Keep in mind when planting that Clear crystal is thought of as half hardy, so it will need protecting in periods of cold weather.
Aim to sow
0.0 inches (0.0 cm) deep and try to ensure a gap of at least
8.97 inches (23.0 cm). Soil temperature should be kept higher than
18°C / 64°F to ensure good germination.
By our calculations, you should look at sowing Clear crystal about 90 days before your last frost date.
As Clear crystal is half hardy, ensure temperatures are mild enough to plant out - wait until after your last frost date to be on the safe side.