Yes, though the yes is a small one. Red sits right at the edge of what a bee can tell apart from the green of a leaf. A bee crossing your garden picks up almost no color signal off a red petal. Most of the muddle around bee vision red flowers goes back to one textbook line, the one saying bees cannot see red at all. That line is too strong. Bumblebees can sort red reflectance patterns from other patterns, and a few red flowers depend on bees to set seed.
Picture one red bloom in your border and two visitors to it. A hummingbird gets a loud signal against the foliage and can pick your flower out well before landing. A bee gets a faint smudge of difference and leans on scent and on memory of yesterday's route. Both visitors reach your flower and work it. You are watching two different jobs, and that gap is the whole story here.
Can bees see red? Yes, and the size of that yes has been measured. Color difference between a flower and the leaves behind it gets a number. That number comes in just-noticeable differences, or JNDs. One JND is the smallest color gap an eye can register at all. Below that gap, two shades look like one shade to you. Chen and colleagues, writing in Annals of Botany in 2020, put the mean contrast of red flowers at 1.07 JNDs for bees. Birds looking at those same flowers got more than 10 JNDs.
A value that sits a hair above threshold is an odd thing to work with. A bee can register that something has changed. The change is nowhere near strong enough to pull that bee in from across your yard. A bird facing the same petal has close to ten times the contrast to go on, which is why you keep seeing red on flowers built around birds.
The counter-evidence is real, so here you go. Of 130 red-flowered species sampled across 104 genera and 53 families, 10, or 7.7%, were bee-pollinated. Red is not a bee-proof color. Those bee pollinated red flowers share a tendency. As a group they carry a higher secondary peak in the blue and ultraviolet range. Blue and ultraviolet sit where a bee eye works best.
That second peak matters more to a bee than the red does. A petal can look deep red to you and still throw off a bounce of blue and ultraviolet light. Bees have no red photoreceptor to work with. What a bee does have covers the range where that second peak lands. The red is close to noise. That bounce coming off your petal is signal.
Bird-pollinated red flowers run the other way. Those secondary peaks are low or gone. The authors matched flower spectra against pollinator groups. Animals with no red photoreceptor lined up with the high-peak flowers, and birds lined up with the low ones, at P = 0.005. A result that strong is unlikely to have come out of the sampling by chance.
The reading of that pattern is the part worth sitting with. The authors took the shift toward low secondary peak red as driven more by avoiding bees than by attracting birds. A deep red petal with no blue or ultraviolet bounce works less as an ad aimed at birds. It works more as a way of going quiet on bees.
So keep the careful wording and drop the textbook line. Red is much less conspicuous to bees, never invisible to them. A red flower in your border will still get visits, and a bee that learns where you planted it comes back. Red just never calls to a bee across your yard the way blue and purple do.
Read the full article: 10 Red Flowers and What Makes Them Red
