How To Cold Stratify Seeds
Some types of seeds germinate best after a period of what is known as cold stratification or cold moist stratification. While the term may seem daunting, it is easy to do at home.
- Choose a sterilized growing/germinating medium such as seed starting mix, sand or a paper towel.
- You can easily sterilize the medium yourself using boiling water. It should be moist but not soaking wet.
- Allow the medium to cool, then place it in a resealable plastic bag or other airtight container, along with the seeds you want to stratify.
- Seal the bag or container and refrigerate for the recommended stratification period of the seeds.
- Make sure to date and label each container!
- Seeds germinate in 7-14 days.
- Direct seed after all chance of frost has passed and soil has reliably warmed. You can start indoors 3-4 weeks before transplanting, but be careful not to let plants become pot bound.
- Planting depth will vary depending on seed size, as sunflower seed sizes range widely. A general rule of thumb is to plant seeds twice their own width, so a seed that is 1/2 inch wide should be planted 1 inch deep. Most sunflowers are planted at 1 inch deep.
- Ideal germination temperature is 70-75 F.
- Prefers full sun.
- Provide light, well-drained soil.
- Excessively nitrogen-rich soil will adversely affect blooming.
- Space multi-branching types 18-24 inches apart and single-headed/ dwarf varieties just 4-6 inches apart.
- While sunflowers are fairly disease-free and hardy, they are susceptible to white mold. To prevent this, keep foliage dry and provide well-drained soil.
- If borers infest your sunflowers, spray leaves thoroughly with organic approved insecticidal oils when the adult insects are present and laying eggs on the leaves.
Saving sunflower seeds is very easy!
- When petals die back and heads begin to dry and turn brown, place a paper bag over the heads to protect seeds from birds.
- After a few days, the heads will dry to a dark brown. Bring the heads indoors and hang upside down in a dry area in direct sunlight for up to a week, shaking seeds free each day.
- Store in a cool, dark, dry place.