Sow at a depth of approx.
0.49 inches (1.25 cm) and aim for a distance of at least
3.12 inches (8.0 cm) between Spinach plants. Soil temperature should be kept higher than
8°C / 46°F to ensure good germination.
By our calculations, you should look at sowing Indian summer about 60 days before your last frost date.
Ensure that temperatures are mild (minimum night temperatures should be around 0°C / 32°F) and all chance of frost has passed before planting out, as Indian summer is a half hardy plant.