When selecting a graft union, what is a key sign of good compatibility?

• A. A loose union
• B. A thick bark around the graft
• C. No vascular connection
• D. A tight, calloused union with successful vascular connection

Answer: (D)

A successful graft hinges on the cambial layers of the scion and rootstock aligning and fusing, so the best sign is a tight, calloused union that shows a functioning vascular connection. When the cambium of both pieces touch, they proliferate to form a continuous callus across the joint, and xylem and phloem tissues connect, allowing water and nutrients to move freely between the parts. This snug, well-formed bridge indicates good compatibility.

If the union is loose, there are gaps and poor cambial contact, which interrupts vascular continuity and undermines the graft’s chances. A thick bark around the graft can hide the underlying cambial interface and does not guarantee proper fusion. No vascular connection directly means the graft cannot transport water and nutrients, signaling failure.