Starting Cosmos From Seed Indoors

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Dreaming of a vibrant cottage garden without the hassle? This guide shows you how to grow the stunning cosmos flower from seed to bloom. Learn how to start cosmos seed indoors with these easy tips.

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Supplies – Cosmos Seeds – Vermiculite – Seed Starting Potting Soil – Seed Trays – Bottom or Drainage Trays – Clear Dome Lids – Grow Lights - Shelf System - Heat Mat - Plant Labels - Oscillating fan - Programmable Timer

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Cosmos can be started indoors about 2-4 weeks before the last frost date in your locality. Use a seed starting tray or small pots with drainage holes filled with a quality organic seed starter mix that is pre-moistened.

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Make a small hole then sow the seeds then lightly cover them with vermiculite. Sow only one variety per cell tray as the different plants will germinate at different times.

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Cover seed trays with a clear dome and move them under the grow lights on a heat mat to speed up germination. They typically germinate within a few days to a week.

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Remove the cover when the seeds start to germinate. It’s OK if they didn’t all germinate, more will grow after the cover is removed. Keep soil moist by bottom watering only

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Before transplanting cosmos seedlings outdoors, harden them off by gradually exposing them to outdoor conditions over a period of 14 days.

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When seedlings are hardened off and ready to plant in the garden, space cosmos transplants in your flower garden about 9 inches apart after the last frost date. Spacing is really important so there’s enough airflow between plants to prevent problems like powdery mildew.

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Follow along to learn more about how to grow cosmos flower from seed.

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