A result of a cross between hybrid tea and floribunda roses, grandiflora-type roses were born of necessity, because the resulting plants didn’t fit in either of the parent categories. Featuring habits of both parents, grandifloras are known for their showy, high-centered blooms similar to their hybrid tea parentage, as well as their taller plant height. From their floribunda parent, grandiflora roses sport multiple blooms per stem, unlike hybrid tea roses. The pioneer of this group of roses was the beautiful ‘Queen Elizabeth’ in 1955.
Grandiflora roses add a splash of color (in a wide variety of hues) to the garden along with their lovely scent. Because of their tall and fairly sparse growth habit, grandiflora roses fit in well among other perennials and shrubs. Position them so you can enjoy their fragrance throughout the day and into the evening.
Grandiflora Rose Care Must-Knows
Like all other rose types, grandiflora roses need full sun. With anything less, you increase the probability of numerous problems, such as fewer blooms, more stems flopping over, and overall weak, sparse plants. Foliar diseases are the biggest problem for many roses, and grandifloras are very susceptible to all the most common ones that plague roses. One of the worst is black spot, a fungal disease that causes dark spots on the foliage. In many climates, black spot is almost inevitable for rosebushes. The best thing to do is to be proactive and plant in full sun, prune properly for good air flow, and avoid getting the foliage wet when possible. Mildews are also troublesome, including powdery and downy varieties. Control these as you would black spot.
Grandiflora roses generally will survive in full sun and in well-drained soils. If you have poor soil, amend it by adding a good amount of general purpose potting mix and peat moss to help lighten it up. Once you have dug the hole for your rose plant, gently spread the roots over a mound of soil and fill in with the amended soil, filling any gaps and packing down lightly to remove any air pockets around the roots. Many grandifloras are grafted plants, meaning the top growth is actually a separate plant from the roots. When planting grafted roses, make sure the graft union (the bulging knob-like spot near the base of the plant) is buried 1 to 2 inches below the soil level in northern climates, and just above the soil in warmer climates. Prune back any stalks emerging from below this union; otherwise you risk the more vigorous rootstock taking over your beautiful top variety.
Related: Prune Your Roses Right
Once planted, make sure to water well at the base of the plant. As the plant grows, make sure to continue watering regularly until established. Roses are heavy feeders, so plan accordingly; repeat blooming varieties will be happy with regular doses of fertilizer.
Pruning Grandiflora Roses
Pruning grandiflora roses is the same deal as hybrid teas. If you're not familiar, it is best to prune in late winter, before the plants have put on their new spring growth. At this point, remove any old, dead growth and diseased wood. Long, vigorous shoots can then be cut back to 4 to 6 buds from the base, which is generally 10 to 15 inches above the graft union. After a harsh winter, you may have substantial dieback on these long canes; simply cut back to the first signs of live wood. As plants get older and canes get thick, you may need to cut some of these older canes almost back to the ground. This will help to encourage new growth from the base of the plant, and can also help to increase airflow.