| Plant | Zone 4a | Zone 4b |
|---|---|---|
| Zinnia | Plant outside: May 19 to Jun 23 Start seeds indoors: around Apr 21 | Plant outside: May 15 to Jun 19 Start seeds indoors: around Apr 17 |
| French marigold | Plant outside: May 19 to Jun 23 Start seeds indoors: around Apr 7 | Plant outside: May 15 to Jun 19 Start seeds indoors: around Apr 3 |
| Petunia | Plant outside: May 19 to Jun 23 Start seeds indoors: around Mar 10 | Plant outside: May 15 to Jun 19 Start seeds indoors: around Mar 6 |
| Cosmos | Plant outside: May 19 to Jun 23 | Plant outside: May 15 to Jun 19 |
| Sunflower | Plant outside: May 19 to Jun 23 | Plant outside: May 15 to Jun 19 |
| Impatiens | Plant outside: May 19 to Jun 23 Start seeds indoors: around Mar 24 | Plant outside: May 15 to Jun 19 Start seeds indoors: around Mar 20 |
| Wax begonia | Plant outside: May 19 to Jun 23 Start seeds indoors: around Feb 24 | Plant outside: May 15 to Jun 19 Start seeds indoors: around Feb 20 |
| Zonal geranium | Plant outside: May 19 to Jun 23 Start seeds indoors: around Mar 24 | Plant outside: May 15 to Jun 19 Start seeds indoors: around Mar 20 |
| Snapdragon | Plant outside: Apr 14 to May 12 Start seeds indoors: around Feb 17 Fall planting: Aug 10 to Sep 7 | Plant outside: Apr 10 to May 8 Start seeds indoors: around Feb 13 Fall planting: Aug 13 to Sep 10 |
| Pansy | Plant outside: Apr 14 to May 12 Start seeds indoors: around Feb 3 Fall planting: Aug 10 to Sep 7 | Plant outside: Apr 10 to May 8 Start seeds indoors: around Jan 30 Fall planting: Aug 13 to Sep 10 |
| Sweet alyssum | Plant outside: Apr 14 to May 12 Fall planting: Aug 10 to Sep 7 | Plant outside: Apr 10 to May 8 Fall planting: Aug 13 to Sep 10 |
| Celosia | Plant outside: May 19 to Jun 23 Start seeds indoors: around Apr 7 | Plant outside: May 15 to Jun 19 Start seeds indoors: around Apr 3 |
| Scarlet sage | Plant outside: May 19 to Jun 23 Start seeds indoors: around Mar 24 | Plant outside: May 15 to Jun 19 Start seeds indoors: around Mar 20 |
| Lantana | Plant outside: May 19 to Jun 23 Start seeds indoors: around Mar 10 | Plant outside: May 15 to Jun 19 Start seeds indoors: around Mar 6 |
| Madagascar periwinkle | Plant outside: May 19 to Jun 23 Start seeds indoors: around Mar 10 | Plant outside: May 15 to Jun 19 Start seeds indoors: around Mar 6 |
| Nasturtium | Plant outside: May 19 to Jun 23 | Plant outside: May 15 to Jun 19 |
| Sweet pea | Plant outside: Apr 14 to May 12 Fall planting: Aug 10 to Sep 7 | Plant outside: Apr 10 to May 8 Fall planting: Aug 13 to Sep 10 |
| Larkspur | Plant outside: Apr 14 to May 12 Fall planting: Aug 10 to Sep 7 | Plant outside: Apr 10 to May 8 Fall planting: Aug 13 to Sep 10 |
| Pot marigold | Plant outside: Apr 14 to May 12 Fall planting: Aug 10 to Sep 7 | Plant outside: Apr 10 to May 8 Fall planting: Aug 13 to Sep 10 |
| Coleus | Plant outside: May 19 to Jun 23 Start seeds indoors: around Mar 10 | Plant outside: May 15 to Jun 19 Start seeds indoors: around Mar 6 |
| Garden verbena | Plant outside: May 19 to Jun 23 Start seeds indoors: around Mar 24 | Plant outside: May 15 to Jun 19 Start seeds indoors: around Mar 20 |
| Spider flower | Plant outside: May 19 to Jun 23 | Plant outside: May 15 to Jun 19 |
| Floss flower | Plant outside: May 19 to Jun 23 Start seeds indoors: around Mar 24 | Plant outside: May 15 to Jun 19 Start seeds indoors: around Mar 20 |
| Moss rose | Plant outside: May 19 to Jun 23 | Plant outside: May 15 to Jun 19 |
Zones measure winter cold, not season length, so your own frost dates can be a week or two off the zone median. Look up your frost dates by ZIP code, or read all about zone 4a.
Hardiness ranges, light and size are typical figures from university extension services and botanic garden plant records; a named variety can differ, so check its tag. Planting dates come from each zone's median frost dates (NOAA 1991 to 2020 climate normals) and the timing rules in how we check.