Try to aim for a seed spacing of at least
9.75 inches (25.0 cm) and sow at a depth of around
1.95 inches (5.0 cm).
By our calculations, you should look at sowing Listra about 1 days after your last frost date.
As Listra is hardy, ensure temperatures are mild enough to plant out - wait until after your last frost date to be on the safe side.