Frost bitten plant
Frost bitten plant
The common saying that “Ohio weather presents all four seasons in one week” has once again proven to be true! Some parts of Ohio experienced considerable rainfall events, freezing temps, snow cover, and hail since last  Friday evening. Putnam County experienced a hard freeze Friday evening and an additional two nights of freezing temps this week. Thankfully, the extended forecast indicates warmer temps in our very near future.

Farmers and gardeners may be concerned about how low soil and air temperatures affect plants and seeds in the ground. Compared to this time last year, our soils are quite dry and planting progress for field crops and gardens has been good. Not many fields have emerged corn or soybean plants, so the risk of freeze damage to the growing plant has been low.

Of perhaps greater concern is how cool soils (generally considered to be below 50°F) will affect germination and emergence of both corn and soybean. Laura Lindsey addresses this topic in the current CORN newsletter found at Current daily average soil temperatures at the OARDC weather station near Custar ranged from 46 to 50°F over the past week.

Corn can tolerate low soil temps of 28 to 32°F before injury or death occurs. Since our local soil temperatures hovered around 38°F early Saturday morning while air temperatures dipped to 26°F, damage to corn is not very likely. However, farmers will want to walk their fields and look for signs of damage in emerged or germinating seed early next week.

Similarly, farmers will want to walk their wheat fields next week to look for signs of freeze injury. Most of the county’s wheat crop is at Feekes growth stage 6 to 7 where the developing head is protected within the crop canopy. More advanced fields beyond Feekes growth stage 8 may have damaged heads. If still in the boot, the head may be twisted or distorted and emerged heads will become blanched and not fill. Both conditions result in loss of yield.

Gardeners and homeowners have likely found that covering tender plants is not always easy nor successful. Tender plants such as those newly germinated or transplanted from a greenhouse or warmer setting are most susceptible to damage. However, many landscape plants including herbaceous perennials newly emerged from the soil as well as shrubs and trees with open flowers and flower buds may also be affected.

There are three types of low temperature injury in plants. The first is called chilling injury – which happens generally when warm-season and tropical plants are exposed to above-freezing temperatures. A good example is when basil leaves are harvested from the garden and placed in a refrigerator. The leaves quickly darken from green to purple due to the low, but non-freezing temperatures.

Frost injury occurs on clear, cool nights when plants radiate heat to the air around them. This cools the plant and allows water to freeze on the plant surface as ice crystals. Temperatures do not have to be freezing for frost injury to occur, and frost injury does not always result in significant plant damage.

Freeze damage, however, is when cold air reduces the temperature inside the plant to at or below freezing for extended periods of time. This causes water within the cells to expand and rupture, causing the contents of the cell to spill out resulting in cell death. Plants damaged by freezing temperatures turn brown and have a mushy, water-soaked appearance.

Hopefully after this week, Putnam County will be in the clear of potential freezes. The average last frost-free date for our area is May 15. The latest freeze date on record since 1982 at the weather station in Custar was May 19. Here is to warmer temperatures in our future!

For additional information while the Extension Office is currently closed due to COVID-19, please contact us at 419-523-6294 or by email at You can also find us on Facebook by searching for OSU Extension Putnam County.