Penn State Master Gardener Practice Exam

The essential factor in a successful graft is aligning the cambial layers. The cambium is the thin, living tissue just inside the phloem and just outside the xylem that continuously divides to form new vascular tissue. When the cambial layers of the scion and rootstock are in contact, they can fuse and create a continuous vascular cambium between the two pieces. This connection allows the movement of water, minerals, and sugars across the graft as healing proceeds, enabling the graft to grow together.

If the cambial zones don’t meet, you can still have surface contact or some tissue touch, but there won’t be a continuous vascular connection. The epidermis acts mainly as protection, while phloem and xylem are components of the transport system; without cambial alignment to generate new vascular tissue across the union, long-term graft success is unlikely.