The most fundamental botanical difference lies in the root system's origin. An own-root rose is a genetically identical plant grown from a cutting of the original cultivar. The entire plant—roots, canes, and flowers—shares one DNA profile. In contrast, a grafted rose is a composite of two different plants: the scion (the top portion of a desired cultivar chosen for its blooms, fragrance, and form) is physically fused onto the rootstock (the lower portion and root system of a different, specially selected rose species or cultivar chosen for its vigor and disease resistance). The resulting plant is a chimera of two distinct genetic identities.
The choice of rootstock directly influences the grafted plant's performance. Rootstocks like Rosa multiflora or Dr. Huey are selected for their aggressive, widespread root systems that confer superior vigor, drought tolerance, and nutrient uptake. This can lead to a faster-establishing, larger plant in the initial years. For own-root roses, the growth habit is intrinsic to the cultivar itself; it may be slower to establish as it builds its own root system but will grow true to its natural size and form. Regarding hardiness, if the graft union (the swollen knob near the base) is not adequately protected in winter, the cold-sensitive scion can die back, and the rootstock may send up its own, often undesirable, suckers. An own-root rose, if killed to the ground by cold, will typically regenerate true to the original cultivar from the roots.
From a physiological perspective, the graft union represents a potential point of vulnerability. It can be a site for disease entry or mechanical failure over many seasons. Furthermore, some long-term compatibility issues can arise between the scion and rootstock. Own-root roses avoid this potential weakness entirely, as there is no graft union. Their longevity is a function of the cultivar's natural lifespan. Concerning diseases like rose rosette disease (RRD), a devastating virus, the response differs significantly. If an own-root rose contracts RRD, the entire plant is affected and must be removed. In a grafted rose, the rootstock is often a species highly susceptible to RRD. Even if the scion is removed, the infected rootstock can persist, serving as a reservoir for the disease to spread to other roses via mites.
Suckering is the growth of shoots from the root system. In grafted roses, this almost always means the suckers are from the rootstock, not the desired scion. These suckers are morphologically distinct—often with different leaf shapes, thorn patterns, and inferior flowers (like the common deep red blooms of Dr. Huey)—and they divert energy from the scion. They must be identified and removed at their point of origin below the graft union. Own-root roses may also produce suckers, but these are true to the cultivar and can be left to expand the plant or be shared with other gardeners, as they are genetically identical.
