How to Grow and Care For Osiria Rose

Osiria rose (Rose x hybrida, Rose 'Osiria') is a bi-color hybrid tea rose. It is a member of the Rosaceae genus, created in Germany in 1978 primarily as a florist rose. Osiria rose is a cross between Tea rose and the hybrid 'Perpetual' rose.

This fragrant rose features deep, intense hues of red or burgundy on the inside petal with a sharply contrasting white on the outside and sometimes at the petal base. It's a slow-growing, high-maintenance shrub, that grows to four to five feet tall at maturity and has a vulnerability to pests and disease. Picky about growing conditions, the Osiria rose is highly sought after as a stand-out in the garden for its contrasting 4-inch flowers. You will need to search specialty nurseries and plant retailers to find an established Osiria rose. If you love to grow roses and enjoy a challenge, here's how to care for this stunning bi-color hybrid tea rose.

Warning

While seeds that claim to include Osiria rose may be easier to find than the plant itself, don't expect to end up with blooms similar to the rose you were looking to grow. Osiria rose is a hybrid which means seeds are not guaranteed to come true to the parent plant.

Osiria Rose Care

If you can find an Osiria rose for your garden, prepare to give it plenty of attention and care—you'll need to be patient with this flower. This is a slow-growing shrub with a long, repeat blooming period, but this rose does not exhibit hearty growth. One of the challenges is to bolster this plant's structure to support the large, showy but sparse flowers that often droop under their own weight.

• Hard to find
• High maintenance
• Requires extensive pruning and deadheading
• Vulnerable to pests, disease, and climate

Light

Plant Osiria rose in a full sun location that receives minimum six hours of direct light daily.

Soil

Organically rich, fertile soil is essential for successfully growing this rose. Work compost, aged manure, or other amendments in the soil before planting. A slightly acidic pH level of 6.0 to 6.5 is also important. If you are unsure about pH, have the soil tested and make necessary adjustments prior to planting. The soil must also have good drainage.

Water

Water when the top two inches of soil become dry. Generally, twice weekly is sufficient, however, higher temperatures and sandy soils create a need for more frequent irrigation. Water at the root zone and avoid wetting leaves, flowers and stems. A layer of mulch retains soil moisture and keeps the root zone cool.

Temperature and Humidity

Osiria rose grows and blooms best at 80 degrees Fahrenheit with relatively high levels of humidity. In colder growing zones with extended freezing temperatures, protect the plant with a thick layer of mulch. Locating it next to a building or stone structure improves winter survival.

Fertilizer

Feed Osiria rose in early spring at the start of the growing season and again in mid-summer. High phosphorous fertilizers support the large 4-inch blooms. Fertilizers listed for roses are a mix of nitrogen, phosphorous, and potassium—such as NPK 18-24-16. These fertilizers are formulated to meet their specific needs, but any fertilizer with a higher percentage of phosphorous supports healthy growth.

Types of Osiria Rose

The original Osiria rose was hybridized in 1978. Since then, other bi-color cultivars hybridized by crossing the tea rose with other rose hybrids, have appeared. These cultivars produce flowers in a range of colors beyond that of the original Osiria rose flower. Whether these cultivars are true Osiria roses is a subject of debate. For gardeners who want to add a bi-color rose to their garden, many rose growers recommend other, more reliable varieties that are easier to cultivate. Here are a few beautiful bi-color rose alternatives to consider.

• 'Fire N' Ice': A floribunda repeat bloomer, red with white reverse aging to violet-red. 4" lightly fragrant flowers.
  
• 'Love at First Sight': A hybrid tea rose featuring red flowers with a light pink reverse. This fragrant repeat bloomer is disease resistant.
• 'Rainbow Sunblaze': A small, mounding shrub rose to 2 feet tall with petite double blooms featuring tangerine petals tipped in cherry red with a yellow center. Adapts well to growing in pots.
• 'Chihuly': A floribunda type with double flowers patterned in shades of apricot, yellow, orange, and red. Mildly fragrant, 'Chihuly' grows to 3 feet tall and adapts well to pots.
• 'Life of the Party': Highly fragrant with soft yellow flowers edged in pink. This rose grows to 3 1/2 feet and is a continual bloomer with good disease resistance.
• 'Joseph's Coat': Grown as a climber or large shrub, 'Joseph's Coat' produces 4-inch semi-double blooms in shade of cherry-red, gold, and orange.

Pruning

Osira rose was created to provide cut flowers; not as a shrub rose designed for gardens. Weak stems are a drawback gardeners need to improve for this rose to show well. Pruning is done in late winter or early spring, cutting branches back to where they are no smaller than the diameter of a pencil. Remove branches in the center entirely to keep the shrub open for adequate air circulation and cut any dead branches back to the crown.

Using a sharp, sterile pruner, make an angled cut 1/4-inch above an outward-facing leaf. Pruning above an inward-facing leaf causes branches to cross and increases foliage in the plant's center. Deadhead spent flowers.

Propagating Osiria Rose

Osiria rose can be propagated with cuttings, but the challenge remains in finding a mature plant from which to take softwood stem cuttings. Take new growth stem cuttings after the plant has bloomed. Anytime throughout the season is okay but morning will give you cuttings with the best moisture level. The following tools and equipment are needed: sterile shears, rooting hormone, pot, sand and vermiculite mix, and plastic bag.

1. Use the shears to remove a green, new growth stem 8 inches or longer, making a 45-degree angled cut about 1/4-inch below a node
2. Split the stem below the node making an X-shaped cut with the shears or a sharp blade.
3. Remove bottom leaves keeping one set at the top of the stem.
4. Dip the stem bottom in a rooting hormone to cover the node.
5. Fill a pot with a moistened mixture of sand and vermiculite.
6. Use your finger or a pencil to create a narrow hole in the potting medium.
7. Lightly shake off excess rooting hormone and carefully insert that portion of the cutting into the hole.
8. Cover with a plastic bag. Poke a few small holes in the top of the plastic for ventilation or remove it for an hour or two every few days to provide ventilation. Use a small stake to keep plastic from contacting the top of the cutting, if needed.
9. Place the pot in a bright sunny location and keep the potting mix moist.
10. Roots form in one to two weeks. Check by gently tugging the cutting. Resistance indicates roots are established.

Tip

Rose cuttings have a low success rate for rooting. Improve your chances by placing several cuttings in a larger pot.

Overwintering

Osiria Rose thrives best in warm, dry climates, and needs protection from heavy rain, snow, and wind in growing zones 6 and lower. Protect the crown by covering it with soil and mulching around the base with a 3-inch layer of straw or wood chips. Remove excess soil in spring. Plant this rose in a location that receives plenty of sun but also provides protection from wind and stormy conditions.

Common Pests & Plant Diseases

Vulnerability to pests and diseases is an overriding concern for this delicate rose. Aphids, caterpillars, sawflies, leafhoppers, and spider mites are all attracted to Osiria rose. At the first sign of pests, try knocking them off with a strong spray from the garden hose. It may become necessary to treat your shrub with a high-quality pesticide spray. Rust, black spot, and powdery mildew are common problems to watch for. When caught early rust can sometimes be controlled by removing infected leaves. Treat black spot and powdery mildew with a recommended fungicide.

How to Get Osiria Rose to Bloom

Bloom Months

Osiria rose blooms in flushes from June until early fall depending on climate. It is not a heavy bloomer so flowers can be sparse.

How Long Does Osira Rose Bloom?

The shrub grows to maturity in three to five years and should bloom annually provided it receives adequate care. Even with the best care, disease and pest problems often lead to the early demise of the plant.

What Do Osiria Rose Flowers Look and Smell Like?

Flowers are noted for the distinctly sharp contrast between the insides and outsides of the petals. The insides feature shades of red to deep, dark hues of burgundy, wine, and magenta. Outside petals are stark white with some white occasionally appearing at the base of the inside petal.

Flowers have a velvety feel and a deep, musky rose fragrance.

How to Encourage More Blooms

Osiria has a reputation for being a stingy bloomer. Pruning for strong stems and structure along with special care given to watering, light, temperature, soil quality, and fertilization encompasses the best approach for achieving blooms.

Caring For Osiria Rose After It Blooms

After-bloom care involves a hard pruning in late winter or early spring. It's also important to keep the center of the shrub open by removing crossing branches and those that increase foliage in the center.

Deadheading Osiria Rose Flowers

Remove all spent and damaged blooms throughout the growing season, including those that droop and fail to open completely.

Common Problems With Osiria Rose

Yellowing Leaves

It's not uncommon for some older leaves to turn yellow and drop. If yellowing is widespread or occurs in young foliage several issues could be the cause. Overwatering is the first place to investigate. Make sure the soil is draining well and the base of the rose does not sit in standing water. Lack of sufficient light and incorrect soil pH can also cause yellowing foliage.

Curling Leaves

Fungal infections and infestation of sawflies cause leaves to curl. Treat the rose at the first sign of this problem with a fungicide or appropriate pesticide.

Drooping Flowers

Flowers droop on weak stems. This may be due to wind or other inclement weather damage. Expect to spend some effort improving the structure of Osiria rose through pruning and providing the extensive care requirements of this plant.

From: thespruce