Every August, I always manage to come across at least one seed head that should’ve been collected 3 days ago.
It is usually something that is just very frustratingly obvious. The poppy capsule that was perfectly ripe last Monday is empty by Thursday, or the nigella pods that I “reserved for later” decided to burst after one windy day. And not to forget the coneflowers – I finally get to check them and realize that the goldfinches have done my work for me.
Well, it’s fair enough. After all, they were there first.
However, late summer is definitely one of the easiest times to store seeds for next year’s flower bed for free. But even if you’ve already bought a packet of ‘Apricotta’ cosmos, ‘Queen Lime Red’ zinnias, or beautiful cottage-garden nigella back in spring, saving some seeds instead of purchasing another packet next February is a much better idea.
Of course, the main question is when is the seed mature enough, since August of the calendar does not always mean August in your garden. A gardener in Minnesota could just begin collecting the first ripe seeds of cosmos at the same time when the spring poppies disappeared in inland California about 6 weeks ago. Foxglove capsules could still be ripening in a cool Zone 5 garden, while the plants growing in a hot Zone 8 garden already spread half of their seeds.
Therefore, I would certainly not go out into the garden in August and start harvesting simple because its “seed-saving season”. Instead, just listen to what the plant says. Usually, a flower or a pod starts drying and losing its green color, while the seeds inside become hard and full-sized and have proper colors. If you harvest seeds too early, you can store immature seeds that will not germinate; on the other hand, if you wait too long, the wind, birds or the plant itself will be able to take care of your job.
So if you’re wondering which flower seeds to collect in August and how to tell when they’re ready, these are the ones I’d start checking first.
1. Snapdragons
Usually by the end of August I stop removing the dead flowers from a few of my favorite snapdragon spikes and allow them to produce seeds. It seems somewhat wasteful after many weeks of careful deadheading, but after I stop pruning, I can observe the development of the seedpods on those same stalks.
The pods begin their life as green and juicy, and since the flowers open in succession from the bottom to the top of the spike, the capsules at the bottom become ripe before the ones at the top. That is why I start looking for ripe pods when the ones in the bottom part of the stalk turn brown, dry, and papery.
It is important to note that a ripe snapdragon pod becomes ready for harvest because it develops small openings at the top. Once this happens, it is possible to simply turn it upside down over an envelope and collect dozens of black seeds with ease. In case there are some lower pods ripe and some upper ones are still developing, I harvest the whole spike to allow it to dry indoors.
In this way, it is possible to protect myself from accidentally losing ripe seeds while waiting for the others to ripen. The pods do not have to be collected all at once; one or two of the most productive spikes will provide enough pods to save from. And in case if your snapdragons continue to bloom, it means they still need to produce more flowers.
2. Black-Eyed Susans
Usually, by August, Rudbeckias have two processes going on simultaneously. Fresh flowers continue attracting bees, and the first blooms turn into dark bristle-like cones.
These cones contain seeds, but don’t be in a hurry to harvest them yet. When harvesting black-eyed susan (Rudbeckia hirta), I wait until the flower head dries out completely, and the stem right below begins to brown. While one may think that the cone is ready to be harvested, since it has just lost all its petals, the seeds are not developed yet.
After you harvest them, leave a couple of flower heads to dry up in the paper bag during another several days. Afterwards, rub the cones in your hands above a tray. Seeds should come out very small and dark; there will also be lots of chaff – which is completely natural. Just remove large pieces of chaff and don’t be concerned about cleaning the seed.
If plants have already bloomed, then you may harvest ripe flower heads in August, otherwise it may take several more weeks. Moreover, I never harvest all the flower heads but leave some of them in order to attract goldfinches and other little birds.
3. Columbine
Columbine is an easy one to save, but timing can be tricky because those pods do not stand around awaiting your arrival once they are ripe. After the Aquilegia blooms fall off, several long, thin green pods form in their place, and after the following weeks, these pods gradually turn from green to brown.
As soon as the pods start splitting open at the tips, I know that the dark hard seeds inside are mature enough to fall off. By the time all the pods become fully opened, all it takes is a gust of wind or even brushing by a plant when watering, to lose a lot of seeds in the mulch.
Thus, instead of cutting off the stalk beforehand, I simply hold a paper envelope under the pod and gently shake it out. As soon as the seed is ripe, it pops out easily; in case you need to break a stubborn green pod, just give it some more time.
August is a good time for harvesting in cooler climates, whereas plants growing in milder ones may be already done earlier. In addition, if there are several columbines planted in the same place, do not expect all of them to look exactly like their mother, since they easily crossbreed. However, it is just one of the reasons I find their random colors so charming for self-sowing plants.
4. Zinnias
By the time August arrives, I begin to purposely ruin some of the nicely looking zinnias.
After several weeks of deadheading, it is rather unpleasant to do it, but if you intend to gather seeds from Zinnia elegans, there is no other way – the gardeners say that you need to let some flowers complete the senescence process which means to let them become thoroughly brown and crispy. So I choose flower heads from those plants that were flowering abundantly, looked good and did not suffer from powdery mildew infection because the flower color is not the only characteristic to inherit.
And then I wait longer than I want to. It is true that the faded bloom does not mean that the flower head is already ripe; therefore, I have to see brown and papery petals, crispy center and dried stem right beneath the flower. Having pulled the ripe flower head, I will see the seeds inside along with the dried petals. However, not all of them look the same because the seeds develop in various parts of the flower; some of them are rather wide and arrow-shaped and the other ones are narrower.
I select only those that seem firm and well-filled and reject those that are fragile, white or apparently empty. If it rains in August, I will not insist on keeping the nearly ripe flower head outside because a week of rain can make it mold in the flower head.
5. Coneflowers
I know my coneflower seed is ripe when the goldfinches decide the border belongs to them.
And, evolutionarily, they’re right. The purple coneflower (Echinacea purpurea) was designed to carry those mature seeds through the summer months within their tough cones, and therefore by late summer a single plant can have flowers to feed the bees, cones to harvest for myself, and another full menu for the birds.
I begin harvesting the earliest cones but wait until not only the petals have dropped off but the cone is hard and dry, and ideally have seen a browning on the stem above the cone. That way I know it’s been able to fully mature its seed. Cutting them too early means lots of dried cone material but not much viable seed.
After collecting a few of the cones from the garden, I let them dry indoors for a few additional days before separating them over a flat surface. Wear gloves if your fingers are sensitive – dried echinacea cones are reminiscent of miniature porcupines. The result will be viable seed combined with a good bit of chaff, so I sort the firmer, heavier pieces, not trying to preserve everything that falls out.
And “a few” is a relative number. A couple of cones are enough to produce a great deal of seed, while the remainder provide food for goldfinches through the autumn months and added interest once the rest of the border is flattened by frost.
That’s why the birds get their fill, too. They generally win out anyway.
6. Foxglove
The maturing of foxglove seed occurs gradually, which is why I never wait for the whole flower stalk to turn brown before harvesting. As mentioned above, common foxglove (Digitalis purpurea) blooms from bottom upwards, and the pods mature in the same sequence, so by August you may already find dried brown pods on the base of the stalk and totally green pods on its top.
Once the lower pods become papery and start cracking, the seed inside is ready. Since foxglove seed is extremely small and lightweight, I prefer to cut off the upper stalk with the pods and put it directly into a paper bag. Then it will dry out a little more in a warm dry place for several days.
After that, you only need to give the bag a few shakes, and hundreds of tiny seeds will gather at the bottom. It is much more convenient than trying to catch individual seeds on a windy day.
Usually, August is a good harvesting time in cooler climates, whereas foxgloves in milder ones ripen earlier. In addition, common foxglove is a biennial plant, and therefore, the seeds you plant grow leaves first and bloom in the following year.
By the way, remember about the dangerous of foxglove; it is poisonous if eaten, including the seed.
7. Poppies
Poppies are among those flowers where collecting the seeds seems so easy, although sometimes they can teach a lesson for those who are a bit late. As soon as annual poppies, for example, Papaver somniferum, drop their petals, the round green capsule left on the stalk gradually dries out and hardens turning into pale brown and woody.
During the process of ripening some cracks appear under the flat lid on the top side of the pod, meaning that the pod turned into a little shaker. Any light movement of the pod will give you the indication of ripeness of the seeds – the sound of a dry rattle.
That is the moment when I start collecting.
No need to open the capsule, just turn it over the paper bag or bowl and tap the stem a couple of times. Seeds come out from these cracks very easily, while the pod itself can remain upright if you like the appearance of dried pods in your garden.
The only difficulty is that wind can shake the seeds in the same way as you do, and so if the capsule is dry and rattle I do not wait any additional week “to be sure.” In a warm garden, poppies can be ready by August since they are not fond of hot days, and in northern gardens late planted poppies can still be ripening.
8. Nigella / Love-in-a-Mist
The love-in-a-mist (Nigella damascena) literally lets you know when it is time to collect the seed. Following the flower blooming, the plant produces inflated, striped, balloon-like seedpods that can be found between the leaves.
Initially, the seed pods remain green and juicy but eventually turn brownish and begin rattling with the movement. I wait for this sign to harvest a complete pod and put it in a paper bag right before the plant starts spreading its own seeds.
After a few more days of drying indoors, I tear the seed pods apart by hand. The papery capsules yield an abundance of small black seeds and I merely need to remove the pieces of plant material from the mixture.
In hotter climates, nigella might be ready for harvesting much sooner than in colder regions where the ripening seed pods can remain on plants until August. In case some pods escape your attention, do not get upset since nigella will grow from the seeds sown by itself.
9. Cosmos
Cosmos is never waiting until the whole plant is finished blooming before she starts letting her seeds drop, which is why I often harvest her when I’m busy with something entirely different.
I’ll be walking past Cosmos bipinnatus with the watering can, brush one dried head with my fingers, and find myself holding a little handful of those long, black seeds.
This is basically what the ready test is.
After the petals drop, seeds will form in the loosely arranged “starburst,” starting out pale and fluffy. As they ripen, they will elongate, becoming dark brown or even nearly black and stiff. If they can easily pull away from the flower, I’ll put an envelope nearby because even a windy August afternoon can blow the whole works away in a surprising hurry.
What I like about cosmos is that one plant may do everything all at once – buds on top, fresh blossoms with bees in them, faded blossoms underneath, and finally ripe seeds. So there’s no need to “finish” the plant to begin harvesting; you just go through it picking the seeds from the heads as they ripen.
If more than one color is growing in the garden, be prepared to see the colors mix some next year, as cosmos will cross.
10. Calendula
Calendula seeds appear as if the gardener simply swept up the potting bench at harvest time.
The first time you dissect the flowerhead of Calendula officinalis, you will encounter curled seeds, large seeds, hooks, and many other different forms that seem not to have anything in common with each other. However, that is all right and, after a while of practice, it turns out that the calendula seeds are among the easiest to gather.
I leave the flowerhead undisturbed until the unusual seeds turn from green and flexible to tanned or brown and firm and then rub the flower over my hand. When everything starts to come off without much effort, I start gathering and when I am still fighting green parts, I know that I am too early.
Since calendula likes the cool season, you can find the seeds together with fresh flowers in August, and I quite like that since you can gather from the mature flowerheads and keep deadheading the rest to encourage flowering instead of telling the plant that the summer is already gone.
A couple of flowerheads provide enough.
11. Sweet Peas
Collecting sweet pea seeds requires that you break one rule: Stop deadheading one or two stems of Lathyrus odoratus early. Deadheading all of the spent blooms will prevent your sweet pea plant from forming its characteristic pea pod.
The pods are initially green and fleshy, but despite being tempting for collection at this point, they require a bit of patience as the seeds inside are not ripe yet. The mature pod turns from green to light brown and becomes somewhat brittle to touch as it dries out. You might even notice some twisting of the pod, indicating that it is ready to burst open, which is the perfect time to harvest it.
I then shell the pod just like the regular garden pea and air-dry the seeds somewhere else for a few days. I don’t need a lot of pods to save, so I select plants with the best flowering and the most vigorous growth for seed collection.
If your sweet pea continues flowering into August, do not rush them. Your garden is cooler and could provide more time for the flowering, while the hot summer will force the plants in warm climates to go dormant earlier. Remember only one thing when labeling your envelope: Ornamental sweet pea seeds are not edible.
Written By
Amber Noyes
Amber Noyes was born and raised in a suburban California town, San Mateo. She holds a master’s degree in horticulture from the University of California as well as a BS in Biology from the University of San Francisco. With experience working on an organic farm, water conservation research, farmers’ markets, and plant nursery, she understands what makes plants thrive and how we can better understand the connection between microclimate and plant health. When she’s not on the land, Amber loves informing people of new ideas/things related to gardening, especially organic gardening, houseplants, and growing plants in a small space.