This hardy yet delicious leafy vegetable can germinate in soils as cold as 40°F (4°C). Established plants don’t mind temperatures as freezing as 5°F (-15°C)! In zones 6-8, mâche is best direct seeded. The seeds won’t germinate in temperatures higher than 70°F (21°C).
Direct seed miner’s lettuce in soils around 50°F (10°C) about six weeks before your anticipated last frost. These plants don’t mind the cold, but they will die back once the weather warms.
Celery is known for being finicky with weather. To germinate quickly and evenly, the seeds need warm soils around 70-75°F (21-24°C), heating mats help with this. Don't transplant outdoors until temperatures are reliably above 55°F (13°C).
Seeds won’t germinate in soils colder than 70°F (21°C). Start indoors on heating mats or under grow lights about 10-12 weeks before your expected last frost. Maintain consistent moisture and don’t expose plants to temperatures colder than 55°F (13°C).
Pepper seedlings enjoy ambient temperatures around 70°F (21°C) and soil temperatures above 80°F (27°C). If you have heating mats, it’s best to reserve them for your favorite pepper plants.
Most tomato seeds germinate best at soil temperatures around 80-90°F (27-32°C). A heating mat is helpful! Avoid starting tomatoes too early, or you may end up with rootbound, leggy, wimpy seedlings that don’t take off very quickly once in the ground.
While broccoli is a cold-weather crop, the seeds still prefer warmth to germinate. Soil temperatures around 75-80°F (24-27°C) are ideal, with an ambient temperature around 60°F (16°F).