About rose bud

Roses are propagated commercially in one of two ways. The most common method is to take a bud from a desired cultivar and graft it onto a species rose rootstock. Rootstocks used are often Rosa multiflora, Rosa canna, or Rosa laxa. These are selected because of their ability to produce vigorous root systems. The place where the cultivar and rootstock are joined becomes distinctively swollen. This is referred to as the bud union or "nob." All canes of the cultivar come from the bud union.

From a gardener's point of view, this produces a rose that tends to have a better root system. From a nurseryman's point of view, budding results in plants that reach the market quicker. Less time is spent in the production fields.
There are several pitfalls to be aware of with budded roses. Rootstocks of budded roses often send up suckers that produce leaves and flowers that are totally different from the budded cultivar. Suckers are also a common result when budded roses are killed to the ground during severe winters. That is why some roses mysteriously change identities between seasons, producing long, thin canes with different leaves and different flowers. Other problems that can occur are graft incompatibility, resulting in reduced vigor and death, as well as the transmission of rose mosaic, a virus infection that reduces the rose's performance. Budding is often the only option in commercial production since not all roses can be successfully rooted or produce a very poor root system on their own. Budding may also be the only way to maintain a specific cultivar.
The other method of propagation is softwood cuttings, producing roses offered as own-root roses. Many of the old garden roses are offered as own-root roses and provide distinct advantages, especially for northern gardeners. With own-root roses, the problem of off-type suckers disappears because all shoots coming from the base of the plant are identical to the cultivar that you purchased. Plants grown on their own roots also tend to be longer-lived. Also, since the root system is genetically identical to the canes, one is assured that the new basal canes produced each year are true to the cultivar. This is especially important where severe winters often kill roses to the ground. Own-root roses may be slow-growing initially and may be smaller in size and less robust, but they soon develop into very durable plants.
Many roses, both modern and old garden roses, are now offered as either budded or own-root roses. Suppliers should be able to tell the gardener what type of plants they offer. Some nurseries even offer custom budding or rooting services for some very difficult-to-find roses.