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.)

Scientists (not) talking to gardeners

This gorgeous display of phalaenopsis is part of a study by a professor I know who researches (among other things) orchids.

How cool is that – right? Don't you wish he had an orchid blog to pass on all sorts of tips on how to get the darn things to rebloom after you buy them?
Well – not really. He actually doesn't know much more about growing orchids at home than anyone else. In fact, I've been to his house: He had one orchid, which was dying, just like the one on your windowsill. He knows and studies commercial orchid production – how to rapidly and efficiently grow baby orchids into the lovely plants in full bloom you can pick up at virtually any grocery store these days. In other words: He's NOT “one of the few scientists interested in talking to gardeners.”
I put that last line in quotes because it is a phrase I've seen often on Garden Rant to describe people like Jeff Gillman – as in “his is one of the few scientists interested in talking to gardeners."
Sadly, this is true: Very few scientists do research that directly relates to home gardeners. I'm a grad student in a horticulture department, and I know faculty who study everything from vegetables to flowers to conifers to turf grass to weeds -- but none of them study these topics in terms of the home gardener. They study breeding, watering and fertilizer at the nursery, light levels in commercial greenhouses, even marketing --  in short, they study everything required to get a plant in your hands walking up to the check-out counter at a garden center – and nothing after that point. This isn't just a quirk of one particular university. The same is true of the school where I got my bachelors degree, and of 99.99% of the research I see presented at academic conferences.
But why? Why are so few scientists interested in talking to home gardeners? The truth is, I think lots of them are interested – they just can't afford it.
As usual, it comes down to money. Before I landed (more or less accidentally) in grad school, I assumed academic research programs were funded by the university. Not true: Professors are more like small business owners than regular employees. When a new professor is hired they get an office, a telephone, and part of a salary (Increasingly faculty are only paid by the university for 9 months of the year). The money for laboratory equipment, staff, salary and fees for graduate students like myself, fees to use university resources like greenhouse space or plots at research farms, and yes, one fourth of their salary, they have to find themselves. To get the money to pay for all this professors spend a huge amount of their time applying for grants from industry groups and governmental organization like the USDA. In other words: They have to come up with research ideas that will convince someone to fork over the money to actually get it done -- and home gardeners don't tend to give out grants. A book for gardeners could bring in some money, but not enough to run a whole research program – certainly nothing compared to the 14 million (yes, million) dollar grant a professor in my department recently landed.
Want more scientists to talk to gardeners? Well, you're going to have to pay for it. Oh wait – you already do. That 14 million dollar grant I mentioned? Your tax dollars by way of the USDA. I'm not  running down government funding for basic research – those 14 million are going towards spectacular research. But wouldn't it be nice if a little of that money went to research we could use?  Maybe it is time we gardeners spoke up and convinced our government to make research on healthy, environmentally sound home gardening more of a priority – or rather, a priority at all -- so the scientists who are interested in talking to us are able to.

Where double flowers come from

Every wondered how plant breeders get from single flowers like this:

To big doubles full of petals like this?

(photo from jungle seeds)

Well, it starts with flowers like this:

Look closely (click on the image to expand it) in the center of each flower, and you can see little tiny specks of extra petals -- they're actually called "petaloids"

Here is what they look like carefully pulled out of each flower: (I highly recommend clicking on the photo to see them much larger)

At far right is a normal stamen -- the male part of the flower that produces pollen. The others are in various stages of conversion into petals. Keep going with this, and you get the full, frilly, double flowers you see in the second pictures. It only takes a very small change in the expression of a single gene to switch an anther to a petal -- so double versions of flowers pop up randomly all the time in nature due to random mutations, or in the genetic confusion of hybrids between species (which is what lead to the petaloids in these pictures). In the wild, of course, double flowers die out because they are usually virtually sterile -- and even when they aren't how is a bee supposed to get in there and pollinate them? But in the garden, we treasure them and keep them alive -- so much so that many people don't even realize that the classic rose:

Is a double version of a very simple flower with only five petals like this:

 

Trying this year: Determinate Tomatoes

I hate staking. I'll happily weed for hours on end, happy as can be. I'll spend a full day working hard with a shovel and smile all the while. But I hate staking.
Because of this, my tomatoes always end up sprawling in a tangled mess on the ground. I know they'll be healthier if I stake. I know it will be easier to harvest them if I stake. Because I know this, some years I actually go so far as to put stakes out in the garden, which resulted in my tomatoes being a wild mess with some stakes sticking out of the middle.

So this year, I'm going to try growing some determinate tomatoes.

The technical definitions of determinate and indeterminate just refer to where flowers are produced. Determinate plants produce them at the top of a stem, forcing new growth to come from new branches at the side of the plant, while indeterminate plants produce flowers along the sides of the stem, allowing a single branch to keep growing on and on and on.

 This means that determinate tomatoes grow short and bushy -- rarely needing to be staked -- while indeterminate tomatoes grow long and floppy -- and theoretically ought to be staked, though of course I never actually do.

I've steered away from indeterminate tomatoes up until now, though, because catalogs always define them a different way: They say the determinate tomatoes produce fruit which ripens all at once, while indeterminate varieties produce continuously all summer long.

But: Recently I've been reading something different: Tom Clothier on the tomato page of his quirky, very enjoyable website, says some there are determinate tomatoes, which produce a load of fruit and then stop, and there are vigorous or strong determinates, which keep sending up new shoots, ending in flowers and fruit, all season -- so they produce continously like a indeterminate, but minus the staking, and are usually much earlier than indeterminates.

Which sounds perfect to me... We'll see! If I can get tomatoes which produce well and taste yummy but don't turn themselves into a tangled mass, I'm all for it. I'm still growing my favorite indeterminate varieties, but I'm also going to be trying out these 4 determinate ones:
Al Kuffa
Mountain Princess
Gold Nugget
Subarctic Plenty

We'll see how they perform!
Anyone with experience with determinate tomatoes? If so, please leave a comment with your thoughts, and any varieties you'd suggest or warn against.

What the F?

Welcome to my explanation of the terms F₁ and F₂. I'm writing this in preparation for a future post in which I want to reference these terms -- I don't want to have to explain them in that post, and I think most people know roughly what they mean, but just in case, I'm writing this so I can link back to it for the sake of the confused
.
When you make a hybrid between two different varieties or species or whatevers the first generation is the F₁ generation. The babies of the F₁s are the F₂s, children of the F₂s are the F₃s, et cetera.
One talks about F₁s and F₂s a lot because they have special characteristics, which basically boil down to this: If I cross two different things, the F₁s will all be the same, and the F₂s will all be different.

Some real life pictures of this: For my research in grad school, I'm working with a hybrid of two species of petunia: Petunia axillaris, which is white, and the red flowered Petunia exserta.

 The F₁ generation of this hybrid all looks the same: Very, very pale pink flowers:

While a bunch of F₂ plants look like this: A random mix of all different shades of pink.

But WHY are the F₁s all the same, and the F₂s all different? Let me use another example: A couple years ago I made a hybrid between two tomatoes. One, Matt's Wild Cherry is (as you might guess...) a cherry tomato. The other, Black Krim, is not a cherry tomato. The cherry trait is controlled by a single gene: Have one or more copies of the dominate version (C) of this gene, and you make cherry tomatoes. Have two copies of the recessive version (c) and you make big fruits. So I made my two tomatoes have sex, and they had a bunch of little F₁ babies. Each F₁ got a copy of each gene from each of the parents. From Matt's Wild Cherry they got the dominate version C, and from Black Krim, the recessive version c. So all the F₁ plants had one C and one c, and since C is dominate, they were all cherry tomatoes. I then crossed the different F₁ plants with each other to produce the F₂ generation. Now each F₁ has one copy of C and one of c, so when they make babies, they randomly choose just one of the versions of the gene (sometimes C, sometimes c) to pass on to the next generation -- meaning among the F₂ plants, some will happen to get a C from both parents, some will get one C and one c, and some two copies of c – making the F₂ generation a mix of cherry and full sized tomatoes.
The exact same process works for all the other genes in the tomato: There are genes for the dark color of Black Krim, genes for the sweetness and flavor of their fruit, how they grow, when they flower, and so on. All the F₁ plants are the same with exactly one version of each gene from each parent, but the F₂ will be a wild mix of all the different possible combinations of the different genes from the two parents.

And why should you care? Well, seed companies use this all the time to their advantage. When they are developing a new variety of tomato, they need it to be uniform – all the seedlings need to look the same (if you buy a packet of Early Girl seeds, and some plants came out as cherries, and others yellow, you wouldn't be too pleased, now would you?) The easiest way to make a variety uniform is inbreeding: Cross closely related plants each generation and you'll eliminate genetic variation resulting in perfect uniformity. But just as it isn't smart to marry your sister, inbred plants have problems (well, usually – some plants, like squash, are actually fine with it). So what to do? Well, if you take two uniform, inbred lines, and hybridize them the F₁ generation will be not be inbred, because it is a hybrid, but will be uniform because it is a F_1. Problem solved. And even better, if a company sells F₁ hybrids, you have to buy new seeds every year because if you save your own seeds, they will produce the F₂ generation when all chaos breaks loose. So F₁ hybrid varieties are not only an easy way to make healthy, uniform varieties, they also are a good way to ensure repeat sales (Though to be honest, people saving seeds isn't much of a concern to seed companies – the bigger issue is other seed companies using their varieties to develop similar, competing varieties, something releasing F₁ hybrids makes that much harder to do.)

So that's it, really: The numbers after the F indicate what generation you are talking about, and the ones we generally care about are the F₁s, which are all the same, and F₂s, which are all different. I hope you now feel extremely wise.