Updated date:

Sunflowers: Easy-to-Grow, Big Flowers With Large Seeds

I have "green-fingers," and love my garden. I enjoy watching wildlife and being outdoors.

Close-up of a large seed head from a sunflower (Helianthus annuus).

Close-up of a large seed head from a sunflower (Helianthus annuus).

Sunflowers (Helianthus Annuus)

Sunflowers brighten up your garden and attract birds and insects to your yard. The seed heads can also harvested for human food, producing both a tasty vegan snack food and delicious low-cholesterol sunflower seed oil. My favorite Helianthus variety is the Burpee Mammoth Sunflower as the seeds are lovely and large, making planting them easy. Make sure you buy fresh seeds that are intended for this year’s crop. There should be a plant-by or use-by date on the seed packet. If you have older seeds, they can still be planted, but their ability to germinate is reduced.

Large, Colorful, and Easy-to-Grow

Growing sunflowers (Helianthus annuus) is a good choice for beginner gardeners. The flowers are huge and the seeds are nice and big, making them easy to sow. The stem and leaves grow fast, so you will quickly see the result of your efforts. Sunflower plants need regular watering and plenty of sunshine. A sunflower’s daily growth spurt is noticeable, and it's fun to measure its increasing height every day. They are an annual plant and will flower (in the northern hemisphere) in August.

How to Plant, Grow and Harvest Sunflowers in Your Garden

How to Plant Sunflower Seeds

My favorite sunflowers are single stem, single large flower variety. I plant them towards the end of May directly in the ground where I want them to flower. I plant them at least 18 inches apart. This gives enough space for their large flower heads. They normally grow to a height of 6 to 8 feet. They grow best where they get a lot of sunshine, but not somewhere so hot that they get scorched.

If you intend to plant yours under glass in April, you can plant three seeds to each large plant pot. When the seedlings are 4 inches tall, you can prick them out into their final flowering positions outdoors. "Pricking out" means you remove them from the flowerpots and replant them in their final flowering positions 18 inches apart in your flowerbeds.

When to Plant Sunflower Seeds

The timing for outdoor planting depends upon where you live. For best results, daytime temperatures should be at least 60°F (16°C). You must also wait until the likelihood of overnight frost has disappeared. You can cheat nature a little by planting your sunflower seeds under glass. You can use either a green-house or a garden cold frame. Sheltering the ground like this warms it up and means you can plant a month ahead of normal.

With their large heads, sunflowers remind me of sunshine and blue skies.

With their large heads, sunflowers remind me of sunshine and blue skies.

Can You Grow Sunflowers From the Flower Heads?

Yes you can. You'll need to harvest the seeds when they are fully ripened in the flower heads. You'll be in competition with birds and other wildlife for these tasty morsels. I prefer to let the sunflower seeds get eaten by my feathered friends, so that they don't go hungry over winter. If you save the seeds to grow your own sunflowers, make sure they're completely dry before you store them. Otherwise they can become moldy and won't geminate.

Tallest Sunflower Competitions

Because sunflowers are so easy to grow, they are often used for competitions. The contests are fun to enter, and you’re likely to meet some friendly green-fingered people. Check out your local agricultural or village shows for tallest sunflower contests. The tallest sunflower was grown by Hans-Peter Schiffer in Karst, Nordrhein Westfalen, Germany in 2014, It measured 9.17 m (30 ft 1 in.)

If there isn’t already a competition nearby, why not start one yourself? Local schools and playgroups could get kids interested in the environment by running one. Growing sunflowers is a great activity for children. The large individual seeds are easy for small, clumsy fingers to hold. Once planted, sunflowers grow very quickly, so kids enjoy checking a plant’s growth spurt each day.

Can You Grow Giant Sunflowers in Pots?

Yes, you can grow any sized sunflower in a pot. However, the bigger the expected size of the plant, the larger the size of pot you'll need. For mammoth sunflower varieties, you should use at least a 5 gallon pot. Place the container in its final position before you fill it with soil. It will be too heavy to relocate once the plant has grown.

How and When to Harvest Sunflower Seeds to Plant for Next Year

RHS Recommended Plants For Kids

The Royal Horticultural Society (RHS) recommends sunflowers as an ideal plant for kids to grow and care for. They give the following tips.

  • When choosing a packet of sunflower seeds, remember to look to see how tall it might grow.
  • Sunflowers can be sown straight in to the ground where they are going to flower, so make sure the space you are going to sow is weed free.
  • Don’t forget to water the seeds. As they grow, if the plants are crowded, thin them out to about 45 cm apart, leaving the strongest, tallest plants.
  • Slugs and snails like to eat the new shoots. You may like to protect the plants by cutting the top off a plastic bottle and placing it over your seedlings.

Sunflowers Turn to Face the Sun

When I first started to grow sunflowers, I planted them next to a fence, thinking they would automatically face towards my house. This was true only for as long as the stems were short enough for the fence to block direct sunlight. Once the plants got to the top of my fence, however, their flower heads turned to face the sun, which in my case was away from my house. My lucky neighbor got all the benefit of my hard work. It was a tough lesson to learn. So, make sure you think about the direction of the sun and plan your planting accordingly if you want to avoid my mistake.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.