S U N D A Y S O U R D O U G H

I wrote this post a few weeks ago, when most of the leaves were actively changing color, but neglected to post it. Despite an unseasonably warm month, most of the trees in NYC have dropped their leaves by now. The study of when and why things in the natural world change, on a cyclic schedule, is called "phenology," and this extension of the growing season--leaves coming out earlier in the year and falling later--is a consequence of a changing climate. It's an area of intense study, and we should talk more about it at some point!

For now, let's talk about what happens when leaves change color, and why they do so in the first place.

Not all trees shed their leaves in the fall, but those that do respond to an array of different environmental indicators to tell them that it's time to stop growing and retreat into rest-mode for a few months. Temperature plays a role--trees respond to chilly mornings and frosty days--but so does the length of the day. Once nights lengthen past some threshold value (which varies by tree type, location, and other genetic factors), deciduous trees start to draw all of the useful sugars, carbohydrates, and other biologically expensive equipment out of their leaves and back into their trunk-bodies. It's as if they'd laid out their patio furniture in their leaves for the summer, the chairs and the umbrellas and the cushions, and then carefully put everything away in the basement for the winter.

The molecule the trees are most interested in retrieving is chlorophyll. Chlorophyll is the pigment (colored molecule) that captures photons from sunlight, strips those photons of their energy, and diverts that energy toward the building of sugar molecules, which the tree then uses for growth. It's the base molecule for photosynthesis, and one of the most important evolutionarily-developed molecules we know of. Chlorophyll is a pretty complex molecule, too, with some biologically expensive components in it--metals and other elements that aren't really easy for a tree to get its hands (roots?) on, so plants are heavily incentivized to retain as much chlorophyll as they can, rather than letting it fall off along with the leaf and decay on the ground.

Chlorophyll appears green to the human eye. There are some other molecules that help with photosynthesis by absorbing photons with different energies, and those molecules appear yellow and orange. For some reason, not yet thoroughly explained, trees choose to jettison these molecules with their leaves, sucking only the chlorophyll back into their limbs. As the green chlorophyll drains away, the yellow and orange pigments take visual precedence.



The red and purple pigmentation we see in trees like sugar and Japanese maples comes from a different source: a type of molecule called "anthocyanins." These molecules are antioxidant molecules, produced only in the fall from the leftover carbohydrates in the leaves, and we still don't know exactly why they're produced. Because they're antioxidants, they may protect the slowly-draining chlorophyll from sunlight oxidation damage, or they might play some other role in limiting water loss during the fall; it's not totally clear, yet.

I love that, don't you? One of the most basic, fundamental, beloved events of the fall still holds questions for us. Scientists of the future, there's so much work left to be done!

Anyway, the TL;DR version: deciduous trees have light-trapping molecules in their leaves that they don't need to use during the winter, because they aren't trying to trap light, make sugar, and grow; they're just trying to survive until the next growing season. These molecules are green. When the trees call their green molecules back to the home base in order to save and recycle their valuable parts, the orange and yellow molecules that are left behind in the leaves are uncovered, and the leaves turn those bright colors. Other red and purple molecules join those yellow and orange ones, for reasons yet unknown.

My experience with savory pies began and ended with my New Zealand sojurn, years and years ago. N requested chicken pot pie, though, so I dug into some cookbooks and attempted one. I decorated it with pie-crust leaves in honor of the fall (which, to be clear, I really dislike. Summer is the greatest, and fall signals the end of light and warmth and happiness. Go away, stupid fall. Shorts and tank tops  >>>> pants and sweaters).

Anyway, here you go. Go check out the leaves in your area. What trees change sooner than others? Which trees turn which colors?



Recipe: Chicken sweet potato pot pie in a sourdough whole wheat crust

I made the pie dough with some of my whole wheat starter sometime last week and stashed it in the fridge, tightly tucked into plastic wrap. I intended to make an apple cheddar galette, or a squash ricotta something, but the other night we a) didn't have anything made for dinner, b) I'd just seen the BA recipe for a squash/chicken pot pie, and c) we happened to have all the ingredients for this already. Win! I combined this Joy the Baker recipe with this Bon Appetit one and made a few other tweaks. The whole wheat sourdough crust has a LOT of flavor + texture, which I like, but you may not, so feel free to sub in a regular pie crust here. OR just use a some puff pastry on the top, if you're feeling like you want a super easy version. Here's my variation:


Whole wheat sourdough crust:

• 2.5 cups white whole wheat flour
• 1.5 sticks!! of butter (12 tablespoons), straight from the fridge
• cut the butter into small chunks. I usually do this by slicing a stick into ~12 pieces, then cutting each slice into 4-6 little chunklets
• half a teaspoon table salt, not kosher
• 1 cup starter (100% hydration)
• note: feed your starter in the morning if you plan to make the dough in the afternoon, or the evening before if you plan to make the dough in the morning. Cool the starter down before you make the dough by sticking it in the fridge for an hour or so.
• a few tablespoons of cold water 
• if I'm very prepared, I put a cup of water in the freezer about 20minutes before I make the dough. If not, I just use the coldest water I can get out of the tap.