Sunday, October 5, 2014

Hot Peppers

At the beginning of summer one of our big box stores was offering all kinds of little pepper plants for next to nothing. So we probably took home more than we will ever want to eat.
The plants grew very well in pots on the patio where they used to get morning sun and then shade from the roof as the sun rose to the zenith. Now that autumn is upon us Arizona still gets hot, but the sun rays come in at an angle that exposes the peppers to so many more hours of light and heat that actually have to water them twice a day.

With the help of our nitrogen rich compost and some doses of Epson Salt to replenish the soil's magnesium the plants are growing beautifully. While the Jalopenos are towering over my head by now, Tabasco and Cayenne have turned into more delicate and very ornamental plants, studded with colorful small fruits. My old volunteer bell pepper plants are also constantly producing small but tasty pods. We are very much enjoying a wall of healthy green leaves that we already shared with two generations of leaf-cutter bees.

No one else has attacked our pepper plants yet. That somewhat surprises me because they have close relatives in our ecosystem, the red, spicy, pee-sized chiltepins, so they should have natural consumers.  'Of course', the Tucson Backyard Gardeners say 'Their spiciness protects them'. With this in mind, the gardeners produce concoctions of hot pepper that they then spray on all kinds of plants to prevent all kinds of  'pests'.
It sometimes works, probably because they usually add more than one ingredient to their 'organic pesticide' so it's never clear which component is actually effective. Or the pest was the household dog, and dogs do not like pepper spray  in their sensitive noses. But......

The ingredient that makes peppers hot and spicy and in high concentrations irritating to mucous membranes is called Capsaicin. It is present throughout the fruit and most concentrated in the placental membranes where the seeds are attached.
Capsaicin is known to stimulate temperature and pain receptors in mammals (like rodents, dogs, humans and bears). 
When I was working at my Ph. D. at the Max Planck Institute in Bad Nauheim, Germany, a friend of mine, Herbert Schmidt, tested the effect of capsaicin on  birds (he is an electro-physiologist and worked on tissue samples). He could show that while mammalian thermo and pain receptors both responded to capsaicin applications  (some of its therapeutic value is based on that effect), a similar response to capsaicin was not found in bird tissue.

When I came to Arizona, the folks at Native seed Search offered a plausible explanation: The red, attractive fruit of chiltepins, tabasco, jalopeno et all are probably exposed to several kinds of 'harvesters': Small mammals like packrats and mice, big mammals like javelinas, bears and humans, and birds.
Plants produce fruit to disperse their seeds. Many are juicy and inviting to attract animals to do the job, carry the fruit away, eat the juicy flesh but hopefully leave the seeds unharmed.  But if  rodents would feast on peppers, they would probably eat the juicy flesh and also chew up the seeds. This would destroy them and make them useless for plant propagation. So pepper plants evolved to load the fruit with capsaicin to make them rather impalatable to rats, squirrels et al.

But that's not good enough. The seeds are not supposed to just drop down under the mother plant to germinate in its shade and let the seedlings compete with each other. To thrive, they need to be dispersed.  So the inviting fleshy fruit is not a forbidden one to every harvester:  Birds suffer no ill effects at all because their receptors do not react to capsaicin. So they are free to eat the peppers. Not having teeth, they swallow the seeds whole and pass them through their digestive system, planting new pepper plants in their wake.
Perhaps even big mammals who don't bother to crack open every small seed would eventually excrete them in a viable state. The capsaicin response is dose related, meaning that a big bear or human may enjoy a delicate tickle where a small rat would suffer very serious heartburn. So maybe?

Anyway, the bright red, inviting, spicy peppers that signals 'stop' to rodents and other small mammals, can be an invitation to others.
(Sweet bell peppers are the result of selective breeding and do not occur in the wild)

I knew those research results and theories, but until today, the practical experience was missing. Sure, our packrats are leaving the peppers alone, so are our dogs, and we humans love them in small amounts. But the birds???

By the beginning of October, the candle-like upright Tabasco Peppers finally ripen, softening and turning from pale white to orange. (Wind and dogs have been playing with the labels that I was keeping with the pots, so there may have been mix-ups, but it's either serrano, tabasco or cayenne.) Yesterday I noticed that several fruits were shredded open on one side.  

Today during breakfast we finally cought the 'culprit'in the act.  Chattering happily a Verdin was intensely at work in in the Tabasco plant. Catching insects? Snacking on nectar from the few remaining flowers? No. He was going for the fruit. He devoured the fruit flesh and happily pecked at the seeds. Half a day later, most of the orange fruit were more or less gone, seeds and all.

 I am happy to have finally witnessed the story in real life and I am also glad that just a day earlier I had the bright idea to finally pick a bunch of peppers and pickle them in sweet vinegar.