Love roses, but live in a Northern climate? Sub-zero roses are some of the most cold hardy rose bushes available. While many rose plants are hardy to zone 4, most sub-zero roses are able to overwinter in zone 3. These robust plants will add wonderful color to the garden during the summer months. Like other roses, sub-zero roses perform best when they are planted in full sun (six or more hours of direct sunlight daily) and in well-drained soil, rich in organic matter. When selecting sub-zero roses to buy for your garden, some considerations include the rose plant's mature height and spread, its flower color and form, and its fragrance.