Early May in Ohio can bring anything from 80°F days to inches of snow on the ground. It is recommended to keep an eye on the forecast paying special attention to the nighttime lows as well as knowing what temperatures your plants will thrive at.
It is recommended to wait until after the Frost-Free Date of May 15th to plant a majority of your annuals and vegetables. However, some plants will benefit from waiting even a little longer to make sure the outside temperatures and soil are warm enough. Geraniums, lantana, coleus, and marigolds can all be planted once we reach the frost-free date. However, vinca, chenille, cosmos, and zinnia all like to have nighttime temperatures above 40°F
Recommended Flower Planting Temperatures:
| Min. Temp | Growing Temp. | |
| Asclepias | 55°F | 70° to 75° F |
| Begonia | 55°F | 65° to 73° F |
| Calibrachoa | 39°F | 55°F to 65°F |
| Chenille | 60°F | 65°F to 80°F |
| Coleus | 35°F | 60°F to 75°F |
| Cosmos | 55°F | 70°F to 75°F |
| Fuchsia | 40°F | 60°F to 70°F |
| Geranium | 32°F | 70°F to 75°F |
| Impatiens | 35°F | 65°F to 70°F |
| Lantana | 32°F | 65°F to 80°F |
| Marigold | 35°F | 70°F to 75°F |
| Petunia | 40°F | 61°F to 80°F |
| Portulaca | 40°F | 65°F to 75°F |
| Vinca | 64˚F | 75°F to 85°F |
| Zinnia | 45°F | 74°F to 84°F |
Onion, kale, spinach, cole vegetables, lettuce, and potatoes all can be planted before the frost-free date, and do better in the colder temperatures. Tomatoes and peppers can be planted as soon as the fear of nighttime frosts past. For the remainder of your vegetable garden including corn, squash, and cucumbers, a low nighttime temperature below 55 degrees can inhibit pollen formation and fruit development.
Recommended Vegetable Planting Temperatures:
| Min. | Ideal. | Max. | |
| Cantaloupe | 60°F | 65°F to 75°F | 90°F |
| Cole Vegetable | 25°F | 60°F to 80°F | 78 °F |
| Corn | 50 °F | 75°F to 86° F | 95°F |
| Cucumber | 60°F | 65°F to 75°F | 90°F |
| Eggplant | 50 °F | 75°F to 85°F | 95°F |
| Kale | 20°F | 60°F to 70°F | 80°F |
| Lettuce | 25°F | 45°F to 75°F | 80°F |
| Onion | 20˚F | 50°F to 70°F | 95°F |
| Pepper | 32˚F | 70°F to 85°F | 90°F |
| Potatoes | 29˚F | 65°F to 80°F | 95°F |
| Pumpkin | 50°F | 65°F to 90°F | 95°F |
| Spinach | 20°F | 50°F to 60⁰ F | 85 °F |
| Summer Squash | 50 °F | 65°F to 75°F | 95°F |
| Tomato | 40°F | 55°F to 85°F | 95°F |
| Watermelon | 42°F | 65°F to 90°F | 95°F |
For all tropical plants like Hibiscus and Mandevilla, you will want to wait till the nighttime temperatures are regularly above 50°F before you leave them out for the summer.
