How to Grow Sunflowers
Bright yellow sunflowers are the poster flower of summer. They typically begin blooming in the mid-summer and can persist into early fall. The flowers, which stretch around 3 to 6 inches across on average, have a wide central disk surrounded by short petals. The main species plant features orange-yellow petals with a brown or purple disk, but growers now have produced flowers in several other colors. Sunflowers grow on a hairy, sturdy, upright stem that can be several feet high. The stems can hold a single flower or be branched with multiple flowers. Rough, hairy, oval to triangular leaves grow along the stem. In the fall, the disks give way to sunflower seeds, which are a major draw for birds and other wildlife.
Sunflowers get their common name because the flower heads turn toward the path of the sun each day. These flowers are annuals, meaning they complete their growth cycle in one year. Thus, they are fast-growing plants and typically will reach their flowering maturity around 80 to 120 days after the seeds germinate. They should be planted in the spring after the garden soil has warmed to at least 55 degrees Fahrenheit.
About the only mandatory requirements for growing sunflowers are a sunny location and well-drained soil. If possible, select a location that is sheltered from strong winds that might topple these towering plants. It can be helpful to plant sunflowers in groups, so they can support each other against wind and rain. Growers often have to stake their sunflowers, especially the tall varieties, to keep them growing upright. The plants can get very top-heavy when in bloom. Planting sunflowers along a fence is the easiest way to stake them. Bamboo stakes are also strong enough to keep them upright. Use care when inserting the stakes, so you don’t damage the plant’s roots.
Sunflowers don’t like to compete with weeds, so keep the garden clean. Mulching around your sunflowers will help with both maintaining soil moisture and weed suppression. Furthermore, wildlife is often attracted to sunflower seedlings. So it’s best to protect seedlings with row covers or screening, removing the cover once the plants are 1 to 2 feet tall.
For the best flowering and sturdiest stems, plant your sunflowers in full sun, meaning at least six hours of direct sunlight on most days. Because they are heliotropic (their flower heads follow the sun), ample sun exposure will help them remain straight rather than bending toward the direction where the light is predominant.
Sunflowers will grow in almost any soil. They can tolerate poor, dry soils. However, they will do best in well-drained soil that contains a good amount of organic matter.
Although tolerant of dry conditions, watering sunflowers regularly will help them set flowers. They often stop blooming during periods of drought. Allow the top 1 to 2 inches of soil to dry out between waterings. If your sunflowers are drooping and the soil is dry, that’s often a sign they need more water.
Temperature & Humidity
Optimal temperatures for growing sunflowers are between 70 and 78 degrees Fahrenheit. But they are tolerant to high heat as long as their moisture needs are met. And they can handle somewhat chilly but sunny environments. Plus, they’re tolerant to high humidity, but they must have well-draining soil and good air circulation to prevent root rot and other disease.
Sunflowers appreciate a fertilizer high in phosphorus and potassium to remind them that they’re supposed to set flowers on those tall stalks. If you have a rich, loamy soil, you might not need to supplement with fertilizer. But if you have poor soil, apply a slow-release fertilizer starting in the spring, following label instructions. Be careful not to overfeed your plants, which can cause the stalks to become spindly.
Common Pests & Diseases
Several pest and disease issues can affect sunflowers. Birds and rodents are very fond of the seeds. Moreover, the sunflower moth lays its eggs on the plant, and the larvae feed on the flower heads, tunneling and leaving holes in the seeds. Pesticides can help to control the moths. Similarly, you might have issues with beetles or caterpillars eating foliage. Sunflowers also can be prone to fungal diseases, including powdery mildew and rust. To avoid such diseases, provide adequate air circulation around your plants, and apply a garden fungicide as soon as you spot the first signs of infection.
Information Courtesy of TheSpruce.com