When to transplant cold-hardy plants like broccoli, lettuce, and spinach, as well as direct sowing seeds for these plants?

Hardening off: Before transplanting seedlings outdoors, gradually acclimatising them to the outdoor environment is essential. This process is called “hardening off.” Start by placing your seedlings outside for a few hours per day, gradually increasing their time outdoors over a week or so. Ensure they’re protected from direct sun, strong wind, or heavy rain during this period.

Soil temperature: Although cold-hardy plants can tolerate cooler temperatures, they will still grow best if the soil temperature is within their optimal range. For broccoli, lettuce, and spinach, this is typically around 45°F to 65°F (7°C to 18°C). A soil thermometer can help you determine if the soil temperature is suitable.

Frost protection: While cold-hardy plants can handle light frosts, it’s a good idea to have some frost protection measures in place, such as floating row covers or cloches. These can be particularly helpful when transplanting seedlings, as they’re more vulnerable to cold damage than established plants or seeds.

Weather conditions: Pay attention to the local weather forecast and avoid transplanting seedlings during extreme cold or wet periods, which can stress the young plants.

You can generally transplant cold-hardy seedlings around the same time as sowing direct seeds. Still, it’s essential to harden them off, monitor soil temperature, and provide protection from frost and harsh weather conditions.