September isn't just about preparing the garden for fall. It's also one of the best opportunities to collect and save flower seeds for next year's growing season.
As summer flowers finish blooming, their spent flowers begin developing mature seedheads. If you harvest them at the right moment, you can collect free seeds, preserve favorite varieties, and grow more flowers next year without buying another packet.
But timing is everything.
Collect seeds too early and they may be immature. Wait too long and the seedheads may split open, scatter their contents, or become damaged by birds, rain, or wind.
The good news is that many popular garden flowers are producing collectible seeds right now.
Here are 10 flower seeds you may still be able to collect in September, plus simple tips for harvesting, drying, storing, and planting them.
Why Collect Flower Seeds in September?
September sits at an interesting point in the gardening calendar.
Many summer flowers have finished their peak display, but their seedheads are now reaching maturity.
That makes the month ideal for checking plants throughout the garden.
Saving your own seeds can:
- Reduce gardening costs
- Preserve favorite flowers
- Give you a supply for next spring
- Help you grow larger displays
- Encourage a more self-sufficient garden
- Allow you to select seeds from your healthiest plants
There's also something satisfying about watching a plant produce the material needed to create next year's generation.
However, remember that seeds collected from hybrids may not produce plants identical to the parent plant. Open-pollinated varieties are generally more predictable for seed saving.
1. Marigolds
Marigolds are among the easiest flowers for beginners to collect seeds from.
As the flowers fade, the petals dry and the seedheads become brown and papery.
Inside are long, slender seeds that can usually be removed by hand.
How to collect marigold seeds
Wait until the flowerhead is completely dry.
Remove the dried head and gently pull it apart to release the seeds.
Choose seeds from healthy, vigorous plants that displayed the flower color and form you want to reproduce.
Store them in a cool, dry location.
September tip: Don't harvest green or soft seedheads. Give them more time to dry on the plant whenever weather conditions allow.
2. Zinnias
Zinnias can produce a generous supply of seeds after flowering.
Allow selected flowers to remain on the plant instead of deadheading them.
As the flowerheads dry, the seeds mature.
How to collect zinnia seeds
Wait for the flowerhead to become dry and brown.
Remove the entire head and gently separate the dried plant material.
Zinnia seeds are relatively easy to recognize because they're flat and elongated.
Choose seeds from healthy plants with desirable flowers.
One important consideration: if you grew several zinnia varieties close together, cross-pollination may mean next year's plants don't look exactly like the parent.
3. Sunflowers
September is prime seed-collecting season for many sunflowers.
Large flowerheads can contain hundreds—or even thousands—of seeds.
If you're saving sunflower seed for planting rather than eating, allow the flowerhead to mature and dry.
How to collect sunflower seeds
Watch for the back of the flowerhead to turn from green toward yellow or brown.
The seeds should look fully developed.
Cut the head and allow it to finish drying in a protected, well-ventilated location if necessary.
If birds are getting to the seeds before you can harvest them, a breathable protective covering can help.
Avoid sealing damp sunflower heads inside airtight containers.
4. Cosmos
Cosmos are excellent candidates for seed saving.
Their slender, dark seeds are easy to collect once the flowers have finished blooming.
How to collect cosmos seeds
Leave several flowerheads on the plant.
Wait until they turn brown and dry.
Cut the seedheads and gently shake them over a container or paper.
Remove large pieces of dried plant material.
Cosmos can readily self-sow in some gardens, so if you don't collect all the seeds, you may find volunteer seedlings appearing the following season.
5. Black-Eyed Susans
Black-eyed Susans (Rudbeckia) produce distinctive seedheads after flowering.
The central cone gradually dries and darkens, eventually containing mature seeds.
How to collect them
Allow the seedhead to dry thoroughly on the plant.
Cut the entire head and place it in a paper bag or container.
Once fully dry, shake or crumble the seedhead gently to release the seeds.
Don't expect every seed to germinate.
Natural seed production is variable, so collecting a reasonable quantity improves your chances of getting plenty of seedlings.
6. Coneflowers
Purple coneflowers (Echinacea) are another excellent seed-saving candidate.
Their dried flowerheads can remain attractive well into autumn, making them useful for both wildlife and seed collection.
How to collect coneflower seeds
Leave mature flowerheads on healthy plants.
Once the seedhead is dry, remove it and separate the seeds from the dried material.
You can store the seeds for later sowing or allow some to remain outdoors for natural reseeding.
If birds visit your coneflowers, consider leaving some seedheads standing for them while harvesting only a portion for your own collection.
7. Nasturtiums
Nasturtium seeds are unusually easy to spot because they become relatively large compared with many other flower seeds.
After flowering, green seed pods form.
As they mature, they become larger and eventually dry.
When to collect them
For seed saving, allow the seeds to mature fully.
They may fall naturally from the plant once ripe, so check beneath the foliage regularly.
Collect mature seeds and allow them to dry further in a well-ventilated location before storage.
Nasturtium seeds can be surprisingly useful for gardeners who want an inexpensive supply of next year's plants.
8. Calendula
Calendula is another flower that can produce plenty of collectible seed.
The curved, unusual-looking seeds develop inside dried flowerheads after the petals fade.
How to collect calendula seeds
Allow the flowerhead to dry on the plant.
Once the seeds have turned mature and dry, remove the head.
Separate the seeds from the dried flower material.
Calendula can also self-sow readily under favorable conditions, so don't be surprised if volunteers appear around the original plants.
9. Sweet Peas
Sweet pea seed can be collected after the flowers finish and pods develop.
The pods gradually become larger and dry as the seeds mature.
How to collect sweet pea seeds
Leave selected pods on the plant rather than removing them.
Wait until the pods have turned dry and brown.
Harvest before the pods split open and release their seeds.
Spread the seeds in a dry place for additional drying before storing.
Important: Sweet pea plants and seeds are not the same as edible garden peas, and sweet peas are toxic if eaten. Keep saved seed clearly labeled and away from children and pets.
10. Morning Glories
Morning glories produce distinctive round seed pods after flowering.
As the pods dry, they become ready for collection.
How to collect morning glory seeds
Allow the pods to dry naturally on the vine.
Collect them before they open and scatter their contents.
Break open the dry pods and remove the mature seeds.
Store them in a labeled, dry container.
Because morning glories can spread aggressively in some regions, check local recommendations before growing or intentionally distributing their seed.
How to Tell When Flower Seeds Are Ready to Harvest
The biggest seed-saving mistake is harvesting too early.
Look for several signs of maturity:
- Seedpods have changed from green to brown or tan
- Seedheads feel dry rather than soft
- Seeds are firm rather than milky or immature
- Pods may begin splitting naturally
- The plant has clearly finished flowering
The exact appearance varies dramatically between species.
Dryness is one of the most useful clues.
If the seedhead still feels moist, give it more time whenever possible.
The Best Time of Day to Collect Seeds
Dry weather is ideal.
If possible, collect seeds after morning moisture has evaporated and before rain or heavy evening humidity returns.
Avoid harvesting immediately after rainfall.
Moisture trapped inside seedheads can increase the risk of mold during storage.
If your region has frequent autumn rain, harvest mature seedheads during the first reliable dry period rather than waiting indefinitely.
How to Dry Flower Seeds Before Storage
Proper drying is one of the most important steps in successful seed saving.
Spread seeds or seedheads in a single layer on paper, trays, or another breathable surface.
Keep them somewhere:
- Dry
- Cool
- Well ventilated
- Out of direct sunlight
Allow them to dry thoroughly before placing them in sealed containers.
Don't use high heat to speed up the process.
Excessive heat can damage seed viability.
How to Store Flower Seeds
Once completely dry, place seeds in airtight containers or paper envelopes, depending on the type and your storage conditions.
Label every packet with:
Plant name + variety + collection year
You may also want to record the garden location or parent plant.
Store seeds somewhere cool, dark, and dry.
A stable environment is better than a location that repeatedly becomes hot and humid.
For longer-term storage, gardeners often use carefully controlled cool conditions, but seeds must be thoroughly dry before being sealed to prevent condensation and mold.
Can You Save Seeds From Hybrid Flowers?
Yes, you can collect seeds from hybrid plants.
But there's an important distinction.
The resulting plants may not resemble the parent.
Hybrids are produced by crossing selected parent plants, so their offspring can show different characteristics.
If you want predictable results, prioritize seeds from open-pollinated varieties.
Heirloom varieties are often particularly attractive for seed-saving gardeners.
Which Flowers Should You Not Save Seeds From?
Not every flower is equally worthwhile for seed saving.
Some ornamental plants produce sterile seeds, difficult-to-harvest seed, or offspring that vary substantially from the parent.
Some cultivars are also propagated vegetatively rather than by seed.
Before collecting large quantities, check whether the specific variety is known to come true from seed.
And if you're growing a patented or protected cultivar, check applicable propagation restrictions before intentionally propagating it.
Don't Forget to Leave Some Seedheads for Wildlife
Seed saving doesn't mean harvesting everything.
Many birds depend on mature flower seeds during autumn and winter.
Coneflowers, sunflowers, black-eyed Susans, and other plants can provide valuable food.
A simple compromise is to harvest a portion of your mature seedheads and leave the rest standing.
You'll get seeds for next year while still providing natural food and winter structure.
Common Seed-Saving Mistakes
Harvesting too early
Immature seeds may have poor viability.
Storing seeds while damp
This is a recipe for mold.
Forgetting labels
A mystery envelope of brown seeds is much less useful six months later.
Storing seeds somewhere hot
Heat can dramatically shorten seed longevity.
Collecting from unhealthy plants
Choose seeds from vigorous, disease-free plants whenever possible.
Expecting hybrids to reproduce exactly
Hybrid offspring may vary significantly.
How Long Do Saved Flower Seeds Last?
There's no single expiration date for seeds.
Longevity depends on the species, initial seed quality, moisture content, storage temperature, and storage conditions.
Some flower seeds remain viable for several years under good storage conditions, while others decline more quickly.
That's why cool, dry, dark storage matters so much.
If you're uncertain about viability, perform a simple germination test before planting large areas in spring.
Place a known number of seeds between moist paper towels or in another suitable germination setup and track how many successfully sprout.
Frequently Asked Questions
What flower seeds can I collect in September?
Good candidates can include marigolds, zinnias, sunflowers, cosmos, black-eyed Susans, coneflowers, nasturtiums, calendula, sweet peas, and morning glories, depending on your climate and when each plant finishes producing mature seed.
How do I know when flower seeds are ready to collect?
Most seeds are ready when their pods or seedheads have become dry and changed color from green to brown, tan, or another mature shade. Seeds should generally feel firm and dry.
Can I collect seeds from cut flowers?
Sometimes. The flower must have been successfully pollinated and allowed to mature seeds. Flowers harvested before seed development generally won't produce viable seed.
Should I dry flower seeds before storing them?
Yes. Seeds should be thoroughly dry before long-term storage. Store them only after excess moisture has evaporated.
What is the best container for storing flower seeds?
Paper envelopes are useful for short- to medium-term storage in a dry environment, while airtight containers can provide better moisture protection when seeds are completely dry. Always label the container.
Can I collect seeds from hybrid flowers?
Yes, but offspring from hybrid plants may not reproduce the parent plant's exact characteristics. Open-pollinated varieties are generally better choices for predictable seed saving.
Can I collect seeds after the first frost?
Sometimes. A light frost doesn't automatically make mature seeds unusable, but wet weather, repeated freezing and thawing, and seed dispersal can make collection more difficult. Collect mature, dry seedheads whenever practical.
Should I leave some flower seeds for birds?
Yes. Leaving some mature seedheads standing can provide food for birds and winter habitat for insects. Harvest only a portion if you want to support wildlife while saving seeds.
Can I plant saved flower seeds next spring?
Yes, provided the seeds are mature, viable, and properly stored. Label them with the plant name and collection year so you know what you're planting.
Final Thoughts
September is a perfect reminder that the garden isn't finished just because summer flowers are fading.
Those brown seedheads and drying pods may actually contain next year's garden waiting to happen.
From easy-to-save marigolds and zinnias to sunflowers, cosmos, coneflowers, calendula, and nasturtiums, many flowers can provide an abundance of seed at the end of the growing season.
The formula is simple:
Harvest mature seeds → dry them thoroughly → label them → store them cool and dry → test them before spring planting.
Don't feel like you need to collect everything.
Choose your healthiest plants, save seeds from the flowers you love most, and leave some seedheads behind for birds and beneficial wildlife.
A few minutes of seed collecting this September could save money—and give you a whole new generation of flowers next year.
