Nasturtiums won’t germinate easily as the seed coating is dry, hard, and impermeable to water. You can create a nick on the seed using a metal file to let water into the seed. Soak such nicked seeds overnight in warm tap water and sow them immediately after 8 hours to germinate the seeds properly.
Nasturtiums are grown by many for their beautiful flowers. This beautiful plant can be grown both indoors and outdoors.
People often find it hard to get their Nasturtium seeds to germinate. Many have mailed me in the past few weeks regarding this.
There are a number of reasons why Nasturtium seeds won’t germinate. In this article, we shall explore the reasons and we’ll also discuss how to germinate Nasturtium seeds properly.
Do Nasturtium seeds need scarification?
Yes, Nasturtium seeds need scarification to germinate properly. The seed coat is hard and impermeable to water.
Experts from the University of Washington Botanic Gardens recommend scarification to let the seeds germinate optimally.
Make a small cut in the seed coat using the tip of a small knife. If you want to do it gently, scrape a side of the seed using a metal file until the inner part of the seed is seen.
Be careful while you do this, you don’t want to damage the seed. Soak these seeds in water before you sow them. Let’s look at the exact process.
Do you have to soak Nasturtium seeds?
Yes, soak Nasturtium seeds in a bowl of warm tap water overnight. Don’t soak the seeds for more than 8 hours.
The seeds get rotten if you soak them for more than 8 hours. Soak them only prior to planting them in the soil.
The nicked seeds absorb ample water through the scar and swell up to twice the size. This water in the seed helps it germinate.
Should Nasturtium seeds float?
No, Nasturtium seeds need not float on water. Push the floating seeds down into the water.
Let the seeds soak in water for 15 minutes before you observe them. Throw all the seeds that float. You can do this while you soak them in warm water.
Should Nasturtium seeds be started indoors?
Yes, you can start Nasturtium seeds indoors but it doesn’t mean that the seeds only germinate indoors. Use standard sterile potting mix.
Nasturtium seeds have a hard, impermeable outer layer. So, you need to follow the below guidelines to germinate the seeds properly.
How do you germinate Nasturtium seeds indoors?
- You can use individual 3-inch diameter seedling pots. One can also use a larger seedling tray.
- Make sure the pot/seedling tray has drainage holes.
- Plant the seeds 0.5 to 1-inch deep in the soil.
- Plant the seeds 2-inches apart from each other, if planting in a tray.
- If planting in a pot, add a single seed to each pot.
- The ideal germination conditions are 70F and even moisture in the soil.
Do Nasturtium seeds need light to germinate?
No, Nasturtium seeds don’t need light to germinate. You need to cover the seeds as they need darkness to germinate.
They do need sunlight after they germinate but not prior to this.
Nasturtium germination temperature
The optimal temperature range for Nasturtium seed germination is 55-65F. At this temperature, the seeds take a week or two to germinate.
Place the seedling trays in darkness to accelerate the germination process.
How often should I water Nasturtium seeds?
Water your Nasturtium seeds so that the top 6-inches of the soil always remains moist. Don’t waterlog the potting mix.
Add water to the seedling tray gently and consciously. You can use a spray bottle filled with water to moisten the soil around the seeds.
How long does it take for Nasturtium seeds to germinate?
Nasturtium seeds germinate in 7-12 days provided there are optimal conditions. They take longer to germinate outdoors.
How do you speed up nasturtium seed germination?
Scarification is performed on Nasturtium seeds. It is a process where the seed is nicked slightly so the inner part is exposed.
This helps the seed absorb water quickly as the outer layer is impermeable. Soak the seeds in warm tap water after scarification as discussed above.
What month do you plant Nasturtium seeds?
You can sow Nasturtium seeds anywhere from March to May. You can get flowers before the first frosts if you sow them during this period.
Grow them undercover if you want to sow them in early March. Once it gets warmer you can sow the seeds in a garden bed too.
Sow them undercover if you live in colder areas. You can sow them outdoors if your climate is mild.
Can you Winter sow nasturtium?
Yes, Nasturtium seeds do germinate if they’re sown in winter. You just need to sow them in compost to preserve moisture and provide the seed with nutrients.
Ensure you place the seed at least 2-inch deep in the potting mix. Place the tray such that it gets the optimal temperature.
Can I sow Nasturtiums in June?
Yes, you can sow Nasturtiums in June. Sow the seeds outside in a garden bed that’s well-prepared.
Add a 2-inch compost layer to the garden bed before sowing the seeds. Water the seeds regularly to let them germinate happily.
How many years do Nasturtium seeds last?
Nasturtium seeds that are 3-5 years old can germinate too. In general, germination rates are higher for younger seeds.
You can store Nasturtium seeds for years by storing them in an airtight container. Place this container in the crisper part of the fridge.
Will old Nasturtium seeds grow?
Yes, old Nasturtium seeds grow without an issue provided they’re stored properly. You need to dry them properly before storing them.
The plant that’s grown from old seeds is just as good as the ones planted from new seeds. Just make sure you get seeds from a trustworthy source.
Happy Gardening 🙂