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15 Flowers that Start with “O”

Orange Daylily flower

This is our list of flowers that start with "O". Each flower listed that starts with the letter "O" includes key information about how and where to grow it.

Below is our expansive gallery and directory featuring flowers that start with “O”.

One of my favorite flowers in this category is the Orange Daylily.

So-called because of its showy, trumpet-shaped tawny flowers, this perennial plant can grow from 6 inches to over 6 feet tall. It’s also called daylily because the flowers last for only a day. They bloom in the morning and die by nightfall.

Despite its short life span, the Orange Daylily has been dubbed as the “perfect perennial plant” because of its ability to survive all landscapes and climates. Native to the Eastern Asian countries China, Korea and Japan, the Orange Daylily is easy to grow, quick to multiply and an excellent colonizer. These flowers can be commonly spotted in alleys, old gardens, along roads and places with very poor soil.

Below is our entire gallery showcasing these flowers whose first letter is “O”.

Related: 100s of Flowers from A-Z

Obedient plant (Physostegia virginiana)

obedient plant_Physostegia virginiana

  • Common Name: Obedient plant
  • Scientific Name: Physostegia virginiana
  • Type: Perennial
  • Water: Medium
  • Soil PH: 5-7
  • Flower Color: Pink, white
  • Special Characteristics: Attracts hummingbirds, showy flowers, cut flowers, deer-resistant
  • Hardiness Zone(s): 3 to 9
  • Height At Maturity: 36-48″
  • Sun: Full sun
  • Sub Type: Groundcover

Obovate peony (Paeonia obovata)

obovate peony_Paeonia obovata

  • Common Name: Obovate peony
  • Scientific Name: Paeonia obovata
  • Type: Perennial
  • Water: Medium
  • Soil PH: 6.5-7.5
  • Flower Color: White, red, purple
  • Special Characteristics: Tolerates rabbit and deer, attracts butterflies, fragrant
  • Hardiness Zone(s): 5 to 8
  • Height At Maturity: 18-24”
  • Sun: Part shade
  • Sub Type: Groundcover

Ohio spiderwort (Tradescantia ohiensis)

Ohio spiderwort_Tradescantia ohiensis

  • Common Name: Ohio spiderwort
  • Scientific Name: Tradescantia ohiensis
  • Type: Perennial
  • Water: Dry to medium
  • Soil PH: 6.8-7.2
  • Flower Color: Deep blue to rose blue
  • Special Characteristics: Showy flowers
  • Hardiness Zone(s): 4 to 9
  • Height At Maturity: 24-36′
  • Sun: Full sun to part shade
  • Sub Type: Groundcover

Old Lady Cactus (Mammillaria Hahniana)

Mammillaria hahniana

  • Common Name: Old Lady Cactus
  • Scientific Name: Mammillaria Hahniana
  • Type: Cactus/Succulent
  • Water: Dry
  • Soil PH: 6.1 to 7.8
  • Flower Color: Pink
  • Special Characteristics: Container, Tolerates Drought
  • Hardiness Zone(s): 9 to 11
  • Height At Maturity: 1″ to 6″
  • Sun: Full Sun to Part Shade

Old Man of the Andes (Oreocereus Celsianus)

Oreocereus celsianus

  • Common Name: Old Man of the Andes
  • Scientific Name: Oreocereus Celsianus
  • Type: Cactus/Succulent
  • Water: Dry to Medium
  • Soil PH: 6.1 to 7.8
  • Flower Color: Pink
  • Special Characteristics: Container, Easy to Grow, Tolerates drought
  • Hardiness Zone(s): 8 to 10
  • Height At Maturity: 6″ to 120″
  • Sun: Full Sun to Part Shade

Old Man of the Mountain (Oreocereus Trollii)

Oreocereus trollii

  • Common Name: Old Man of the Mountain
  • Scientific Name: Oreocereus Trollii
  • Type: Cactus/Succulent
  • Water: Dry to Medium
  • Soil PH: 6.1 to 7.8
  • Special Characteristics: Attracts birds and Butterflies, Tolerates Drought
  • Hardiness Zone(s): 7 to 11
  • Height At Maturity: 12″ to 24″
  • Sun: Full Sun to Part Shade

Oleander Plant (Nerium Oleander)

Oleander Plant_Nerium-full sun

  • Common Name: Oleander Plant
  • Scientific Name: Nerium Oleander
  • Type: Shrub
  • Water: Moderate
  • Soil PH: 5 to 8.3
  • Flower Color: Pink, White
  • Special Characteristics: Poisonous, Showy Flowers
  • Hardiness Zone(s): 9-11
  • Height At Maturity: 96″ to 120″
  • Sun: Full Sun
  • Sub Type: Evergreen

Orange coneflower (Rudbeckia fulgida)

orange coneflower_Rudbeckia fulgida

  • Common Name: Orange coneflower
  • Scientific Name: Rudbeckia fulgida
  • Type: Perennial
  • Water: Dry to medium
  • Soil PH: 6-8
  • Flower Color: Orange / yellow
  • Special Characteristics: Attracts butterflies, deer-resistant, cut flowers, showy flowers, easy-to-grow
  • Hardiness Zone(s): 3 to 9
  • Height At Maturity: 24-36″
  • Sun: Full sun
  • Sub Type: Groundcover

Orange daylily (Hemerocallis fulva)

orange daylily_Hemerocallis fulva

  • Common Name: Orange daylily
  • Scientific Name: Hemerocallis fulva
  • Type: Perennial
  • Water: Medium
  • Soil PH: 6-7
  • Flower Color: Tawny orange
  • Special Characteristics: Attracts butterflies, tolerates rabbit, showy flowers, easy-to-grow
  • Hardiness Zone(s): 3 to 9
  • Height At Maturity: 24-30″
  • Sun: Full sun to part shade
  • Sub Type: Groundcover

Orange stonecrop (Sedum kamtschaticum)

orange stonecrop_Sedum kamtschaticum

  • Common Name: Orange stonecrop
  • Scientific Name: Sedum kamtschaticum
  • Type: Perennial
  • Water: Dry to medium
  • Soil PH: 6.8 – 7.2
  • Flower Color: Yellow
  • Special Characteristics: Attracts butterflies, deer-resistant, tolerates rabbit, showy flowers, easy-to-grow
  • Hardiness Zone(s): 3 to 8
  • Height At Maturity: 3-6′
  • Sun: Full sun
  • Sub Type: Groundcover

Oregano (Origanum vulgare)

oregano_Origanum vulgare

  • Common Name: Oregano
  • Scientific Name: Origanum vulgare
  • Type: Perennial
  • Water: Dry to medium
  • Soil PH: 6-8
  • Flower Color: Pinkish-purple or white
  • Special Characteristics: Attracts butterflies, deer-resistant, fragrant, showy flowers, easy-to-grow
  • Hardiness Zone(s): 4 to 8
  • Height At Maturity: 6-36′
  • Sun: Full sun
  • Sub Type: Groundcover

Oregon Grape (Mahonia)

Grape Holly_Mahonia-part shade to full shade

  • Common Name: Oregon Grape
  • Scientific Name: Mahonia
  • Type: Shrub
  • Water: Needs moderate moisture
  • Soil PH: 7.6-7.8
  • Flower Color: Yellow
  • Special Characteristics: Deer-resistant
  • Hardiness Zone(s): 5-9
  • Height At Maturity: 48-96″
  • Sun: Full Sun, Partial shade
  • Sub Type: Deciduous

Organ Pipe Cactus (Stenocereus Thurberi)

Stenocereus thurberi

  • Common Name: Organ Pipe Cactus
  • Scientific Name: Stenocereus Thurberi
  • Type: Cactus/Succulent
  • Water: Dry
  • Soil PH: 6.1 to 7.8
  • Special Characteristics: Tolerates Drought
  • Hardiness Zone(s): 9 to 11
  • Height At Maturity: 72″ to 144″
  • Sun: Full Sun

Orienpet Lily (Lilium Silk Road)

Orienpet-Lily_Lilium'SilkRoad'

  • Common Name: Orienpet Lily
  • Scientific Name: Lilium Silk Road
  • Type: Perennial
  • Water: Medium
  • Soil PH: 5.5 to 6.5
  • Flower Color: Pink
  • Special Characteristics: Attracts birds and butterflies, Cut flowers, Fragrant
  • Hardiness Zone(s): 5-9
  • Height At Maturity: 4″-6″
  • Sun: Full Sun
  • Sub Type: Groundcover

Ox eye (Heliopsis helianthoides var. scabra)

ox eye_Heliopsis helianthoides var. scabra

  • Common Name: Ox eye
  • Scientific Name: Heliopsis helianthoides var. scabra
  • Type: Perennial
  • Water: Dry to medium
  • Soil PH: 6-8
  • Flower Color: Yellow orange rays and brownish yellow center
  • Special Characteristics: Attracts butterflies, cut flowers, showy flowers, easy-to-grow
  • Hardiness Zone(s): 3 to 9
  • Height At Maturity: 36-48″
  • Sun: Full sun
  • Sub Type: Groundcover

Ox-eye daisy (Heliopsis “Helhan” LORAINE SUNSHINE)

ox-eye daisy_Heliopsis 'Helhan' LORAINE SUNSHINE

  • Common Name: Ox-eye daisy
  • Scientific Name: Heliopsis “Helhan” LORAINE SUNSHINE
  • Type: Perennial
  • Water: Dry to medium
  • Soil PH: 5.8 – 6.2
  • Flower Color: Yellow
  • Special Characteristics: Attracts butterflies, cut flowers, showy flowers, easy-to-grow
  • Hardiness Zone(s): 3 to 9
  • Height At Maturity: 24-30″
  • Sun: Full sun
  • Sub Type: Groundcover

Ox-eye sunflower (Heliopsis helianthoides)

oxeye sunflower_Heliopsis helianthoides

  • Common Name: Ox-eye sunflower
  • Scientific Name: Heliopsis helianthoides
  • Type: Perennial
  • Water: Dry to medium
  • Soil PH: 5.5 to 7
  • Flower Color: Orange-yellow rays with brown center disks
  • Special Characteristics: Attracts butterflies, cut flowers, showy flowers, easy-to-grow
  • Hardiness Zone(s): 3 to 9
  • Height At Maturity: 36-72″
  • Sun: Full sun
  • Sub Type: Groundcover

The Orange Daylily appears in Chinese cuisine because of its edible and nutritious roots and flowers. It is believed that eating the flowers can help detoxify and even cure insomnia. Another belief surrounding the Orange Daylily is that pregnant women wearing these flowers on their waist will give birth to a male child.

Know more about the perennial flower Orange Daylily plus all other interesting plants and flowers that start with “O.”

Not a lot of websites thoroughly list plants and flowers alphabetically. However, because we have a database set up, we’re able to offer a comprehensive listing of plants and flowers that you can filter alphabetically.

Be sure to also check out our entire garden directory where you’ll find annuals as well.

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