- Managing Nasturtiums: Controlling Spread and Maximizing Benefits - September 23, 2023
- How To Know if Nasturtium Seeds Are Viable - September 23, 2023
- Will a Mandevilla Come Back After a Freeze? - September 22, 2023
Nasturtium is a family of annual and perennial plants that are easily propagated via cutting or seed. Seed is the most common propagation method because the seeds are large and plentiful. As such, you may be wondering how to tell if the nasturtium seeds you collected are still viable.
The best way to know if nasturtium seeds are viable is to do a water test. Soak the seeds in room-temperature water for 15 minutes. The seeds that float are unlikely to germinate and can be thrown out, while the ones that sink are likely to grow and should be planted.
In this article, I’ll share tried-and-true ways to test nasturtium seeds for viability, and while neither method is better than the other, the time of year and planting conditions may dictate which method you choose. I’ll also give you some tips on how to collect and store nasturtium seeds for future success.
1. Do the Water Test
One very effective way to determine if nasturtium seeds are viable is to check them using the water test. This test is used by gardeners around the world to test the viability of any type of seed, not just nasturtium (source).
The water test is simple. Here’s how to do it:
- Fill a large clear dish with room-temperature water.
- Place the seeds you wish to test in the water and wait 15 minutes.
- After 15 minutes, look out for any seeds that are floating on the surface. These seeds can be discarded as they are most likely not viable.
- Retain the seeds that are sitting on the bottom of the dish. These seeds are viable and are more likely to germinate.
If it is time to plant the seeds, you can plant them from their wet state directly in the soil. If it is not planting season, pour as much water as you safely can from the dish. Remove the remaining seeds and place them on a large plate to air dry.
Once the seeds have dried thoroughly, which typically will take 24-48 hours, they may be safely stored again for planting.
2. Do the Germination Test
The other way to test your nasturtium seeds for viability is the germination test. This method involves creating conditions that will cause the seeds to germinate if they are viable. Here’s how to do it:
- Take a paper towel and dampen it slightly with room-temperature water. Lay it out flat and sprinkle water on it so you don’t have to unfold or unwrinkle it in the next step.
- Line up the seeds you want to test on the paper towel towards the center. Take care not to crowd the seeds together too closely.
- Fold the towel to cover the seeds with damp paper.
- Place the folded damp paper towel inside a ziplock bag and seal it.
- Place the bag in a warm spot, ideally with a bit of natural or artificial light to encourage growth.
- Check the bag every few days — but certainly after one week — to see if any of the seeds have sprouted.
Nasturtium seeds typically take 10-12 days to germinate (source). Be sure to check the seeds after 10-12 days have passed.
Viable seeds will have sprouted, whereas seeds that are no longer viable will likely not have changed in any way. From here, the germinated seeds can be planted directly into the soil to continue growing.
Note that since the germination test leads to planting the seeds, it is best to only perform this test at the start of the growing season or when you are ready to start your plant for the year.
How To Collect Nasturtium Seeds for Future Success
Successful seed harvesting from nasturtium hinges around knowing when to collect the seeds. Nasturtium seeds are larger and more visible than many other plants’ seeds, so it’s easy to start collecting and harvesting them too early in the season.
When harvesting nasturtium seeds, it is crucial to wait to gather them when the plant starts to wind down for the growing season in late summer or early fall. The flowers should begin to wither and close up, and you should see the vine showing no new signs of growth.
Harvesting the seeds too early will likely lead to seeds that will not germinate. Some gardeners may wait until the seeds fall off the vine, but waiting this long also increases the risk of collecting seeds that are no longer viable.
Instead, wait until the plant has shown signs of starting to prepare for dormancy, but before the seeds start to dry up and fall off the vine.
Ripe nasturtium seeds will be tan in color. You can gently twist them off the plant and collect any that have fallen to the ground.
For seed collection, I use seed starter trays because they are large and can catch seeds from the length of the vine all at once. My favorite seed starter trays are the SOLIGT Seed Starter Trays (link to Amazon) which come as a pack of three, each with its own individual lid.
Storing Nasturtium Seeds for Future Success
Harvested nasturtium seeds must be dried completely before they can be stored. This is another good reason to use seed starter trays when harvesting seeds.
The seeds can simply be left in the seed tray until they dry. Every day, shake the tray to move the seeds around to be sure all sides of each seed are drying evenly.
Seeds can take a few days up to several weeks to dry fully. Be certain that your seeds have fully dried before you store them.
The best storage vessels for dried seeds are glass jars or paper envelopes. Plastic is a poor alternative because it can cause the seeds to mold, rendering them useless.
My favorite seed envelopes are the Geyee Seed Saving Envelopes (link to Amazon). These envelopes come printed with space for you to jot down reminders of crucial information for all your collected seeds, like the seed type and collection date.
Seeds in packets or glass jars should be stored in a cool, dry location away from sunlight. A shelf in a closet or pantry is a great location for seed storage. ‘
Here is a really great video on germinating and growing your Nasturtium seeds:
Checking seed viability is a relatively simple task. In addition, it is equally important to harvest and store seeds properly in order to set them up for the greatest success in the future growing season.