Original: Italian growers have found that planting corms deep and in rows spaced 2 - 3 cm apart optimizes thread yields, whereas planting depths of 8 - 10 cm optimizes flower and corm production.
Simplified: Growers have found that planting corms deep and in rows spaced 2 - 3 cm apart makes more threads, whereas planting depths of 8 - 10 cm makes more flowers and corms.