Tender Annuals to Winter Sow

Tender Annuals - Group 3

Group 3 seeds require higher temperatures to germinate and are extremely sensitive to cold.

Timing

Seeds from tender annuals do not benefit from sitting in cool damp conditions like seeds from group 1 and 2. Aim to start these seeds in the weeks leading up to your last frost date.

For slow growing tender annuals (like petunias and tomatoes), start these around 6-8 weeks before your area's average last frost date. Aim to start fast-growing annuals (like zinnias and basil) anywhere from 3-6 weeks before your area's average last frost date.

Care

Monitor soil moisture before germination and as seedlings continue to grow.

When nighttime temperatures are forecast to drop into the thirties, protect your group 3 seedlings from frost damage.

First, ensure the soil is thoroughly moist—wet soil retains heat much better than dry soil and freezes more slowly.

Second, cover seedlings with frost cloth or blankets to shield them from freezing temperatures that could damage or kill tender plants.

Alternatively, if you have space available, move containers into a greenhouse or garage overnight. Immediately move to a sunny location when temperatures rise above freezing the following day.

On days where temperatures are forecast to be in the upper 80s for multiple hours, place winter sown containers in an area that gets morning sun and afternoon shade. When temperatures reach the 90s, place jugs in shade and break the seal for additional airflow. Do not open the top portion of the container completely as this puts the soil at risk for drying out more quickly resulting in lost seedlings. Soil moisture is especially important on these very warm days.