Iris seeds are slow to germinate (28 to 35 days) and are subject to decay before they can get going. This is why we recommend planting 3 to 5 seeds per location, and then thinning them as they get established.
- Seed Treatment: Cold stratify your iris seeds for 30 to 60 days to trigger germination. Some guides recommend dunking the seeds in boiling water for about a minute at the end of the stratification process.
- Planting Depth: 1/16” to 1/8"; iris seeds require sunlight to germinate.
- Starting Indoors: Prepare biodegradable pots with a sterile seedling mix, and plant 3 to 5 treated seeds in each container. Place containers under artificial light in a 65°F to 70°F room, cold frame, or greenhouse.
- When to Plant Outdoors: Direct sow your iris seeds as soon as all danger of frost has passed.
- Seed Spacing: 18" in any direction. Map out a "zigzag" pattern to create staggered rows for the best effect.
- Days to Germination: 28 to 35 days
- Transplanting Tips: Plant the seedlings, biodegradable pots and all, being careful not to disturb the growing rhizomes. Give the pots a good soaking before you do, and consider gently scoring the sides to help the root system "break out."