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”.

Table of Contents Show

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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.