How to Grow and Care for Sunflowers

Sunflowers (Helianthus annuus) are treasures of the summertime. These low-maintenance plants typically begin blooming in midsummer and can persist into early fall. The flowers, which stretch around three to six inches across on average, have a broad central disk surrounded by short, yellow petals.

These annuals are also available in other colors, like red, mahogany, cream, orange and bicolors. Sunflowers grow on a hairy, sturdy, upright stem that can reach up to 15 feet. Some varieties are fairly drought-tolerant.

Sunflower Care

• Sunflowers prefer a sunny location that gets at least six hours of sun per day and well-drained soil.
• They don't like to compete with weeds, so keep the garden clean.
• Mulching around your sunflowers will help maintain soil moisture and weed suppression.
• 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 about 1 foot tall.

Planting

Plant sunflowers after the last frost has passed, preferably once night temperatures have reach 50 degrees Fahrenheit. You can direct sow seeds into the ground about an inch deep. Maintain a few feet between each sunflower. Consider planting in a location where they will be sheltered from strong winds.

Light

For the best flowering and sturdiest stems, plant your sunflowers in full sun, meaning at least six hours of direct sunlight per day. Because they are heliotropic (their flower heads follow the sun), ample sun exposure will help sunflowers remain straight.

Soil

Sunflowers will grow in almost any soil, including poor, dry soil. However, they thrive in well-drained soil that contains a good amount of organic matter.

Water

Although tolerant of dry conditions, watering sunflowers regularly promotes blooming, as flowering often reduces 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 and Humidity

Optimal temperatures for growing sunflowers are between 70 and 78 degrees Fahrenheit. Still, they tolerate high heat as long as their moisture needs are met. Sunflowers can handle somewhat chilly but sunny environments.

They also tolerate high humidity but must have well-draining soil and good air circulation to prevent root rot and other diseases.

Fertilizer

Sunflowers appreciate a fertilizer high in phosphorus and potassium. If you have rich, loamy soil, you likely will not need to supplement it with fertilizer. If you have poor soil, apply a slow-release fertilizer starting in the spring.

Staking and Support

It can be helpful to plant sunflowers in groups to 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 become 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.

Types of Sunflowers

• H.annuus 'Russian Giant' can reach up to 12 feet tall and has a classic-looking flower.
• H. annuus 'Teddy Bear' reaches about 3 feet tall and has fluffy, double flowers that are beloved by bees and pollinators.
• H.annuus 'Giant Sungold' reaches about 6 feet tall and also has fluffy, double flowers.
• H.annuus 'Autumn Mix' blooms with a range of colors, including red and orange.
• H.annuus 'Italian White' has light yellow blooms that are nearly white with dark centers; it reaches about 7 feet tall.

Pruning

Typically, sunflowers don't require pruning but, if grown in clusters, can benefit from occasional trimming. You should cut annual sunflowers to the ground once they show signs of browning and drying. You can also deadhead them to try to get more blooms.

Propagating Sunflowers

Sunflowers can be propagated by taking cuttings and rooting them. The main benefit of propagating from cuttings is to create genetic uniformity in your garden. It's best to take cuttings before the season's growth has matured. Still, propagating these annuals with seeds is easier.

Here's how to propagate sunflowers from cuttings:

1. With pruning shears or a sharp knife, cut a 4- to 6-inch stem with no flowers or buds.
2. Remove the lowest leaves to expose nodes, and remove the top 1/2 inch of the cutting, leaving two terminal leaves behind.
3. Remove dust from the leafless section of the cutting and apply the rooting hormone.
4. Place the cutting in a sand and peat moss mix, ensuring that the leafless stem section is buried below the medium.
5. Keep the cutting in a warm place with light shade and cover it with a plastic bag.
6. Check the cuttings for roots after two to four weeks.
7. Relocate the cutting outdoors into light shade for a week before transporting it into full sun.

How to Grow Sunflowers From Seed

Sunflower seeds can be sown directly into the garden once the threat of frost has passed in the spring, or they can be started indoors three to four weeks before transplanting into the garden.

1. Plant seeds in the garden one to two inches deep in a shallow trench about 6 inches apart.
2. Keep them lightly moist (but not soggy) until they sprout, which takes around seven to 10 days.
3. Taller varieties should be thinned to about 1 to 1 1/2 feet apart; dwarf varieties can be grown about a foot apart.

Harvesting Seeds

To harvest seeds, cut the whole flower head with about 1 foot of stem attached, and hang it in a warm, dry, ventilated spot away from insects and rodents. Cover the seed heads with cheesecloth or a paper bag to catch loose seeds. When the seeds are completely dry, they can be easily rubbed off the flower head and collected.

Potting and Repotting Sunflowers

To pot a sunflower, select a pot suitable for its size. Fill the pot or container with loose potting mix and organic matter, and place it in direct sunlight. Generally, you may use a 7-gallon to 10-gallon pot or plastic container with good drainage. Since this is an annual plant, there is usually no need to repot it.

Overwintering

Annual sunflowers will succumb to frost so there's no need to overwinter the plant.

Common Pests & Diseases

Several pests and diseases can affect sunflowers. Birds and rodents are very fond of the seeds. So, if you'd like to save seeds for planting, cover the flower heads with netting to protect them from pests.

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.

You may have issues with beetles or caterpillars eating foliage. Sunflowers can be prone to fungal diseases, includingpowdery mildewand rust. To avoid such conditions, provide adequate air circulation around your plants and apply a preventive garden fungicide.

How to Get Sunflowers to Bloom

Sunflowers bloom with vibrant yellow petals and a sweet, woody scent in the summer. You can encourage blooming by giving your sunflower ample full sun and watering regularly. Handle the flowers very gently while they bloom.

Common Problems With Sunflowers

While sunflowers are a generally easygoing plant, they are still susceptible to some common issues.

Discoloration

Sunflowers can develop brown and black sores on their stems and leaves, often in humid months. This discoloration, called stem canker, can kill the plant quickly if unaddressed. Begin by applying a heavy-duty fungicide, but if the problem doesn't resolve, you should remove the sunflowers.

Leaf Spot

Sunflower leaves will sometimes display black or brown spots called leaf spot. Affected leaves will develop spots and then drop from the plant. You can try treating this disease with garlic spray or diluted apple cider vinegar, but if the treatments aren't successful, you will need to remove the leaves or the plant altogether.

From: thespruce