Arugula, Slow Bolt - Herb Seeds: 43 days. Contains approximately 750 Arugula Herb Seeds. Germination: 5-7 days at 40-60 F. Soak seeds in warm water for 6-8 hours. Plant seeds very shallow and keep moist. A member of the mustard family, Arugula is a leafy annual herb plant that looks similar to lettuce.