Flower Colors Across the Seasons
- Chris Musser
- Oct 13
- 7 min read
When I began growing and studying PNW natives, I noticed patterns in the colors of flowers over the seasons. Spring starts out with white, yellow, and blue flowers, with one lone red flower and orange flower. In April, the colors become more intense, with lots of pinks and blues, and still some white flowers. May bloomers are more deeply colored still, purple, orange, and magenta dominate, and no white flowers. In June, even more intense pink, purple, orange, and golden yellow. Then in July, no more pink, but muted purples, yellows and brown. Clearly, there’s a pattern here. What’s it about?
Color in Ancient Plants
Before plants made flowers, they made colors for protection and survival. Only later, when flowering plants evolved, did plants’ use color shift from defense to communication.
Protection from Sunlight
Early plants lived in harsh sunlight, with lots of ultraviolet (UV) radiation. Pigments like carotenoids (orange/yellow) and anthocyanins (red/purple) acted as natural sunscreen, absorbing or scattering excess light. This protected chlorophyll from damage. You still see this today when young leaves emerge red or purple, a built-in shade until the chlorophyll matures.
Temperature Regulation
Darker pigments absorbed heat in cool environments; lighter or reflective surfaces kept tissues cooler in hot, exposed places. In mosses and lichens, red or brown pigments helped regulate temperature in alpine and tundra environments.
Stress Signals and Defense
Colors also evolved as stress responses. Red and purple anthocyanins often appear under drought, cold, or nutrient stress to protect cells by reducing oxidative damage. Some colors also deter herbivores by signaling toxicity or reducing palatability. For example, many ferns and liverworts turn reddish in sunlight not to attract anything, but to defend themselves from too much light or grazing.
Antioxidant & Anti-Pathogen Roles
Pigments such as flavonoids and tannins had antimicrobial properties long before pollination existed. These chemicals helped primitive plants resist fungi, bacteria, and viruses in humid environments.
Camouflage and Environmental Blending
In ancient ecosystems, certain pigments helped plants blend in or reflect background light in forests or rocky environments, reducing visibility to early herbivores.
What Insects Ate Before Flowers
Insects are far older than flowers, and for tens of millions of years, they thrived in a world without colorful petals or nectar.
Pollen and spores from ancient plants Conifers, cycads, and ferns produced plenty of tiny, nutrient-rich particles. Fossil evidence shows insects were already carrying pollen grains long before the first true flowers appeared.
Sap and leaves Many early insects chewed plant tissues or pierced stems to sip sap, much like aphids and cicadas do today.
Fungi Fungal mats and fruiting bodies were abundant, and some insects grazed on them the way beetles still do.
Dead stuff Detritus was a staple. Insects fed on decaying plant matter, dung, and other organic debris.
Other insects Predatory groups, like dragonfly ancestors, hunted their arthropod cousins in swampy Carboniferous forests.
When flowers arrived on the scene, they changed everything. Nectar was a brand-new, high-energy food source; pollen became easier to find and richer in protein. Plants, in turn, benefited from reliable pollination.
Color Through Different Eyes
Humans see a rainbow of red through violet, but other creatures see the world differently:
Bees can’t see red at all. To them, red is dull, almost black. Instead, their eyes are tuned to ultraviolet, blue, and green. Many ordinary flowers reveal dazzling UV nectar guides when viewed through a bee’s eyes.
Bumble bee sitting on a creeping zinnia in reflected ultraviolet photography using a UV filter. Photo by Dr. Klaus Schmitt Bumblebees have superior low-light sensitivity, and forage earlier and later in the day, and under cloud cover
Sweat bees prefer small yellow or white composite flowers, like fleabane, yarrow, asters
Mason and leafcutter bees have strong bias to blue and UV
Mining bees have keen UV vision that helps them locate pale or reflective spring flowers
Many native bees detect polarized light better than honeybees, giving them superior orientation in complex habitats like forest edges.
Flower-visiting flies also can’t see red; their vision peaks in UV, blue-green, and yellow-green.
Hoverfly photo by Charles Ray. Hoverflies are active on sunny days and are highly attracted to yellow, white and pale purple flowers.
Bee Flies feed on long-tubed flowers such as phacelia, penstemon, and clarkia. Females flick eggs into the nests of ground-nesting bees!
Tachinid Flies are frequent visitors of composite flowers, like yarrow, goldenrod, asters, feeding on nectar for energy.
Fungus Gnats pollinate small, pale, nodding flowers in bogs
Blow flies are attracted to carrion-scented and flesh-colored flowers, pollinating skunk cabbage, wild ginger, and trillium.
Butterflies have four color receptors, for UV, blue, green, and red/orange, and see a broader world of color than bees or flies, but not all butterflies see alike. Some are most sensitive to ultraviolet patterns, while monarchs and fritillaries can perceive fine distinctions in reds and violets.
Hummingbirds also have four color receptors in their eyes, including one tuned to red. Tubular red flowers, including red columbine, red flowering currant, scarlett beebalm, cardinal flower, California fuschia, scarlet gilia, firecracker penstemon are their preferred flowers.
Moths and bats do much of their work at night, when color doesn’t matter. They’re drawn to white and pale-yellow blooms that reflect moonlight and often give off a strong fragrance.
How plants fine-tune flower color
The paint itself: anthocyanins. Many flower colors—reds, purples, blues—come from a family of pigments called anthocyanins. Plants can tweak the exact shade by controlling how these pigments are made and where they go.
The “light switches”: transcription factors. Inside plant cells, certain proteins act like switches that turn pigment-making genes on or off. Depending on when and where these switches are active in a flower, the plant can change which pigments are produced. Example: One switch may be active only in petal tips, another in stripes—creating patterns.
Branching pathways Anthocyanins can be made in different “branches” of a chemical pathway, each leading to a slightly different pigment (more red, more blue, etc.). By redirecting chemical flow down one branch or another, plants shift the final hue.
After-effects (tweaks to the pigment itself):
pH of the cell sap shifts color toward red or blue.
Molecular stacking (pigments packing together in certain ways) deepens or changes hue.
Chemical decorations (like adding sugars or binding metals) change how pigments absorb light.
Surface effects Even if the pigment is the same, the structure of the petal surface can change how light reflects. Some petals have velvety textures, tiny ridges, or nanostructures that scatter light and create effects like iridescence (a shimmer, like on some tulips or hibiscus).
The Dance of Coevolution, Sunshine, and Place
The flower colors that move through the seasons are a living record of coevolution, adaptations not only to pollinators, but to sunlight, temperature, and place. Each hue reflects not just who pollinates a plant, but when and under what light it blooms.
In spring, soft light and cool temperatures favor pale yellows and blues: colors visible to bees emerging from hibernation. By summer, the sun is stronger and the cast of pollinators has changed: migrating butterflies and hummingbirds dominate, and the landscape answers in saturated oranges, pinks, and reds, pigments tough enough to withstand UV and heat.
Even within a single genus, geography and light shape color: Oregon’s pink Asclepias speciosa evolved under bright but dry western skies, balancing visibility for bees and butterflies with heat reflection, while the Midwest’s orange A. tuberosa glows hotter to match humid air, darker soils, and dense grasslands.
Pollinator Flowers by Color
Red (mainly hummingbirds, some butterflies):
Penstemon (P. barbatus)
Scarlet gilia (Ipomopsis aggregata)
Crocosmia (Lucifer)
Bee balm (Monarda didyma)
Salvias (Salvia microphylla, guaranitica)
Fuchsia
Orange (butterflies + hummingbirds):
Butterfly weed (Asclepias tuberosa)
Mexican sunflower (Tithonia rotundifolia)
Crocosmia cultivars (‘Emberglow’, ‘Emily McKenzie’)
Blanketflower (Gaillardia)
Nasturtium (Tropaeolum majus)
Zinnias (orange cultivars)
Yellow (bees + butterflies):
Oregon grape (Mahonia aquifolium)
Daffodils (Narcissus)
Sunflowers (Helianthus annuus)
Goldenrod (Solidago canadensis)
Evening primrose (Oenothera biennis)
Sedum ‘Autumn Joy’ (golden phase)
Blue (bees especially):
Camas (Camassia quamash)
Grape hyacinth (Muscari)
Lavender (Lavandula)
Salvia (S. guaranitica, deep blue cultivars)
Catmint (Nepeta)
Purple (bees + butterflies, some hummingbirds):
Asters (Symphyotrichum spp.)
Native clarkia (Clarkia amoena)
Lavender (Lavandula)
Penstemon (P. digitalis)
Salvias (purple types)
Echinacea (purple coneflower)
White/Cream (moths, bats, generalists):
Serviceberry (Amelanchier alnifolia)
Snowberry (Symphoricarpos albus)
Yucca
Nicotiana (ornamental tobacco, fragrant at night)
Evening primrose (Oenothera biennis)
Pollinator Flowers by Season
Spring (March–May):
Oregon grape (Mahonia aquifolium) – yellow, bees
Camas (Camassia quamash) – blue, bees
Serviceberry (Amelanchier alnifolia) – white, bees
Crocus, daffodils – yellow/purple, bees
Grape hyacinth (Muscari) – blue, bees
Early Summer (June–July):
Penstemon (P. barbatus) – red, hummingbirds
Native clarkia (Clarkia amoena) – pink/purple, bees + butterflies
Milkweed (Asclepias speciosa) – pink, butterflies
Lavender (Lavandula) – purple, bees
Blanketflower (Gaillardia) – orange/yellow, bees + butterflies
High Summer (July–August):
Scarlet gilia (Ipomopsis aggregata) – red, hummingbirds
Bee balm (Monarda didyma) – red, hummingbirds + butterflies
Crocosmia (Lucifer, orange cultivars) – red/orange, hummingbirds
Mexican sunflower (Tithonia rotundifolia) – orange, butterflies + hummingbirds
Zinnias (orange/pink) – butterflies
Sunflowers – yellow, bees
Late Summer–Fall (September–October):
Asters (Symphyotrichum spp.) – purple, bees + butterflies
Goldenrod (Solidago canadensis) – yellow, bees + butterflies
Sedum ‘Autumn Joy’ – pink/gold, bees
Salvias (S. microphylla, S. guaranitica) – red/purple, hummingbirds
Snowberry (Symphoricarpos albus) – white, bees
Night Bloomers (various months):
Evening primrose (Oenothera biennis) – yellow, moths
Nicotiana (ornamental tobacco) – white, moths
Yucca – white, yucca moths
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