Stephen Albert
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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- Seed Starter Kit with Humidity Dome (120 Cells Total Tray)
- AgrobriteT5 Fluorescent, 2-Foot, Grow Light System
When to seed start and transplant annuals
Here are annuals you can seed start indoors before the last frost in spring. Click on the flower name in the left column to learn how to plant and grow these colorful annuals:
| 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 |
Also of interest:
When to Seed Start Annual Flowers
24 Annual Flowers to Plant in Summer
How to Care for Annual Flowers
Growing Annual Flowers for Summer Bloom
Easiest Annual and Perennial Flowers to Start From Seed
