Plant Parenting: Some Plant Cuttings Need a Callus
July 27, 2019
A callus often develops at the base of a cutting at the site of a wound, when conditions are good for rooting. A callus will look like a knot or knuckle growing at the base of a cut stem or leaf.

This pepper cutting has developed a knuckle-like callus at the base of the cut stem; crown roots will soon develop.
PC: Leslie F. Halleck
Some plants will develop a callus and adventitious roots simultaneously, while other plants must first develop a callus first, before new roots can grow.
Learn more in my plant propagation book PLANT PARENTING