Try to aim for a seed spacing of at least
11.7 inches (30.0 cm) and sow at a depth of around
5.85 inches (15.0 cm).
By our calculations, you should look at sowing Cliff Kidney about 14 days before your last frost date.
As Cliff Kidney is tender, ensure temperatures are mild enough to plant out - wait until after your last frost date to be on the safe side.