sunflowers in a container, provide enough drainage and loose soil. 

As sun-loving plants, wait until the last frost passes to plant seeds. These flowers need fertile, nutrient-rich soil that does not remain wet. Well-draining soil is critical for flourishing blooms. Sunflowers are susceptible to squirrels, rabbits, and other wildlife that enjoy eating these plants, so using a protective netting or cage can help avoid unwanted pests.

Light

Sunflowers love daily sunlight—at least six to eight hours. Regions with long, warm summers have ample blooms with healthy, sturdy stems because of the plant's heliotropic nature.

Soil

Plant seeds in fertile, well-drained soil either in the ground or in raised beds. Pick a spot where your flowers receive full sun and where you can water easily. It's necessary to till or double dig the soil surrounding sunflowers before planting to soften the ground and remove roots or rocks. Sunflowers dislike competing for space, so avoid weed growth where possible. While sunflowers will grow in loamy, clay, or sandy soils, they need a well-draining area for healthiest growth.

Water

Sunflowers are relatively drought-tolerant but are healthiest when receiving regular watering—water younger plants around the roots. Use your hands to feel if the top few inches of soil are dry to know when to water plants. Also, sunflower heads will droop if they do not receive enough water. Established plants need watering about once a week, depending on rainfall in the region.

Temperature and Humidity

Sunflowers tolerate a range of temperatures. Plant in an area with proper air circulation, but don't expose tall stems to windy conditions. These flowers thrive in moderately warm climates. As long as sunflowers have routine care, these flowers can tolerate excessive heat and humidity. Waiting until after the last frost is crucial for successful planting.

Fertilizer

Sunflowers require nutrient-rich soil, so amend the growing area with organic matter or compost to match their heavy-feeding growth habits. Slow-release fertilizer containing nitrogen, phosphorus, and potassium is best when planted about eight inches deep in the soil during the spring. Sunflowers have expansive root systems that can acquire moisture from deep within the ground. Refrain from overfertilizing plants or fertilizing near the plant's base because it will cause the flower heads to droop or fall off.

Types of Sunflowers

Sunflowers are available in a variety of sizes and colors. Here are some sunflower species:

• 'Mammoth' (Helianthus giganteus): This traditional, drought-tolerant sunflower grows above 12 feet tall, attracting pollinators like birds. 
• 'Autumn Beauty' (Helianthus annuus): In a mixture of orange, red, and yellow, this sunflower variety appears in the late summer season and extends to the fall. The showy, nectar-rich blooms attract butterflies and hummingbirds.
• 'Teddy Bear' (Helianthus annuus): Ideal for container gardens or cut flowers, this sunflower reaches two to three feet and contains gold blossoms.
  

Propagating Sunflowers

Annual sunflowers should but grown from seed, not cuttings. However, perennial sunflowers can be grown from cuttings. Propagating perennial sunflowers from cuttings is more challenging than from seed, but different varieties require different methods. It's still possible to propagate sunflowers through cuttings, so here is how you would do it: 

1. Choose a four-to-six-inch stem with mature leaves and no flower buds. Use a sharp knife or pruning shears to select cuttings in the morning in spring.
2. Remove all but two or three leaves, exposing the nodes. Cut off the top half-inch of the stem.
3. Dip cuttings into a rooting hormone if desired. 
4. Plant the leafless section of the cutting in a potting mixture filled with half sand and half peat moss. 
5. Move cuttings to a warm area with indirect sunlight. Keep the entire planted cuttings covered to help insulate the humidity. 
6. After two to four weeks, roots should emerge and can transplant outdoors. Test for roots by gently tugging on the cuttings to feel for resistance. 
7. Expose cuttings to more direct sunlight daily until the plant can tolerate full sun.
   

How to Grow Sunflowers From Seed

After the final frost passes, sow sunflowers directly into the garden during the spring. Depending on your area, start sunflowers indoors to help prevent an unexpected cold snap from harming the seeds. If starting indoors, begin the process about three or four weeks before growing from seeds directly sown in the garden. Use biodegradable containers that can be directly planted in the garden, as sunflowers dislike root disturbance.

Purchase seeds at a garden center or harvest from existing sunflower plants. Let sunflower heads fully mature--allowing the seeds to ripen and dry on the stem—until it turns brown and the foliage is yellow. The seeds should appear somewhat loose. Keep the drying flower away from birds so they don't remove the seeds before you can. When ready, cut about six inches below the sunflower head and place the sunflower heads flat in a container to keep the fallen or loose seeds. If the seeds stay in place, remove your hand or gently use a tool to slide the seeds away from the flower head. You can also place the sunflower head into a pillowcase, closing the end with a rubber band, and "thresh" the head--hitting it against a rock or with a rolling pin to loosen the seeds. Separate the seeds from the debris, and place on a paper plate to dry thoroughly. Place seeds in a paper envelope, labeled with harvest date and varietal name. Store seeds in a cool, dark, dry location until the following spring. 

Start by spacing seeds about eight inches apart and one-half of an inch deep. Depending on the selection, the time between sowing and blooming is around 50 to 70 days. Keep the soil moist and not soggy until plants establish and sprout. Sunflowers bloom for about three weeks.

Overwintering

As annuals, sunflowers do not require much winter care because they die after flowering and seeding, meaning you will need to sow seeds again the following spring. Mulching around the sunflower garden bed is also not required.

Common Pests & Plant Diseases

Sunflowers attract pollinators, but these flowers also attract birds, rodents, deer, and pests. Protective barriers or netting can prevent animals from eating these flowers. Pests, including sunflower moths, beetles, caterpillars, weevils, and gray moths, are found on these plants but use insecticides sparingly because they can be harmful to beneficial insects. Try removing pests with your hands and only use an insecticide spray if more damage is done, like significant holes from bite marks. 

Diseases such as powdery mildew, rust, rot, and Verticillium wilt can occur if the sunflowers are overcrowded and not receiving enough air circulation or well-draining soil. Use a garden fungicide spray at the first sign of these diseases to prevent them from spreading.

Common Problems With Sunflowers

Sunflowers are more susceptible to disease when mismanaging the growing environment or care instructions. These relatively easy-to-grow flowers still have some problems to be aware of that signify disease.

Leaves Turning Black/Brown

Without proper water balance, sunflowers can develop fungal wilting. This soil-borne disease appears in underwatered sunflowers causing dark brown spots on the foliage and stem. If left untreated, the infection will continue to spread, but if the wilting and spots stop spreading after a few days of water maintenance, that is likely the cause. If the problem persists, the soil in the growing area might be compromised, so you need to move plants to a new location. 

Leaves Turning Yellow

Too much water causes sunflower foliage to turn yellow. Sunflowers do not thrive in wet areas—plant in a well-draining area and only water sunflowers when the top few inches of soil are dry. Consider rainfall when watering sunflowers because their expensive root system allows them to access moisture. Additionally, improper nutrient balance can cause yellowing leaves. Add a nitrogen-based fertilizer to amend the soil contents or mulch with organic compost.