What is the graft union in grapevines?

• A. The trunk.
• B. The canopy.
• C. The point where two vines are grafted together using a scion.
• D. The root system.

Answer: (C)

At its core, the graft union is the junction where two plant parts are joined and must fuse for the plant to function. In grapevines, grafting links a scion, the grapevine cultivar, to a rootstock with desired root traits. The key is the site where those pieces meet and their vascular cambium aligns, so the xylem and phloem reconnect and nutrients can flow. This is not the trunk, the canopy, or the root system, which refer to different parts of the plant. The graft union is simply the point of contact and fusion between scion and rootstock.