Cultivars stand for "cultivated varieties". They refer to different types of tea leaf. Although matcha all comes from the same plant (the tea plant - Camellia Sinensis). Each leaf differs slightly from each other. You might have heard that wine has different grape varieties or coffee has different bean varieties, it is just the same with matcha as each leaf variety differs. Each cultivar has different characteristics and flavours. Cultivars can also be blended with each other to create special flavours.
First time purchasing Haru, I loved the Hana, it is very fresh and floral. Perfect for summer or spring. Tastes really well with or without Milk. I will definitely re-purchase.