When to harvest sunflower seeds

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Sunflower seeds are commonly harvested in September when the petals have all fallen off, and the back of the flower head is turning yellow or brown.

When the seeds are ready, the sunflower heads droop, curl back on themselves, and the back of the heads turns a yellow-brown color (no longer green). The tiny petals on the central disk have fallen off the top of each seed (or are easily brushed off), showing the tops of large seeds.

Upon pulling out a few seeds, they should be plump and have hardened shells. They’ll also have matured from a white color to a black tone or black-and-white stripe pattern.

When you observe these signs, it’s time to snip off the sunflower heads, let them dry out in a sheltered location, and then collect the seeds from each head.

Sunflower seeds in head drying on stalk in field

When to harvest sunflower seeds

Sunflower seeds are ready to be harvested when they have grown to their expected mature dimensions and have developed their characteristic black or black-striped hull color. This generally corresponds to the plant’s leaves turning yellow, the back of the flower heads turning yellow-brown, and the tiny petals on the center disc of the flower head have fallen off.

September is the most common month for harvesting sunflower seeds. The seeds may be mature enough to harvest in warmer areas in August. Colder zones that have a late start in the spring may have to wait until October for the seeds to mature inside the flower head.

When and how to harvest sunflower seeds

Signs its time to harvest your sunflower heads

Here are the signs that indicate its time to cut the heads off the sunflowers:

  • The sunflower heads curl back on themselves and droop down toward the ground.
  • The back of the sunflower heads turns a yellow-brown color.
  • The leaves of the plant start to turn yellow.
  • The tiny petals on the central disk have fallen off the top of each seed.
  • The seeds are as large as the seeds planted in the first place.
  • The seeds have their characteristic ripe coloring (black or with black stripes).
  • The seeds have hardened hulls.

Reasons not to wait too long to harvest sunflower heads

While you do want to wait for the seeds to be fully formed before cutting the heads off the plants, there are a few reasons not to leave the sunflower heads standing too long:

  • Heavy fall rains can cause mold growth and rot, destroying the crop of sunflower seeds.
  • Hungry garden critters like birds and squirrels can get to your sunflower seeds before you do, potentially spoiling the harvest.

Checking the maturity of the seeds

Immature sunflower seeds tend to be white and have tiny little petals attached to their tops. The hull has not yet formed its hard shell around the seed and does not yet have its characteristic color. Immature seeds are also smaller than the seeds that were planted, as they are not yet fully formed.

When the seeds are ready to harvest, they will be plump and have hardened shells. The color of the hulls should also be a black tone or black-and-white striped.

To ensure your seeds are mature enough to harvest, it is best to pull out a few and look under the petals. If you press a finger into the hull and it dents easily, it is not yet mature. Wait until when it is hard to the touch before harvesting. You’ll also want to compare the seed to the seeds you planted or to an article about that specific variety. There is a huge variation in sizes between different types of sunflowers!

To prevent critters from stealing your sunflower seeds before they are ready to be harvested, make sure you protect them. As soon as the petals begin to wilt, quickly place each head in a brown paper bag, cover it with fine mesh or piece of cloth, and secure it at the base using a rubber band or twist tie. This will ensure that no seeds fall out or are nibbled on while they wait for maturity.

Harvesting sunflower seeds

Once you’re confident your seeds are ready for harvest, there’s no need to wait any longer – happy harvesting!

Start the harvest process by snipping the heads off the stalks about 4 inches below the flower head and hanging them upside down. Position them in a warm and dry area such as an attic, basement, or garage. Leave the flower heads to dry for two weeks or until the back of the head is completely brown, and you can easily rub off the seeds between two fingers.

Once dried, simply rub your hands over the surface of each sunflower head to remove the seeds. Put a tarp or sheet down below your hands to catch the seeds. You can also use wire mesh on top of a bucket. Be sure to check the area around you when harvesting, as some of the seeds may have fallen when snipping off the heads!

Sunflowers for birds
Get the seeds before the birds do!

Sunflower seeds are usually still a bit moist after the seeds have been taken off the heads. These seeds store best at a moisture content of about 10% and can spoil more quickly at higher moisture content. If the seeds feel at all moist, spread them out and let them dry for a couple of days.

After collecting and drying your sunflower seeds, it’s time to store them for future use. To ensure that your sunflower seeds are stored well and last a long time, be sure to keep them in an airtight container and store them in a cool, dry place. With proper storage, sunflower seeds can last up to one year when stored correctly.

Mary Jane Duford
Mary Jane Duford

Mary Jane Duford is a quintessential Canadian gardener. An engineer by trade, she tends to an ever-expanding collection of plants. In her world, laughter blooms as freely as her flowers, and every plant is raised with a dash of Canadian grit.

Mary Jane is a certified Master Gardener and also holds a Permaculture Design Certificate. She's also a proud mom of three, teaching her little sprouts the crucial difference between a garden friend and foe.

When she's not playing in the dirt, Mary Jane revels in her love for Taylor Swift, Gilmore Girls, ice hockey, and the surprisingly soothing sounds of bluegrass covers of classic hip-hop songs. She invites you to join her garden party, a place where you can share in the joy of growing and where every day is a new opportunity to find the perfect spot for yet another plant.

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