Kevin Wiecks, Assistant Horticulturist, prunes the Concord grapevines. Kevin uses a modern pruner to cut the vines back; in the Middle Ages, the Roman pruning knife, the falx vineatoria, was used. (Read more about Roman pruning tools.) In March, the vines are cut back hard to a few outward-facing leaf buds; by midsummer they will have produced a green curtain of foliage on the south-facing wall of the courtyard. If the vines are not pruned early when fully dormant, the sap will run from the cuts like water, although this does not harm the vine. The Concord grapes, which have a tough skin that readily slips from the gelatinous fruit, ripen in October.