How to Grow Sunflowers from Seeds

Sunflowers are annual plants with large or small yellow flowers that bloom in the summer. They are loved for their beauty and are also easy to grow. Planting sunflower seeds in the spring is an enjoyable experience for both children and adults alike. You can grow sunflowers from seeds with just a little time and minimal preparation.

Check the outdoor temperature. While you can start sowing seeds indoors, sunflowers grow best when directly planted in the ground. Sunflower roots are very sensitive to movement, so the plant may die if transplanted. They thrive in temperatures between 18–33ºC, but you can plant them at slightly lower outdoor temperatures once the last frost has passed.

• Typically, sunflowers reach full growth and produce seeds within 80–120 days, depending on the variety. If your growing season is shorter, plant sunflowers at least 2 weeks before the last frost; most seeds should survive.

Select the right sunflower variety. There are many sunflower varieties and hybrids. Most gardeners will focus on a few key characteristics that are typically listed on the seed packet or online. Pay attention to the maximum height of the plant, as sunflowers come in dwarf varieties that grow under 30 cm and giant ones that can reach over 4.5 meters. Additionally, decide whether you want a sunflower with a single stem and one flower, or one that produces multiple stems with several smaller flowers.

• Roasted sunflower seeds cannot be planted, but you can sow seeds used for bird feed if they still have their outer shell.

Wrap the seeds in a damp paper towel. Moisten the paper towel, but avoid soaking it or letting water drip. Place the sunflower seeds on one half of the towel, then fold it to cover the seeds.

• If you have many seeds and don't mind a lower success rate, you can skip this step and sow the seeds directly into the ground. Seeds sown directly in the soil typically take about 11 days to sprout.
• If your growing season is longer, try sowing seeds in multiple batches, with two-week intervals between each, so you'll have a garden filled with flowers for a longer period of time.

Place the paper towel in a plastic bag. Put the damp towel into a plastic bag. Check it every day or two, and continue checking once the seeds begin to sprout. Typically, the seedlings will emerge within 48 hours. At this point, you can plant them in the ground.

• For the best results, keep the towel at a temperature above 10ºC.

Pinch the seed coat (if necessary). If the seeds haven't sprouted after two or three days, you can try pinching the edge of the seed coat with your fingernail. Be careful not to damage the seed inside. Add a few drops of water if the paper towel seems too dry.

Choose a sunny spot. Sunflowers thrive when they receive 6-8 hours of sunlight each day. Select a location that gets direct sunlight for most of the day.

• Unless your garden is regularly exposed to strong winds, plant sunflowers away from trees, walls, and other objects that may block sunlight.

Check for deep soil drainage. Sunflower roots grow deep into the soil and may rot if the ground is waterlogged. Dig a hole about 60 cm deep to check the firmness and compactness of the soil. If possible, add compost to improve drainage in the soil.

Consider soil quality. Sunflowers are not very picky and can grow in average garden soil without much adjustment. If the soil is nutrient-poor or if you want to encourage better growth, you can add rich, fertile compost to the planting area. pH adjustments are rarely needed, but if you have a pH testing kit, aim for a pH range of 6.0 to 7.2.

• Fertile soil is ideal for giant sunflower varieties, as they require more nutrients.

Sow sunflower seeds about 2.5 cm deep and 15 cm apart. Plant the seeds in holes or trenches 2.5 cm deep, or 5 cm deep if the soil is loose and sandy. Space the seeds at least 15 cm apart to allow room for growth. If you only have a few seeds and don't want to discard weak plants, space them about 30 cm or 45 cm apart for giant sunflower varieties. Cover the seeds with soil after sowing.

• If planting in bulk, sow the seeds in trenches spaced about 75 cm apart or at a distance that allows for the use of farm machinery.

Keep the soil moist around the seedlings. Maintain soil moisture without making it soggy until the seeds sprout and emerge from the ground. When the seedlings are small and delicate, water about 7.5-10 cm away from the plant to encourage root growth and avoid disturbing the young plant.

Protect the plants from pests. Birds, squirrels, and snails love sunflower seeds and may dig them up before they have a chance to sprout. Place a net over the soil to prevent this without hindering seedling growth. You can also place slug bait or use snail repellent around the plants to create a protective barrier.

• If deer are in your area, use wire mesh fencing around the plants when they start to leaf out. You can secure a 90 cm wire mesh around the plants with bamboo or wooden stakes about 1.8 meters tall to keep the deer away.

Water once a week for mature plants. Once the stalks have developed and the roots are established, reduce watering to once a week. Water deeply each week, and increase the amount when the weather is dry. Sunflowers require more water than most other annual flowers.

• The period before and after flowering is crucial, and lack of water can damage this process. Continue watering weekly as flower buds begin to form.

Thin out the plants (optional). When the plants are about 7.5 cm tall, remove the smaller and weaker plants so that the remaining ones are spaced at least 30 cm apart. This spacing allows the stronger plants to have more space and nutrients to grow taller and produce larger flowers.

• Skip this step if you want smaller flowers for bouquets or if you've already planted the correct spacing from the beginning.

Use little or no fertilizer. If you're growing sunflowers purely for enjoyment, avoid using fertilizer, as the plants can thrive without it, and too much fertilizer can harm them. If you want to grow taller sunflowers or plant many for harvesting, you can dilute fertilizer in water and apply it to the "watering trench" around the plants, away from the root. A balanced, nitrogen-rich fertilizer is usually the best choice.

• Alternatively, you can apply slow-release fertilizer once to the soil.

Install a support stake if needed. When the sunflower reaches over 90 cm or for varieties with multiple branches, you may need to use a stake for support. Tie the stem loosely to the stake using fabric or soft material.

Harvest sunflower seeds (optional). Sunflowers usually last for 30-45 days. Towards the end of this period, the green petals will begin to turn brown. If you want to harvest sunflower seeds for roasting or to save for planting next season, cover the flowers with paper bags to prevent birds from eating them. Harvest when the flowers are fully dry.

• If left on their own, sunflower seeds will naturally fall to the ground and grow the following season. However, harvesting helps protect the seeds from pests.

• Sunflowers release chemicals that can inhibit the growth of potatoes or beans, and they can even kill weeds if they grow naturally. However, these chemicals are harmless.
• Avoid planting sunflowers near brick structures, as their stems may grow between the bricks and potentially damage the building.