Keep in mind when planting that Grandmother's Garden is thought of as hardy, so this plant will survive close to or on freezing temperatures.
Soil temperature should be kept higher than
18°C / 64°F to ensure good germination.
By our calculations, you should look at sowing Grandmother's Garden about 56 days before your last frost date.
As Grandmother's Garden is hardy, ensure temperatures are mild enough to plant out - wait until after your last frost date to be on the safe side.