Sunday, April 24, 2016

Botany for Hikers: Attracting Pollinators

I was setting up a shop to sell my photos on Etsy and, as I looked at my photos, a topic to discuss here came to me. If you just scroll through all of my photos, you see the same colors again and again. And for a minute it kind of bothered me. Was I doing something wrong? Perhaps I was accidentally only selecting flowers of just a few colors to photograph. Then it hit me. I was not the one who chose those colors. Pollinators were.

Unfortunately, even though I'd like flowers to grow in all shades of the rainbow to make my photos more interesting, the flowers have their own goal in mind. They are there for reproduction. Which means, as a flower lover, I am kind of a pervert for plant sex.

The difference between humans and plants is that we ladies have to attract men to inseminate us directly to get us pregnant, whereas plants need intermediaries. Imagine if men had to get a third party to take their semen and women had to convince that same third party to inseminate them with it. Instead of putting on low cut shirts that show cleavage to get the male flower parts to pollinate them, flowers need to attract pollinators to get the pollen from the male flower parts and deliver it to the female flower parts.

The male and female parts can be in the same flower, in different flowers on the same plant, or on different plants. Either way, all flowering plants have the same general option to get the job done: use wind for pollination, or convince an animal to do the job. Animals might be birds, bees, flies, bats, moths, butterflies, other insects, or even lemurs in one case.

Two major examples of wind pollination are corn and willows. They both seem to have the same strategy: produce a LOT of pollen and hope that some of it blows onto the pistils of a nearby stalk of corn or willow tree of the same species. In both cases, the plants feel no need to attract any animals at all. No need for brightly colored or fragrant flowers to attract pollinators, or a convenient landing pad where the pollinators can land.

On corn, the tassels have the male parts - just a lot of anthers covered in pollen - and the female parts are the silks coming out of the top of each ear of corn. Willow trees have a type of flowers called catkins, and most of us would not even call them "flowers" if we saw them, because they hardly resemble what you think of as a flower. Some willow catkins are all male, and some are all female. In both cases, you basically have collections of sex organs, all sitting around and hoping the wind will help it get lucky.

A female willow catkin. Just a big bunch of girl parts, waiting around for pollen to blow their way.

Now let's get on to the more colorful flowers.

If you see a flower that is RED, it might be trying to attract a bird.

Bush Monkeyflower

Flowers that attract birds tend to be:
  • Tubular and have petals that are recurved to be out of the way
  • Have tubes, funnels, cups
  • Strong supports for perching
  • Brightly colored: red, yellow, or orange
  • Odorless (birds have a poor sense of smell)
  • Open during the day
  • Prolific nectar producers with nectar deeply hidden
  • Modest pollen producers that are designed to dust the bird’s head/back with pollen as the bird forages for nectar

It's not a coincidence that those popular plastic hummingbird feeders are red.

Note that yellow and orange are listed above as colors that attract birds too. Yellow and orange flowers can also attract bees. But, unlike birds, bees can't see red! Then can see orange, yellow, blue, violet, and ultraviolet light.

Bee and Crocus
Nom nom nom


Bees like purple best, then blue. But they can see yellow and orange too. When I was looking at my photos, thinking I had screwed up because so many of my flower photos were yellow, white, and purple, that's what was going on. The flowers were just working hard to attract bees! Flowers can have landing platforms adapted for bees, scents to attract bees (or other pollinators they wish to attract), and even colored markings to guide the bees right to the food, kind of like the markings on a landing strip at an airport telling the plane where to go. Sometimes, those markings, called nectar guides, are UV so that bees can see them but humans can't.

Mountain Violet
Mountain Violet, on Mt. Laguna. The lines point to the bee food.

Baby Blue Eyes
Baby Blue Eyes, on Mt. Laguna, trying to look sexy to a bee.

Two other categories of pollinators are bats and flies. If you want to attract a bat, you don't need bright colors. Their color perception is not great. But you do need your flowers to open at night. And a strong fruity scent will help, or sometimes even a musty, rotten odor. Most bats eat insects, but bats that pollinate flowers eat nectar.

Flies also don't need fancy colors. Flowers that attract flies tend to be:
  • Pale and dull to dark brown or purple
  • Sometimes flecked with translucent patches
  • Putrid order, like rotting meat , carrion, dung, humus, sap and blood
  • Nectar guides not present
  • Produce pollen
  • Flowers are funnel like or complex traps

When I learned this subject in a botany class, the professor handed out a table with a row for each pollinator and columns that said what colors and odors and flower shapes they liked and a column that said what the pollinator gets from the flower. In most cases, the pollinators got nectar and/or pollen, but for flies it just said, "Nothing - flies get duped." Produce a nasty enough odor to attract a fly and you'll get your pollination for free.

For more information on the different types of pollinators out there, I recommend this site, where you'll find links for info on characteristics of plants pollinated by ants, butterflies, moths, wasps, beetles, and more.

Last, I'll leave you with my favorite pollination story of all. Hesperoyucca whipplei, also known as Chaparral Yucca or Our Lord's Candle is a common plant in Southern California.

Chaparral Yucca

Chaparral Yucca has a special relationship with its pollinator:

"It is pollinated by the California yucca moth (Tegeticula maculata), a relationship which has become a classic example of symbiosis. Working at night, the female yucca moth collects up to a dozen sacks of pollen grains called pollinia and forms them into a massive ball. She then flies to another plant and lands on the ovary of a flower. Standing with her head near the stigma, she inserts her ovipositor into the ovary wall and lays a single egg. She then rubs her pollen mass against the central stigmatic depression, ensuring pollination. The pollinated ovary will now produce many seeds, ensuring an ample food supply for the larva. Although many associations of Yucca and yucca moth exist, Tegeticula muculata and Hesperoyucca whipplei form an exclusive relationship."

Here's what I think is the coolest part. If the moth wanted to get lazy, she could simply lay all of her eggs in one flower and be done with the job. Her young would hatch and eat all of the seeds in that flower, and the flower would not get to reproduce at all. To the plant, that's not acceptable. So if a lazy moth lays all of her eggs in one flower, the plant kills off that flower, denying the moth larvae a food source. Instead, the moth has to do a lot of legwork to earn the right for her young to eat some of the plant's seeds. She lays only a few eggs in each flower, and has to visit many flowers, performing an awful lot of pollination for the yucca plant in the process. Then, when the seeds form and the moth larvae hatch, everyone gets some of what they want: the moth larvae eat some seeds, but not all of them, and the plant got pollinated for the price of a few seeds.

Next time you're on the trail and you see flowers in what feel like only a few colors, remember - it's not that nature is bad at decorating. It's the equivalent of going into a dance club and seeing all the girls in heels, tight pants, and low cut shirts and nobody wearing pajamas or turtlenecks.

Golden Evening Primroses
Flowers in Death Valley

Flowers on the PCT, just north of Agnew Meadows (near mile 915)

Flowers on the PCT, just north of Agnew Meadows (near mile 915)

1 comment:

  1. A really good writer brings her subject alive and you just did that with a real i don't want to say vengeance, I want to say genius, but that wouldn't be quite precise: About 80% of the way between talent and genius would be about right.
    Your photos are pretty nice, too.