Answer: Most hybrid roses are grafted onto a vigorous root stock. This graft is called the bud union and it is usually just above the roots. You can identify it because it is a swollen area on the main stem. A bud union is more frost sensitive than the top or the roots of a rose so it's a good idea to plant a rose with the bud union buried in the soil, or to protect the bud union with mulch over the winter months. Hope this answers your question!
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