25 Flowers That Start With R (Names, Bloom Times & Toxicity)

Flowers that start with R are dominated by one genus above all others — the rose — but the letter also covers rhododendrons, rudbeckia, ranunculus and a carnivorous bog plant that catches its own insects. Three of them carry genuine hazards, including one that burns skin in sunlight.

This guide covers 25 flowers beginning with R, with botanical names, plant type, bloom season and what makes each distinct. Toxic and irritant species are flagged.

Flowers Starting With R: Quick Reference

Roses and Rose Relatives

Rose

The most cultivated ornamental flower in the world, with tens of thousands of named varieties. A point of pedantry that is actually useful: roses do not have thorns. They have prickles — outgrowths of the outer stem layer that snap off cleanly — whereas true thorns are modified branches with vascular tissue running through them. Roses also produce hips, which are among the richest common sources of vitamin C, though the irritant hairs inside must be removed before use.

Rose of Sharon

Hibiscus syriacus, a hardy deciduous shrub flowering from midsummer into autumn when most shrubs have long finished. Confusingly the same common name is applied to Hypericum calycinum in Britain, a low yellow-flowered ground cover, and to a different plant again in North America. Check the botanical name when buying.

Rose Mallow

Hibiscus moscheutos is a hardy perennial hibiscus producing flowers up to 30 cm across — the largest of any plant that survives a cold winter. It dies to the ground each year and emerges very late in spring, which regularly convinces gardeners it has died.

Rose Campion

Lychnis coronaria sets vivid magenta flowers against silver-felted foliage, a combination few plants manage. It is a short-lived biennial that self-seeds reliably, so a colony persists even though individual plants do not.

Rockrose

Each rockrose flower lasts a single day, its crumpled petals dropping by afternoon — but a healthy plant opens so many in succession that the display runs for weeks. They demand full sun and sharp drainage, and resent both rich soil and being moved once established.

Border and Meadow Plants

Rudbeckia

Black-eyed Susan and its relatives, prairie natives that flower from midsummer well into autumn. The dark central cone is a mass of disc florets. Leave the seedheads standing over winter rather than deadheading late — goldfinches strip them, and the blackened cones hold their shape under frost.

Red Hot Poker

Kniphofia sends up torch-like spikes that open from the bottom upward, so a single stem carries red buds above and yellow open flowers below — the source of the two-tone effect. In its South African habitat it is pollinated by sunbirds, and in gardens it is worked heavily by bees. It wants sharp drainage; wet winter soil kills it faster than cold.

Red Valerian

Centranthus ruber colonises walls, cliffs and rubble, thriving in almost no soil at all. Its long-spurred flowers suit butterflies and hawkmoths particularly well. It seeds prolifically and has naturalised far beyond its Mediterranean origin, becoming invasive in parts of North America and Australia.

Russian Sage

Hazy blue-violet spires above aromatic silver foliage in late summer, holding up in drought and heat better than almost anything else in a border. Despite the name it is neither Russian nor a true sage, and it was reclassified from Perovskia into Salvia in 2017.

Ragged Robin

Silene flos-cuculi takes its name from petals so deeply cut they look torn. It is a plant of damp meadow and marsh, and it has declined sharply across Europe as wet grassland has been drained — making it a useful indicator of surviving habitat.

Restharrow

Ononis repens earned its name honestly: its tough, wiry, deep roots were substantial enough to stop a harrow being dragged through a field. It produces small pink pea flowers and fixes nitrogen, and it tolerates poor, chalky, coastal ground.

Rue Anemone

Thalictrum thalictroides is a delicate woodland ephemeral flowering in early spring before the tree canopy closes. What look like white petals are actually sepals — the plant has no true petals at all — and the foliage resembles rue, which gives it the name.

Bulbs, Rock Plants and Curiosities

Rain Lily

Zephyranthes does what the name says: bulbs sit dormant through dry weather and flower in a sudden flush a few days after heavy rain, often across a whole population at once. The trigger appears to be the drop in soil temperature that accompanies a soaking rather than the water itself.

Round-leaved Sundew

Drosera rotundifolia is carnivorous, growing in acidic bogs so nutrient-poor that it supplements its nitrogen by catching insects. Each leaf carries tentacles tipped with sticky droplets that look like dew and never dry; when prey sticks, the tentacles slowly curl inward and the leaf digests it. It is protected in many regions and should never be dug from the wild.

Rockfoil

Saxifraga means “stone-breaker,” from its habit of rooting into rock crevices — and from an old doctrine-of-signatures belief that it could therefore break kidney stones. It forms tight cushions and needs excellent drainage, dying quickly in wet or heavy soil.

Rock Cress

Arabis spreads into mats topped with white or pink cross-shaped flowers each spring. Like aubrieta and candytuft it must be sheared back after flowering or it goes woody and bare in the centre within a couple of seasons.

Rhodanthe

An Australian paper daisy whose bracts are dry and papery even on the living plant, so cut stems dry with almost no change in colour or shape. It needs heat, full sun and sharp drainage, and dislikes humidity.

Roman Chamomile

Chamaemelum nobile smells distinctly of apple when crushed. The non-flowering cultivar ‘Treneague’ is the one used for chamomile lawns and seats — it stays low and releases scent when walked on, though it will not take the traffic a grass lawn tolerates.

Rocket

Dame’s rocket, Hesperis matronalis, releases its scent in the evening rather than by day. It is often mistaken for phlox; the reliable tell is petal count — rocket has four, phlox has five. It is invasive across much of North America and should not be introduced deliberately.

The Hazardous Ones

Rue

Ruta graveolens has striking blue-grey foliage and a long history as a medicinal and strewing herb. It is also the most genuinely dangerous plant to handle on this list — not to eat, but to touch.

Rhododendron

Spectacular spring shrubs demanding acid soil — in alkaline ground the leaves yellow between the veins as iron becomes unavailable. Azaleas belong to the same genus.

Ranunculus and Rocket Larkspur

Persian buttercup (Ranunculus asiaticus) produces tightly packed, almost paper-layered blooms prized as cut flowers. Rocket larkspur (Consolida ajacis) sends up tall spires closely related to delphinium.

Growing Notes

Sharp drainage essential: red hot poker, rockrose, rockfoil, rock cress, Russian sage and rhodanthe — wet winter soil kills all of them faster than cold does. Acid soil required: rhododendron. Damp ground: ragged robin, rose mallow and round-leaved sundew. Late-season colour: rose of Sharon, rose mallow, Russian sage and rudbeckia all peak when most shrubs and perennials have finished.

Two emerge very late in spring and are routinely dug up as dead — rose mallow and Russian sage. Give them until early summer before giving up.

Frequently Asked Questions

What flowers start with the letter R?

Twenty-five are covered here, including rose, rhododendron, rudbeckia, ranunculus, rosemary, red hot poker, Russian sage, red valerian, rose of Sharon, rose mallow, rose campion, rockrose, rock cress, rockfoil, rain lily, ragged robin, restharrow, rocket larkspur, rocket, Roman chamomile, rhodanthe, rocktrumpet, rue, rue anemone and round-leaved sundew.

Do roses have thorns?

Not technically. Roses have prickles — outgrowths of the stem’s outer layer that snap off cleanly. True thorns are modified branches with vascular tissue running through them, as on hawthorn or blackthorn. The distinction is real botanically even though everyone says thorns.

Which R flower is most dangerous?

Rue, but by contact rather than ingestion. Its sap contains furanocoumarins that react with sunlight to cause severe blistering burns which can take weeks to heal. Rhododendron is the most dangerous to eat, containing grayanotoxins that affect heart rhythm.

Why are my rhododendron leaves turning yellow?

Almost always soil pH. Rhododendrons need acid soil, and in alkaline ground they cannot take up iron, so leaves yellow between the veins while the veins stay green. Feeding will not fix it permanently — either grow them in ericaceous compost in containers or choose a different shrub.

Is rosemary still called Rosmarinus?

No. Rosemary was reclassified in 2017 and is now Salvia rosmarinus, placing it within the sage genus. Many nurseries and books still use the old name Rosmarinus officinalis, so you will see both.

What makes rain lilies flower?

Heavy rain, with a delay of a few days. A whole population often flowers simultaneously after a soaking. The trigger appears to be the drop in soil temperature accompanying the rain rather than moisture alone.

Sources

Furanocoumarins and phytophotodermatitis from Ruta graveolens: dermatology and clinical toxicology literature. Grayanotoxins and mad honey poisoning: peer-reviewed toxicology literature. Ranunculin and protoanemonin, and diterpene alkaloids in Consolida/Delphinium: standard toxicological plant references. Rosmarinus to Salvia reclassification: current botanical nomenclature.

This article is for general information. Never eat any flower or plant part unless you are certain of its identification, and wear gloves when handling rue — several plants listed here are toxic or cause skin injury.

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