Saving cosmos seeds is an easy and economical way to preserve the seeds of this sweet romantic flower to plant in your flower garden the next growing season. Learn how to save cosmos seeds to continue to grow these cottage garden plants in your garden year after year.
Cosmos is an annual flower that gets planted in our garden every year.
It is a low-maintenance flower and makes a wonderful cut flower with a good vase life when picked in the right stage of growth.
Cosmos make a great addition to cut flower and cottage gardens.
The blooms are airy and ethereal, and always a pleasure to grow. The leaves are lacy and fine and soft to the touch.
For us it has many uses, as both a great flower and as well as a feathery filler.
I find myself growing more cosmos every year for this reason.
Saving Seeds Is Beneficial
Saving seeds helps to save on some costs for future crops, however it is much more than just that.
By saving the seeds of your plants you are actually saving the seeds of the most adapted plants in your garden, that have bloomed and then set seed.
These plants have grown in your own environment, and endured your weather patterns throughout the growing season.
If you harvest flower seeds and save your seed from year to year, over time the seeds will become more hardy and adapted to your garden space.
Cosmos seed is no exception.
We harvest and save cosmos seeds after every growing season, and plant them out again the following spring.
Cosmos are some of the easiest flowers from which to save seed.
Where Are The Seeds In Cosmos?
Cosmos seeds are located in the centre disc of the flower. Seeds will form on the flower if pollinators fertilize the tiny florets growing within the centre disc.
After blooming, the cosmos flowers will lose their colourful petals which surround the disc, as the seeds inside the disc begin to mature.
Cosmos tends to produces numerous flowers in different stages of growth, so you can often find mature seed pods on the same stem with fresh blooms.
I usually wait until the end of the season, and harvest at that time.
What Do Cosmos Seeds Look Like?
Cosmos seeds are light beige or brown in colour, and are elongated with a narrowing at each end.
The seeds measure approximately five to six mm in length.
The seeds are contained within the dried centre disc at maturity, along with white chaff and other plant debris. Mature seeds will fall easily out of the seed head at the slightest touch.
How To Save Cosmos Seeds
It is important to allow cosmos seeds to mature on the plant to get viable seeds for harvesting.
When the pod is mature, the seeds will just fall away from the pod with a simple touch.
For this reason , if you are planning to save the seeds for future planting, make sure to collect the seeds before they spill into the garden.
Generally there are always a few mature pods on each plant at the end of the season, even when some pods have lost their seeds.
Tools For Harvesting
- Container for collection, such as a seedling tray, a bowl, or a brown paper bag
- Pair of sharp scissors or snippers
- Labels to identify the seeds, such as a post it note to stick to the inside of the container, or a marker to write on the outside of the bag.
Harvesting Cosmos Seed
Harvest cosmos seed at the end of the growing season in early fall, when the seed heads have matured and you notice that the seeds become loose and begin to fall away from the pods.
Harvesting at this stage is ideal, and the seeds should be viable.
Chose a dry day on which to harvest so that the seed heads will be dry. This is important to help prevent moulding of the seeds.
Place your label inside or on your container. This is especially important if you are going to be harvesting more than one variety. It is very easy to mix seed heads up if they are not identified, as they often look similar.
For the collection you have several options:
- You can cut stems from the plant with multiple seed heads on each stem, or
- You can cut the individual seed heads and leave the stems in the field or garden.
I have done it both ways, depending on how many other flower seeds I also intend to harvest on that day.
Harvesting the stems with multiple seed pods is the fastest way, although you do have to separate the seed pods from the stem on the other end eventually when you bring them inside.
Removing The Seed From The Cosmos Seed Head
- Removing the seeds from the cosmos seed head is extremely easy, because the seeds are right there, mixed in with a bit of seed chaff.
- When the seeds are fully ripe, just brushing the seed pod with your finger will dislodge the seeds from the seed head.
- Hold each flower head over a container and give them a rub, allowing the contents to fall into your container.
Separating The Seeds from The Chaff
There is a bit of chaff with the cosmos seeds, although it is quite easy to distinguish the seed from the chaff. The seeds are easily picked out manually with a pair of tweezers.
It’s always a good idea to clean the seeds and remove as much chaff as possible before storing.
Drying Cosmos Seed
- To dry the cosmos seeds, spread them out on a surface so that they can air dry.
- I usually use a plate or a tray. A baking sheet is also an option if you have lots of seeds.
- Dry seeds for a couple of days before storing away.
Storing Cosmos Seed
Cosmos seeds can be stored in paper envelopes or Kraft bags, which will help to keep them dry.
Make sure to label your envelopes with the seed type and variety, along with the date, which should include the year as well.
For best results, store seeds in a cool dark place in a dry location.
The seeds will last for a few years or even longer given the right storage conditions.
How Long Can You Keep Cosmos Seeds?
Cosmos seeds will last from three to five years in storage if kept in ideal conditions.
Here is a great reference from Johnny’s seeds which includes a table with viability times for different seed types:
We usually don’t keep our seeds for this long, as we generally collect fresh seed every season, and plant out new plants the following year.
However, you may want to gift a few packages, or have some on hand for future years. It’s always nice to know that you can save your cosmos seeds for a few years, and that they will last for a while.
Will Cosmos Reseed Itself?
Cosmos does reseed, although not excessively in our zone 5b garden.
Whenever I find a volunteer cosmos plant, I am always happy to discover it. I generally let these self sown plants continue to grow wherever they have put down their roots if I possibly can.
Sometimes however the cosmos will pop up in spaces where the plant has to be moved, such as in a row where I have laid landscape fabric in which to plant another plant.
The tiny cosmos seedlings are easy to identify by their leaves, and occasionally will shoot up inside one of the holes in the fabric.
When this happens I will just dig them up and relocate them to another area in the garden.
Cosmos are great cut flowers, and they will always have a place in our cutting garden.
Saving cosmos seeds is a fun and easy activity for the end of the gardening season. It’s a great way to perpetuate these beautiful flowers in your garden year after year.
Seed saving is also economical, since the seeds saved are essentially free seeds straight from the garden.
Having the seeds from your own garden and the seed collection process is a wonderful experience. Keep in mind however that not all seed will come true to the parent plant.
If you have other cosmos varieties growing in your garden, the flowers will be open pollinated, and you may end up with different varieties of flowers, and even new hybrid plants.
Enjoy the fruits of your garden, save some cosmos seeds, and enjoy your sweet cosmos plants.
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Have you ever tried to save cosmos seeds from your garden? Be sure to leave a comment below to share your experience!