Soil temperature for Corn


It’s been a cold Spring in Toronto? Is the soil warm enough now to plant corn?


Thanks for contacting the Toronto Master Gardeners.

Given the variable weather conditions that Toronto has experienced this spring, knowing when to plant what can be difficult. The optimal soil temperature for planting corn should be above 50’F (10’C.). One can use a soil thermometer (or meat thermometer) to check the temperature of the soil where you plan to grow the corn–soil temperatures vary–raised beds vs. ground soil. On May 17th, 2020, the soil in my garden is slightly above the recommended temperatures.

However, soil temperature is not the only consideration when planting corn–the amount of moisture in the soil is key. “Seed germination is a two-step process. The first step is imbibing water; a corn seed absorbs about 30% of its weight in water. Absorption of water is not dependent on the temperature of the water or soil. The second step of germination, which does depend on soil temperature, is the growth of the radicle root and coleoptile shoot. If temperatures are below 50°F., initiation and growth of the radical and coleoptile will not occur or will be very slow.”

Given the fact that most soils in Toronto are now moist due to the recent rainfall, that the soil temperature is now above 50’F, and that the air temperatures will be upwardly stable for the next while, planting corn seeds now would be recommended.

We wish you great success in growing corn this season.