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10 Outstanding Flowers that Start with O

Make your garden even more eye-catching by adding some of these outstanding flowering plants. Whether you’re striving to improve curb appeal or to design the perfect outdoor oasis, you’re sure to find something of interest on this list of 10 flowers that start with O.

Ornithogalum - Star of Bethlehem flowers

Annual Flowers that Start with O

1. Ocean pearls (Agrostemma githago)

ocean pearls

Also called white corn cockle, the elegant flowers of ocean pearls bloom on gray, willowy stems in the summer. Golden stitching appears to work outward from the base of each ivory petal. These old-fashioned cottage garden plants often self-sow and are also excellent cut flowers.

Although they tolerate most soil types, ocean pearls perform best in well-draining soil and full sun.

2. Orlaya (Orlaya grandiflora)

orlaya flowers

This hardy annual produces an abundance of large, flat, white flowers from early summer until the first frost. Although closely resembling Queen Ann’s lace, this well-mannered cousin is less invasive. Orlaya has a compact habit and requires little care, growing well in beds, borders, cottage gardens, and cutting gardens. It also attracts pollinators and repels deer.

Plant orlaya in average to rich, well-draining soil in a location that receives full sun to light shade.

3. Osteospermum (Dimorphotheca ecklonis)

Osteospermum flowers

The bright daisylike blossoms of osteospermum bloom in the spring and fall in cheery shades of purple, pink, white, yellow, or orange, often with bluish-purple centers. Some varieties even feature unique spoon-shaped petals. Osteospermum grows well both in containers and in the ground, and its flowers are a fun addition to fresh bouquets.

The more sunlight osteospermum receives, the better it blooms, and it should be planted in evenly moist, well-draining soil.

Perennial Flowers that Start with O

4. Obedient plant (Physostegia sp.)

Obedient plant

Don’t be fooled by the well-mannered name of this North American wildflower, which is called obedient plant for the unique trait of flowers that stay in place when pushed or twisted around the stem. The plant itself, on the other hand, goes where it pleases through underground runners. Planting it in a pot or well-contained bed will help keep it from spreading. The lovely spires of pinkish snapdragon-like blossoms grant obedient plant another name: false dragonhead.

Obedient plant prefers full sun and rich, moist, well-draining soil; planting it in drier soil may help slow its spread.

5. Oriental lily (Lilium orientalis)

Oriental lilies

This tall, fragrant lily blooms late in the season, usually starting around August. It can grow up to six feet high, depending on the cultivar, and produces large, open blossoms. The flowers come in shades of white, pink, and red, often with striking patterns on the petals, and are a favorite among florists.

Plant lilies in full sun and soil with excellent drainage, as they do not tolerate wet conditions.

6. Oriental poppy (Papaver orientale)

oriental poppies

Although available in a variety of colors, oriental poppies typically come in the popular vibrant red-orange hue. They bloom in late spring to early summer, go dormant during the hottest period, then produce new growth in the fall that lasts through the winter.

Plant oriental poppies in well-draining soil in a location that receives at least six hours of sunlight each day.

7. Ornamental onion (Allium sp.)

ornamental onions

Also known by their genus, allium, ornamental onions bloom in the late spring or early summer. Their showy globes of flowers, in shades of pink, purple, blue, white, or yellow, balance on long, slender stalks. Ornamental onions attract pollinators yet repel deer and other mammal pests, and they make excellent cut flowers.

Although they tolerate partial shade, ornamental onions prefer full sun, and they should be planted in well-draining soil.

8. Ornamental oregano (Origanum laevigatum)

Ornamental oregano

Although oregano is most often used as a kitchen herb, this ornamental species produces abundant clusters of pink blossoms that attract butterflies and other pollinators like a magnet. Depending on the variety, these attractive spreading plants reach about two feet tall.

Oregano grows best in full sun and well-draining soil and is often drought tolerant once established.

9. Ornithogalum (Ornithogalum sp.)

Ornithogalum flowers

Also aptly called star of Bethlehem, ornithogalum produces delicate, starry white blooms with six petals fanned around six stamens. It spreads readily and tolerates partial shade, making it an excellent groundcover in woodland gardens. Small bulbs surrounding the “mother” plant can be removed to reduce spreading or to transplant elsewhere.

Plant ornithogalum bulbs in rich, moist, well-draining soil in full sun to light shade.

10. Oxeye daisy (Leucanthemum vulgare)

Oxeye daisy flowers

This classic daisy features white petals surrounding a sunny yellow center. A European native, oxeye daisy unfortunately can be invasive in North America, so check with your local extension office before planting or choose native alternatives instead: daisy fleabane, flat-topped aster, and heath aster, all look similar, as does the hybrid Shasta daisy.

Oxeye daisies tend to grow in open, disturbed areas like roadsides and ditches.

From attractive front lawns to secret backyard gardens, any space can benefit from one or more of these outstanding flowering plants that start with O. Happy growing!

Outstanding flowers that start with O
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Serena Manickam is a freelance editor and writer and sustainable market gardener in rural Virginia. She holds a BA in environmental science and runs Fairydiddle Farm, a small market garden in which she grows no-spray produce and herbs to sell at a local farmer’s market.

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