Rapitest Soil Thermometer and soil temperature ranges for over 25 types of plants.
Transplanting shock in seedlings can be avoided if the soil temperature is checked before planting. Most seeds require a warm soil to a depth of at least 3 inches (8 cm) in order to encourage germination. Planting by the calendar disregards weather variations from year to year. Timing planting based on soil temperature helps assure plants get a good start. Plants that have been planted in soil that is too cold exhibit symptoms similar to those planted in soil that has poor nutrient values. Once the soil warms up, they begin to grow vigorously if they have survived the cold conditions.
Insert thermometer to a maximum depth of 2-3 inches (5-8 cm) in the soil. Check the temperature recorded after 3 minutes.