Everything You Need to Know About Osiria Roses

If you've ever seen an Osiria rose, then you already know why they're so unique. An Osiria rose is a hybrid tea rose that produces dramatically two-toned flowers with a heady fragrance. Many think this vibrant rose is artificial, but it is indeed a real rose, though it is not readily found in most common garden centers. If you are interested in growing them in your rose garden, it helps to understand that they are not easy plants to care for. However, if you're up for the challenge, we asked gardening experts for their advice about how to plant, care for, and prune Osiria roses for the best blooms.

What Do Osiria Roses Look Like?

"You can identify this rose by a clear color contrast between the exterior color of the rose petals and its interior," says Andrea Scharff, a master gardener and landscape designer. "It is most often found with a cherry red petal and a white reverse."

How to Grow Osiria Roses

As beautiful and interesting as Osiria roses are, growing them is no easy feat. "The Osiria rose can be challenging to grow," says Benjamin Godfrey, garden manager at Cornerstone Sonoma. "It's a slow grower that's susceptible to powdery mildew, black spot (fungus), and weak stems; but for those who are patient and take good care of it, the Osiria rose can reward them with florist-worthy, large, beautiful flowers that have a delightful fragrance."

Here are general guidelines to help you grow and care for Osiria roses.

Sunlight

Since Osiria roses are a relatively short and slow-growing plant, Godfrey says it's best to plant them in an area that receives full sun; you'll also want to choose a spot that is protected from strong winds and pelting rain. "It will also do okay in partial shade, but having more sun will equate to more growth, thicker stems, and more big, beautiful flowers," he explains.

Soil

Ensure your Osiria roses have good soil drainage. Godfrey suggests digging a hole in your garden that is one-third to twice as wide, and equally deep, as the container you're removing the rose bush from. "Before planting, it's best to slightly mound the soil so it drains well," he says. "Make sure not to plant your Osiria in a low spot, because without good drainage, it is susceptible to root rot." He also recommends planting it so that the trunk is level with the soil around the hole. "If you bury the trunk, it will be susceptible to fungal infection," he adds.

Watering

As a rule of thumb, Scharff says if you live in a location with extremely hot temperatures, you should water your Osiria roses every day. "However, on a standard summer day with decent heat, you will need to water every two or three days, and in warm, dry weather, you will only need to water about once a week." To ensure your Osirias get thoroughly watered, Godfrey suggests waiting until the top 2 or 3 inches of soil are dry between waterings.

Fertilizing

To encourage vigorous growth and abundant blooms, Scharff says Osiria roses should be fertilized two or three times a year. "Fertilizer applications can be made in early spring, immediately after pruning, during the first bloom period, and in mid to late July—but not after July 31," she says. "In early spring, raking a one-inch layer of well-composted steer manure (or a 2-1-2.4 fertilizer) into the soil around established roses provides the nutrients they need to develop foliage and flowers."

Pruning

When pruning or deadheading Osiria roses, Godfrey suggests following these steps:,

• Cut back 1/4 to 1/2 an inch above a leaf that has five petals. "The stem should be at least the width of a pencil so that the new growth will be able to support the weight of a flower," he explains.
• Choose a five-petal leaf that is facing outward. "Cutting above an inward-facing leaf results in a cane that crosses other branches and grows into the center of the bush," says Godfrey.
• "Cutting the stem at an angle prevents any water from pooling on the end of the stem, reducing the risk of infection," he says.