Vein pairs help to determine the maturity as well as its identity. The petiole that extends into the leaf divides the leaf into 2 equal parts, on each side of the midrib are matching pairs of veins. To count the vein pairs start at the tip and count the veins on 1 side of the blade all the way to the base. Vein pairs are just another way to help identify a plant. It may not be worth it if it requires a lot of time to add to the database, there are other sources that have the info, like the Hosta Library.
