By: Kayla Wyse
OSU EXTENSION — WILLIAMS COUNTY
faes-williamsextension@osu.edu
May is the month that challenges every Ohio gardener’s timing. Garden centers are full, warm afternoons feel promising, and it’s tempting to plant everything at once. But May is also a transition month, and temperature swings can undo early enthusiasm. Northwest Ohio the average last frost date falls around May 15, yet averages do not guarantee safety. Some years warm quickly; others bring a late cold snap.
Why Dates Aren’t Enough
Instead of relying on the calendar, it’s more accurate to watch nighttime temperatures and soil temperatures. Warm-season crops, such as tomatoes, squash, and beans, need nighttime lows consistently above 50°F. Below that, growth slows and plants may struggle for weeks. Soil temperature matters too. Tomatoes and peppers root best around 60°F, and beans germinate reliably closer to 65°F. A simple soil thermometer removes guesswork and helps avoid planting too early.
What You Can Do In Early May
Even when the weather is unsettled, there’s plenty to accomplish. Cool-season crops—lettuce, spinach, peas, and radishes—perform well. Perennials can be divided, and containers can be prepped. If you bought tender seedlings early, begin hardening them off. Gradually exposing plants to outdoor conditions over a week helps them adjust to sunlight, wind, and temperature changes. When frost is predicted, lightweight sheets, frost cloth, or overturned buckets can protect young plants overnight. Remove covers in the morning to prevent overheating.
When It’s Safe To Plant
By mid- to late May, conditions usually stabilize enough to plant warm-season crops with confidence. Focus on spacing, deep watering, and mulching once the soil has warmed.
The Scarlet Sprout features a new gardening topic each month. If you have specific questions you would like answered in an upcoming column, please contact faes-williamsextension@osu.edu. Until next time, stay curious about what’s growing in our corner of Ohio.
About The Author
Kayla Wyse serves as the Agriculture and Natural Resources Extension Educator for Williams County, where she has been supporting residents since 2023. She holds a Master’s in Plant Health Management from The Ohio State University. Kayla is passionate about entomology, soil science, and helping people feel confident in their gardening and growing skills.
— Information Provided