Zinnia seeds do not need to freeze in order to germinate. Zinnia plants can reseed (self-sow) without needing a cold period. Zinnia seeds do not need cold treatment to germinate.
Zinnia seeds can be harvested and saved indoors until they are ready to be planted outside, and do not need to be kept cold while stored.
What Does Zinnia Reseed mean?
According to Merriam-Webster dictionary, there are a couple meanings for the term reseed when used in this context:
1) to maintain itself by self-sown seed*
You may see reseed used interchangeably as self-sow or self-seed. Zinnias can drop mature seeds to the soil that will reseed (self-sow) and grow new plants without any human intervention.
2) to sow seed on again or anew*
This refers to the act of planting the seeds. You can harvest Zinnia seeds, and reseed in the spring after threat of frost has passed.
When Do You Plant Zinnia Seeds?
1 to 2 weeks after your average last frost date seeds can be planted directly outdoors. The ideal soil temperature for zinnia seed germination is 70-80 degrees F.
Start indoors 5-7 weeks before your average last frost date, and transplant outdoors after last frost. Zinnias are sensitive to transplanting, so make sure your plants are well developed and properly hardened off before planting outdoors.
What is a last frost date? See explanation at What Is A Frost Date?
Not sure what your last frost date is? Enter your zip code in this easy Zone Locator to find last and first frost dates for your location.