Although many carnivorous plant seeds germinate within 3-4 weeks, seeds from cold hardy carnivorous plants germinate after 3 to 6 months! Many US-native carnivorous plants produce their seeds in early fall, right before the first frost of the season. If these seeds germinated too soon, the young seedlings would surely die because they wouldn’t have time to fully acclimate to upcoming winter weather. To prevent this from happening, these seeds contain enzymes that prevent them from germinating before the onset of winter.
In order to germinate these seeds, you must expose them to cold damp conditions in order to deactivate the enzymes. When the enzyme is deactivated, the seeds will germinate when the temperature warms up again. This process of preparing seeds for germination is called stratification. Seeds that require stratification include:
• All Sarracenia
• Darlingtonia californica
• Drosera anglica
• Drosera rotundifolia
• Drosera intermedia
• Drosera filiformis
Without stratification, the germination rate would be no more than than 10%. With stratification, the germination rate would increase to 80-100%. Naturally, this will depend on the species. Some species have excellent germination rates, such as Darlingtonia californica
. Other species have low germination rates, such as Sarracenia purpurea
, even with proper stratification.
There are two ways you can stratify your seeds. The first method is by far the easiest and has the fewest risks. It follows the natural rhythm of the seasons. Essentially you sow your seeds in fall and look for seedlings in spring. Use this method if you live in zones 9 or colder.
The second method is best used if you need to germinate your seeds during the off-season, such as spring and summer when it is too warm for proper stratification.
- Harvest your seeds when the seedpods are ripe. If you purchase your seeds from a nursery, ask the nursery when the seeds were harvested. Ideally, you want seeds that are no more than 6 months old. If they are more than 6 months old, make sure the seeds were stored in refrigerators. Under refrigeration, seeds can last for years.
- In fall or early winter, sow your seeds on a standard soil mix of 1 part peat moss and 1 part perlite. Avoid covering up your seeds with soil. Simply sprinkle them on the soil and firmly press down on them with your fingers. (For zones 9 or colder, do this step by early January.)
- Place your pot of seeds outdoors in a tray of water. Set the pot in a tray of water. Throughout the winter months make sure there is always water in the tray. The rain and snow will create the cold damp conditions necessary for germination in spring. Protect your pot if the temperatures go below 20°F (-7°C).
- In early summer look for tiny seedlings. Continue to care for your seedlngs outdoors. Their care is no different than that of adult and juvenile plants. Sprouts are just as cold-hardy as the adults. However, because of their small size, seedlings dry out very quickly, so it is important to pay attention to the water levels in their trays. Sarracenia and Darlingtonia seedlings will reach flowering maturing in 4-5 seasons. Other types of seedlings may reach flowering maturity within 3 growing seasons.
- Lay out a sheet of paper towel on a table. Place your seeds in the center of the paper towel and spread them out evenly.
- To prevent fungal infections, spray your seeds with a fungicide. Either a sulfur-based fungicide or Neem will work. Avoid mineral-based fungicides.
- Carefully wrap your seeds in the paper towel. Don’t wrap them up too much because you want to be able to see the seeds through the paper towel when you hold it up to the light.
- The paper towel will be slightly damp from the fungicide, but you will need to make sure it is damp all the way through. Dunk the wrapped seeds in a bowl of distilled water.
- Place the wrapped seeds in a plastic bag and seal the bag.
- Place the plastic bag and its contents in your refrigerator for four to eight weeks. Check on the bag periodically for signs of mold or fungal infection. Hold it up to the light to make sure your seeds are still healthy. Look for mold and fungus. If mold or fungus develops, immediately unwrap your seeds and spray your seeds with fungicide.
- After four to eight weeks of refrigeration, carefully unwrap your seeds. Allow the paper towel to dry completely before removing your seeds.
- Place your seeds on a soil mix of 1 part perlite and 1 part peat moss and firmly press down on them. Avoid covering up your seeds.
The next step after sowing your seeds depends on the current outdoor temperatures:
- If there is still a risk of frost outside, germinate your seeds indoors in a brightly lit windowsill that receives several hours of direct sunlight. You will see germination within 4 weeks.
- If there is no risk of frost in the next several weeks, place your pot of seeds outdoors in partial sun. You will see germination within 4 weeks, provided that the weather remains warm enough. In most situations, Sarracenia and Darlingtonia seedlings will be 1-2 inches tall at the end of their first season. They will reach flowering maturity in an additional 4 season.
Alternative Indoor Care of Seedlings
You can also grow Sarracenia seedlings indoors for the first two years of their lives, much like you would a tropical sundew. They can forgo winter dormancy for the first year or two of their lives, and because they skip dormancy they can gain size faster.
To care for your seedlings indoors, simply place your pot of sprouted seedlings under grow lights or on an extremely sunny windowsill with a minimum of 4 hours of direct sunlight. (More sunlight is preferable.) Spray liberally with a sulfur-based fungicide weekly to deter mold.
To acclimate them outdoors again, wait until late spring after their second winter (usually 24 months or so after germinating them), putting them outside when temperatures outdoors and indoors are comparable. Acclimate them to direct sun over a period of two weeks by first placing the seedlings in partial shade, moving them gradually into full sun (six or more hours of direct sunlight). They will then grow as outdoor plants for the rest of their lives.
Because of their sunlight and dormancy requirements, avoid growing cold hardy carnivorous plants indoors for more than two seasons.