Most annual flowers are frost-tender. Annual seeds should be sown outdoors after the last average frost date in spring. To get a head start on the season, seeds can be started indoors, and young plants can be set in the garden after the last frost.
Young plants of annuals started indoors should be hardened off before being transplanted into the garden. Harden off plants by exposing them to outdoor temperatures and sunlight for an hour or two each day for several days before transplanting.
Check the weather service or the cooperative extension near you for the average last frost date in spring where you live. Here’s when to start annual seeds indoors and when to set young transplants into the garden.
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- Jump Start Germination Station w/Heat Mat Tray, 72-Cell Pack, Dome
- Espoma Seed Starting Mix
- 200 Count- Jiffy 7 Peat Soil Seed Starting Plugs
- Seed Starter Kit with Humidity Dome (120 Cells Total Tray)
- AgrobriteT5 Fluorescent, 2-Foot, Grow Light System
| Flower | Start Seeds Indoors –weeks before the last frost | Transplant into the garden |
| Ageratum | 6-8 weeks | On last frost date |
| Alyssum | 6-8 weeks | 1-2 weeks after last frost |
| Amaranth | 6-8 weeks | After last frost |
| Bachelor’s Button | 6-8 weeks | On last frost date |
| Calendula | 6-8 weeks | 1-2 weeks after last frost |
| Celosia | 6-8 weeks | On last frost date |
| Coleus | 8-10 weeks | 1-2 weeks after last frost |
| Cosmos | 6-8 weeks | On last frost date |
| Delphinium | 6-8 weeks | 1-2 weeks after last frost |
| Gomphrena | 6-8 weeks | On last frost date |
| Marigold | 6-8 weeks | On last frost date |
| Morning Glory | 3-4 weeks | After last frost |
| Nicotiana | 6-8 weeks | On last frost date |
| Pansy | 8-10 weeks | On last frost date |
| Petunia | 8-10 weeks | On last frost date |
| Pholox | 8-10 weeks | On last frost date |
| Portulaca | 6-8 weeks | On last frost date |
| Salvia | 6-8 weeks | On last frost date |
| Scabiosa | 6-8 weeks | On last frost date |
| Snapdragon | 8-10 weeks | On last frost date |
| Statice | 6-8 weeks | On last frost date |
| Stock | 8-10 weeks | On last frost date |
| Strawflower | 6-8 weeks | On last frost date |
| Sunflower | 3-4 weeks | 1-2 weeks after last frost |
| Verbena | 8-10 weeks | On last frost date |
| Zinnia | 4-6 week | 1-2 weeks after last frost |
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