16 Flowers That Begin With O

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Perhaps you’re an experienced green thumb or a new gardener looking to spruce up your space, but without a doubt, you’ve discovered that choosing what flowering plants to include in your garden is no easy feat! Wrapping your head around perennials, annuals, shrubs, trees, bushes, and more, may seem like a headache, but with some key information and a little planning, your dream landscape is easy to achieve! 

This short list of different flowers that start with the letter O should be able to narrow down the selection for you and provide you with the information you need at a glance to know if the plant is the right fit. Just remember that many tender perennials can be grown as annuals in colder climates, so if you live somewhere cold but have your heart set on a tropical flower, all is not lost!  

#1 Obedient Plant

The obedient plant, Physostegia virginiana, or the false dragon head is a herbaceous perennial that can grow in USDA zones 2-9.  These flowers are native to Eastern North America and North Carolina and have a tremendous value to wildlife. Plant them in pollinator gardens to attract bees, butterflies, and hummingbirds. 

Obedient plants have a long blooming season from July to October, with showy flower spikes adorned with white, pink, or purple flowers that are smaller than 1 inch across. Grow these versatile plants in full sun to partial shade in a meadow, naturalized, cottage-style, or woodland garden! They prefer moist soil making them suitable for planting along pond edges.  

#2 Obovate Peony

Paeonia obovata or the obovate peony is an easy-to-grow herbaceous perennial with a height and spread of 2 feet. They can be found growing wild in eastern temperate Asia and bloom in May for a mere 7-10 days each year! Their mildly fragrant flowers are single, cup-shaped, and grow as wide as 3 inches across. Flowers can be white to rose-purple and have golden-yellow stamens. 

This compact peony species are well-suited for shade or open woodland gardens with foliage that remains attractive past the blooming season. They will require some light maintenance coming up to winter and will need to be cut back down to the ground in the fall before the first frost. 

#3 Ohio Spiderwort

This wonderful perennial wildflower can be found growing in meadows, woodland margins, and along roadsides in eastern and central North America. They have a tremendous wildlife value in their native range, attracting bees, butterflies, and even acting as a larval host! These plants are known as the Ohio spiderwort, blue jacket, or the smooth spiderwort, and their Latin name is Tradescantia ohiensis

Their lovely flowers have 3 petals, are purple to pinkish-blue, and only bloom for a single day. Plant them in full sun conditions for the best results, as while they will tolerate partial shade, they won’t perform as well. They bloom from spring to summer but can be encouraged for a second fall bloom if cut down to 6-12 inches in mid-summer. Ohio spiderworts look incredible when planted en masse in meadow gardens, along walkways, or in patio gardens!

#4 Orange Coneflower

Rudbeckia fulgida or the orange coneflower is a perennial plant belonging to the daisy family, Asteraceae, and is native to southeastern North America. They grow best in organically rich soils under full sun conditions, although they can withstand some light shade! They have a long blooming season from June to October and can be deadheaded to encourage additional blooming.  

Orange coneflowers are clump-forming, growing to a maximum height of 3 feet, and are prolific bloomers! They have daisy-like flowers that grow as wide as 2.5 inches, with yellow rays and purplish-brown central disks. Plant them in sweeping drifts along cottage-garden borders, meadow gardens, or even pollinator gardens, as their flowers are attractive to butterflies and their seeds are eaten by birds!  

#5 Orange Daylily

The orange daylily, Hemerocallis fulva, is named after its bold 5-inch wide, orange lily flowers. They are clump-forming and spread rapidly via rhizomes forming dense patches. Orange daylilies are originally from China and Japan but have become widely naturalized in parts of the US. These bold bulbous perennials can grow to a stunning 6 feet high and are relatively low-maintenance.

Plant them in full sun to partial shade, in soils high in organic matter with good drainage. Orange daylily flowers are well suited for pollinator, edible, and drought-tolerant gardens, making them extremely versatile! Their flowers and buds are edible with a peppery, sweet, and spicy flavor, however, they are poisonous to felines so care should be taken.     

#6 Orange Star

This fantastic bulbous perennial goes by the names orange star, sun star, star of Bethlehem, and Ornithogalum dubium. It has a long blooming season from winter to spring producing incredible clusters of 5-25 vivid yellow to orange flowers with a contrasting black central eye. They are low-growing reaching between 8 and 12 inches tall making them great for growing in containers, window boxes, or at the front of borders!

Orange stars are native to South Africa and will grow best under full sun and in well-drained soils. They have average water needs making them good candidates for gravel and rock gardens. Their beautiful flowers are great as cut flowers which are perfect for brightening up the home during the colder months.  

#7 Orange Stonecrop

Phedimum kamtschaticus, previously known as Sedum kamtschaticus, goes by the common name orange stonecrop. It is a herbaceous perennial found growing naturally in forests and natural areas of Russia and Eastern Asia. Orange stonecrops are popular as houseplants, however, orange stonecrops are also useful as ground cover outdoors. 

Plant them in full sun and very dry soils in USDA zones 3-6. They are spring bloomers with 4-5-petaled, orange-yellow flowers that grow in flat clusters. Orange stonecrops are attractive to pollinators so are a top choice for pollinator gardens!   

#8 Orchid

Orchids belong to the family Orchidaceae and are any of the 25,000 species and 1,000 genera found worldwide throughout the world, particularly in the wet tropics. They are known for their extremely attractive flowers and are generally terrestrial or epiphytic perennial plants. Most species in this large group make their own food, however, some live on dead organic matter, or get their nutrients from a fungus that lives on their roots. 

Orchid flowers range in size from extremely small (0.1 inches) to extremely large species that have flowers that can grow up to 15 inches wide! Orchids are extremely popular house plants and are popular in the florist industry for their exotic flowers, but they are also important commercially in the production of vanilla which is primarily derived from the species Vanilla planifolia

#9 Oriental Lily

Oriental lilies are a group of hybrid lilies that are usually the last of the lilies to bloom. The most well-known oriental lily is the stargazer which is famed for its long-lasting, fragrant flowers making it extremely popular in the florist industry! Members of this group are prized for their flamboyant colors and large, showy flowers. 

They have a long blooming period from mid to late summer, or even fall for some types! Their striking flowers come in bold shades of white, pink, and red, some of which have attractive yellow bands across their petals and spotted throats. Oriental lilies may die in alkaline soils, so in gardens with high levels of alkalinity, they should be grown in containers. 

#10 Oriental Poppy

The oriental poppy or Papaver orientale is a huge favorite within the poppy family! These perennials grace the garden from late spring to early summer with bold, eye-catching flowers. They are clump-forming, reaching 2-3 feet high with silvery-green foliage and 4-6 inch wide satin-silk flowers! There are plenty of incredible oriental poppy varieties that come in a range of rich flower colors like white, pink, red, and orange. 

These delightful flowers are a fantastic choice for beds and borders in cottage-style or rock gardens. However, oriental poppies go dormant and die down after flowering so should be planted alongside flowers that grow later in the year such as baby’s breath or Russian sage, to fill in the gaps they leave behind!

#11 Ornamental Ginger

Ornamental gingers are a diverse group that are staples of any tropical garden! They are tender perennials that grow best on rich, moist soil, either in sun or shade. They reproduce underground through rhizomes and many go dormant in cooler climates to return once the weather gets warmer. Ornamental gingers are typically low-maintenance with pretty glossy green foliage and striking flowers and bracts. 

One of the most popular ornamental gingers is Etlingera elatior or torch ginger. It is winter hardy to USDA zones 10-12 and is native to Thailand, Malesia, and New Guinea. They can grow to a height of 15 feet and have flower stalks that can reach 3 feet tall topped with a striking cone consisting of red bracts and tiny yellow flowers. 

#12 Oxblood Lily

Rhodophiala bifida also called the oxblood lily is a bulbous perennial native to Brazil and Argentina. They grow well in containers making them a great choice for patio and container gardens. Plant them in full sun to partial shade facing south, east, or west in cooler climates. 

Oxblood lilies grow between 10 and 16 inches high and will bloom over summer or early fall, producing pretty umbels of narrow, funnel-shaped flowers in groups of up to 5 flowers. Blooms are rich, deep, red that contrasts nicely against its green foliage. 

#13 Ox-eye Daisy

The ox-eye daisy or Leucanthemum vulgare is a herbaceous perennial in the daisy family Asteraceae. They are popular garden flowers that are native to Asia and Europe but have become widely naturalized in the US. They grow as tall as 2-3 feet, producing numerous daisy-like flowers that are 1-2 inches wide. 

Ox-eye daisies bloom all summer long, and their flowers have white outer rays and yellow central discs. These low-maintenance plants are well-loved for wildflower or meadow gardens and make excellent additions to pollinator gardens as they are known for attracting bees, insects, butterflies, moths, and birds into the garden!

#14 Ox-eye Sunflowers

Heliopsis helianthoides also known as the ox-eye sunflower belongs to the daisy family Asteraceae and is native to central and eastern North America. They bloom from June to August with a final height typically between 3 and 4 feet and a final spread of up to 4 feet! Ox-eye daisies are extremely low-maintenance, do well in full sun, and are drought tolerant.

Plant these flowers along perennial borders for a bright splash of color or grow them in prairie or naturalized gardens. Their daisy-like flowers grow as wide as 2-3 inches with sunshine yellow outer rays and yellow-orange centers!

#15 Oxlips

These delightful plants are easy to grow and are extremely popular for cottage-style, woodland, meadow, and prairie garden beds, and borders! Oxlips are also called Primula elatior, great cowslip, and true oxlip and are native to southwestern Asia and Europe. They do well in partial shade and should be grown in average, well-drained soils. 

Oxlips flowers bloom from mid-spring to early summer with dainty flower clusters that rise above their foliage from leafless stalks. Flowers are soft buttery yellow with a darker center. These nodding flowers are delightfully fragrant and grow up to 1 inch across. They look particularly stunning when planted in large groups! 

#16 Oyster Plant

Tradescantia spathacea, also known as the oyster plant, Moses-in-the-cradle, and the boat lily, is a tender perennial that will need overwintering indoors in colder climates. Oyster plants are prized more for their beautiful foliage than their modest flowers, which are less than 1 inch across, white, and appear inside a pair of waxy purple bracts or “boat” nestled in the foliage!

These striking tropical plants are native to southern Mexico and Guatemala, and are low growing only reaching a maximum height of 1 foot high, making them ideal for year-round ground cover and path edging in warmer climates! They have attractive lance-shaped leaves that can be green with deep purple undersides, or variegated with cream and green stripes and a lavender underside.