When to harvest sunflower seeds

Harvest sunflower seeds when the head droops to face the ground, the back of the head turns from green to lemon yellow or brown, and the small florets in the center have shriveled or fallen. Pull a few seeds to check that they are plump, hard, and black or black with white stripes. In most gardens that happens from late August to October. Cover the heads with a paper bag or cheesecloth once the petals brown, to keep birds off. Then cut the head with about a foot of stem and hang it upside down somewhere dry and airy.

Do not wait for the whole plant to die. Once most seeds have filled out and the back of the head is yellow, cut the head and finish drying it indoors, per Oregon State University Extension. That protects the crop from birds, squirrels, and fall rain that can cause mold. If you find many empty shells, the cause is poor pollination earlier in the season, per K-State Extension, not harvest timing.

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.

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.

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. Shells that stay flat and empty point to poor pollination, per K-State Extension.

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 check 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 keep critters from stealing your sunflower seeds before they are ready, protect the heads. K-State Extension recommends covering each head with a paper sack or cheesecloth once the petals begin to turn brown and securing it with a rubber band. This keeps birds out and catches any ripe seeds that drop. Avoid plastic bags, which trap moisture and cause mold.

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 by cutting each head with about a foot of stem attached, as Oregon State University Extension and K-State recommend. Hang the heads upside down in a dry spot with good air circulation, such as a garage or shed, and keep a cloth or paper bag tied around each head to catch falling seeds. Leave them to dry until the back of the head is brown and the seeds rub out with little effort.

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!

Seeds just removed from the head may still hold some moisture. If they feel at all damp, spread them in a single layer and let them dry for a couple of days before storing. Damp seeds can mold in storage.

Once dry, store the seeds raw or roasted in an airtight container in a cool, dry pantry. Oregon State University Extension notes that seeds turn rancid if kept at room temperature for long periods, so put them in the refrigerator or freezer if you want to keep them for months.

Sunflower seed harvest FAQ

How do you know when sunflower seeds are ready to harvest?

The head droops, the back turns lemon yellow to brown, the center florets shrivel, and the seeds are plump, hard, and black or striped.

What month do you harvest sunflower seeds?

Most gardens harvest from late August to October. K-State Extension expects harvest from mid-September into October in Kansas.

Can you harvest sunflower seeds too early?

Yes. Seeds that are white, soft, or flat will not fill out. Wait until most seeds have filled out, then cut the head and finish drying it indoors.

How do you keep birds off sunflower heads?

Cover the heads with a paper bag or cheesecloth once the petals begin to brown and secure it with a rubber band. Avoid plastic bags, which trap moisture.

How long do sunflower seeds last?

Dry seeds keep for a few months in an airtight container in a cool pantry. For longer storage, keep them in the refrigerator or freezer so they do not go rancid.

References

• K-State Research and Extension, Harvesting and roasting sunflower seeds
• Oregon State University Extension, Drying and roasting seeds (SP 50-534)