When one desires to move old plants it is possible to reduce the shock to them in either of two ways. The simpler is by driving a spade down vertically to its full length of blade about twelve or fifteen inches from the plant and repeating the process in a circular form until all lateral roots have been cut. This should be done in June or early July and the plant should be moved two or three weeks later. Dig a sloping hole leading to the vertical spade-cuts on one side, remove some of the surface soil round the plant to reduce weight, drive the spade under the plant, and gently lift it in a ball of earth. The ball can be made more adherent by wetting and dabbing the outside of it. Slide it into its new hole by way of another sloping cut, fill the spaces round the ball with friable soil and water it heavily. The plant must be pruned and all leave carefully clipped off to reduce loss of moisture and consequent shrivelling.
The less simple way is to prepare the rose for the move by digging a trench in early spring in a semicircle round the plant at a radius of a foot, or slightly more, from the stem, depending on the size of the plant. This will cut the roots in that part. Fill the trench with loam that is of good quality but does not contain fermenting manure of any type. A network of fibrous secondary roots will form and permeate the rich new soil. After three months, about Christmas time, complete the circle in a similar manner. In the autumn, about four months later, the plant can be lifted with a good ball of earth held together by a mass of fibrous roots. The plant has really been root-pruned in either method of transplanting. This more involved method is necessary only when moving a very large old rose plant.
By cutting any strong root at a reasonable distance from a plant one forces the growth of many smaller ones of the feeding type. Roots feed only through their terminal points, and so the greater the number of small fibrous roots the better a plant can feed from the soil. Soil food consists of water and various minerals salts. These are carried in the sap to the leaves, which, by photosynthesis, manufacture the substance of the plant from the water, carbon dioxide, and minerals. This process fails if the soil nutrients are not in well-balanced proportions.
Rose roots often exceed four feet in length, but this is much less important than masses of fibrous roots. The lighter and looser the soil, the larger the root system, probably because food is more scattered in light soil and because the plant needs stronger anchorage. Fresh rootlets are formed each year. Older roots act merely as conduits for water and soil-derived nutrients. Old plants may sometimes be rejuvenated by root-pruning, by following the second method for transplanting, except that the plant is not moved. Probably the new soil added in the trench round the plant is even more helpful than the severing of the roots. You can find info about plants-care with https://apps.apple.com/us/app/plantspot-plant-identification/id1437376141 app, free on itunes for your iphone.