Temperature

Seeds generally germinate best at temperatures between 65-75°F (18-24°C). Some seeds might require a specific temperature range, so it's wise to refer to the seed packet. If you received gifted seeds or picked them up from your local seed library, you can search for the germination codes online or use this handy tip:

Cool-Season Vegetables: Plants like cabbage, peas, and spinach prefer cooler temperatures for germination, typically around 15°C to 20°C (59°F to 68°F). Most of these don’t need to be started indoors, as you can safely plant them outdoors after the last frost date.

Warm-Season Vegetables: Plants like beans, tomatoes, melons, and peppers thrive with warmer temperatures, usually between 25°C to 30°C (77°F to 86°F). While you can plant beans outdoors a few weeks after the risk of frost passes, some seeds need to be started indoors. See our "Make a Seed Starting Schedule" for further details.

Cold Stratification: Some seeds, especially those of perennial plants and certain wildflowers, require a period of cold stratification (exposure to cold temperatures around 0°C to 5°C (32°F to 41°F)) to break dormancy and initiate germination. It is best to follow their germination codes as indicated on their package or search for the code online.

To aid seed germination, it is advised to place them in a warm spot, such as above a heating air vent or near a heater, or, as we prefer, use heating mats for seed starting. These mats keep the soil warm and are easy to use by plugging them into a power outlet. If you are unsure about your soil temperature, using a soil thermometer can help ensure the soil is within the optimal range for the seeds you're planting.

Once most of your seedlings have emerged, it's generally a good idea to turn off the heat mats to prevent the soil from overheating. At this stage, the seedlings need consistent light and air circulation rather than additional heat. Make sure to adjust your lights as your plants grow!