26 June 2010

Why hummingbirds like red flowers (hint: actually, they don't.)

I'd been meaning to write this post for a while, and then I realized: It is National Pollinator Week!  So I didn't really write this specifically for the week, but hey, it is all about pollinators, so I'll go with it.

The hummingbirds are back, zipping around my garden, sipping nectar from their preferred plants. Imagine for a moment the flowers the hummingbirds are visiting. You are envisioning a big bright red trumpet shaped flower, right? Because everyone knows that hummingbirds like red flowers.

Except they don't.

In fact, the flowers hummingbirds like are only red because of bees.

Two researchers, Bradshaw and Schemske, did a super cool study which explains why -- as I will summarize here (Images of mimulus are also from this paper). Sadly, you need a subscription to get the full text. I'll do a super job summarizing it for you, but if you there is a lot more to it than the bit I describe here, so if you have a chance (especially if you are into evolutionary biology) read the whole thing.
So these researchers took these two very closely related species of Mimulus from California:

Mimulus lewisii, on the left, is bee pollinated, and Mimulus cardinalis, on the right, is hummingbird pollinated, and they show all the classic differences in color and flower shape of these two types of flowers. You obviously can't tell this from the picture, but they also produce different amounts of nectar, M. cardinalis producing much more for the benefit of the hummingbirds.

Because these two species are so closely related, they were able to make a fertile hybrid between them, and grew out a massive F2 population (as I explain here, F2 just means the second generation, and is the generation where you see all different crazy combinations of the genes of the parents.) This image shows a bit of the variation they saw:
As you can see, all the traits of the two parents are thoroughly scrambled, some with the color of one parent, but the shape of the other, just as you have may your father's nose but your mother's eyes. This includes the traits you can't see, like nectar production. For example, though the flower in the lower left corner looks much like M. lewisii, it may very well have inherited the gene for producing lots of nectar from M. cardinalis.

They took literally hundreds of these different F2 plants, put them outside, and watched how often bees and hummingbirds visited each plant. Which sounds like loads of fun. Sitting there, trying to watch 200 some different plants and keep track of every single bee and hummingbird that visits each one. Better them than me! But they did it, and then they crunched the numbers to find out what traits actually caused bees and hummingbirds to prefer different flowers.
For bees, the answer is much as you would expect. They visited lighter colored flowers that looked like M. lewisii more than the darker flowers. Hummingbirds, on the other hand, only really cared about one thing: nectar. The more nectar a plant produced, the more they visited it. They didn't care if it was pink or red or big or small -- they just wanted nectar.
How did they know which had more nectar? Turns out hummers are smart, smart enough to visit each plant once, then remember which plants produce the most nectar so they can then only come back to the ones they like. Which is kind of amazing. Makes me glad I'm not a hummingbird. Too much to remember.

This just brings up another question. If all the hummers care about is nectar, why are virtually all hummingbird pollinated flowers red? Why is this pattern of shape and color repeated over and over in different species? (as seen again here in bee and hummingbird pollinated species of wild petunias)

Well, it turns out hummingbird flowers aren't red to attract humming birds, but rather to hide them from bees! Birds have color vision very much like ours (which, as a random aside, is part of the reason there are so many colorful birds. Virtually all mammals (except apes like ourselves) are color blind, which is why mammals are so uniformly boring colored). Insects, on the other hand, see the world very differently. They can see ultraviolet light, and more relevantly, they can't really see red. So those bright red flowers that stick out so much to us and the birds are almost invisible to bees. Unnoticed by bees, the red flowers can keep all their nectar waiting for the hummingbirds, who then come everyday to drink nectar and, in the process, carry pollen from flower to flower.

So next time you see a red flower, don't think, "Oh! The hummingbirds will like that!" Instead think, "Aha! Hiding from the bees with that red camouflage!"

(Bonus animal color vision explanation: Lots of plants from New Zealand -- and almost no plants NOT from New Zealand -- have brown leaves (like this and this). Why? Because New Zealand has no native mammals (except bats), so all the major plant eaters were birds. To a color blind cow, a brown grass looks just the same is a green one, and both get eaten. But to a bird with color vision, a brown plant looks dead and doesn't get eaten. All of which goes to show this world would be a lot cooler without mammals.)

19 June 2010

Joining up

Currently I belong to exactly zero gardening related clubs, societies, or associations. When I was a teenager going through my rose phase, I belonged to The Rose Hybridizers Assocation, but since I've (mostly) grown out of roses, I've not been a part of such organizations. I did, once, attend a meeting of the Michigan Orchid Society, since I have never had, and never plan to have, an orchid phase, and I only attended under the coercion of a friend, I didn't join.

So I belong to nothing. And yet, there are all these gardening organizations out there, presumably full of cool, plant-obsessed people. People I could learn stuff from, share plants with, all of that sort of thing. So I'm thinking about joining up. Based solely on the recommendation of the good people at Arrowhead Alpines, I'm considering joining the North American Rock Garden Society (NARGS) and its local Great Lakes chapter. I'm not a rock gardener, but apparently these people are mostly just all-around unusual plant nuts, and membership in the national organization gives one access to an apparently amazing seed exchange, and the local chapter has members-only, kick-ass plant sales.

That all sounds pretty darn cool. And makes me wonder what other cool organizations are out there, that I don't know about? Do any of you belong to great gardening organizations? Which ones, and why do you like them? 

16 June 2010

New Plants: Dangerous additions

I made another little trip to Arrowhead Alpines (I know I said I'd TRY not to go again... but somehow...) and among other things, I got this little trio of plants that is making my garden look a little like  Danger Garden.
A lot of lovely spines...

 In more detail, I got this adorable (and vicious) Opuntia fagilis. I'd picked it up because it was so cute, then asked about the hardiness -- they told me it is a form from the most northernly known cactus population in Canada, and will laugh at mere Michigan cold.

This evil beauty is Acanthus syricus. Yes, acanthus! It has flowers just like your typical bears breeches (as you can see here) but the foliage is kicked up a notch.

And finally, this Eryngium venustum. This may not look quite as bad as the other two, but it is by far the most dangerous of the group -- the leaves are razor sharp. But I love its incredible, geometric lattice work of spines. I had one a couple years ago, which didn't make it through the winter, so this one is going in a sheltered spot near the foundation -- hopefully it will survive for me.

All of which makes me wonder, why do I like these plants so much? My mother-in-law (who, by the way, is awesome -- no mother-in-law jokes apply) always laughs at me about my "thistles." For me, I think, it is about visual contrast -- the soft, rounded forms of most plants look all the better for being sprinkled with a few daggers. At least I think so. What do you think about dangerous plants?

14 June 2010

The best smelling rose in the world

Perhaps I should just say the best smelling rose my nose has ever encountered. Which is still saying something. I used to be minorly obsessed with roses (in my teens... I sort of grew out of it) and have spent a lot of time sniffing the over 11,000 rose bushes in the Columbus Ohio Park of Roses when I lived in that town. Sniffing through that collection, and every other collection of roses I have come across, nothing comes close to the scent of Madam Ernst Calvat.
Not only is her scent strong (when she is in full bloom, I can smell her easily several yards away at the other end of the garden) but it is marvelous and evocative. I showed a flower to a friend once, and after inhaling deeply, she said, "Wow... that really... takes you places, doesn't it?" Smells are always hard to describe, but to me it is a wild, exotic, smell. Not quite floral, not quite incense, completely marvelous.
If you don't know the good madam, here is what she looks like in my garden:

She's a hybrid perpetual, and like most hybrid perpetuals (indeed, like most roses) she is a gawky, rangy sort of shrub, inclined to get mildew. Which is why, if you look closely in the picture you can see strawberries growing at her feet, and onions in the background. Roses to me are for putting in vases, so I grow them with my other cut flowers out back with the vegetables.
Here she is looking as she should, in a vase, with some Phlox 'Chattahoochee' filling the house with her incredible scent.

I just wish you could smell it too, through your computer screen. It would set you dreaming.

13 June 2010

Just because it is pretty

A little vase of flowers I cut recently from the garden:
Alchemilla mollis, Lathyrus niger, and a random snapdragon (Antirrhinum hybrid).

11 June 2010

Working together

The beds infront of my house are in their second year, and things are starting to come together. I'm particularly fond of this section at the moment:
Here we have my beloved cardoons, fronted with the stunning Allium christophii mixed with bronze fennel. (It suddenly strikes me that this is edible landscaping... not that I could bear to cut and eat any of it, but still. All three are vegetables.)
Believe it or not, when I started planting here last spring, I was planning all hot colors -- red, oranges and yellows accented with purple foliage and a bit of blue. But somehow I started planting silver foliage (because I can't resist cardoons), and I don't like yellow tones with silver, so all the orange and yellows got ripped out. Then I started planting purples and blues, and... I'm liking it. A lot. It will be interesting to see the look evolve as the summer goes on and my Salvia 'Black and Blue' (from tubers I saved from last year) and Crocosmia 'Lucifer' come into flower.