Coffee grows on trees, but it can also grow underneath and around them. Coffee is sometimes labeled as "shade grown" and in order to understand the benefits of shade grown coffee, it is important to review the different ways in which coffee in grown.

Arabica vs Robusta

Coffee is not a uniform crop; there numerous varietals of coffee grown around the world. The main botanical division is between Arabica coffee and Robusta coffee. Robusta coffee can self-pollinate and grows at lower elevations where it can endure hotter temperature and more aggressive sun exposure. All specialty coffee (aka the good stuff) is Arabica coffee, which is insect-pollinated and and grows at higher elevations where it requires milder temperature and less sun exposure.

Finding Balance: Shade vs Sun

Coffee beans are the seeds of the fruit of the coffee tree, known as "cherries." The balance of temperature and sun that yields optimal cherry development differs between different varietals of Arabica coffee. There are some varietals, such as those grown on larger plantations in Brazil and Colombia, that do hold up under full sun. These heartier varietals tend to be some form of hybrid seeds selected for field performance that maximizes use of space. In terms of pure efficiency, shade grown coffee is not an efficient use of space because it initially means less trees per hectare and less harvestable coffee per hectare, although this can change over time. However, coffee grown under shade offers many other benefits, benefits that extend beyond simple yield calculations. Shade grown coffee is categorized as an agroforestry system. Agroforestry is just what it sounds like: agriculture merged with managed forests. Like any other tree, coffee needs sunlight and too much shade can be worse than none at all.

Green, unripe coffee cherries in development.

Brass Tax: Costs vs Benefits

Shade grown coffee does not subscribe to a single model; its cultivation is far more varied than that of full sun coffee. Different trees can be intercropped with coffee to achieve different goals. Some species of trees are nitrogen fixing and make key nutrients readily available in the soil. The falling leaves from these trees provide an additional layer of decomposing matter that acts as one kind of fertilizer. These falling leaves (known in the business as "leaf litter") also act as a preventative layer to keep weeds from growing up between the coffee trees, therefore lessening or even eliminating the need for herbicides, which are expensive and time consuming to apply, in addition to being environmentally detrimental. Shade trees have to be "regulated" or pruned to keep them from entirely blocking out the light that coffee needs to grow. Pruning requires manual labor, which quickly becomes an expensive additional cost for producers, whose highest cost is already the manual labor necessary to harvest coffee cherries by hand. Shade regulation also requires planning and timing, adding another variable layer to farm management. It's tricky, but plenty of producers understand the benefits and are willing to take on the work even if their coffee isn't sold for a premium under a "Shade Grown" label. Each producer practicing agroforestry has a different motivation and therefore a different plan of execution. Reasons for planting coffee as part of a shade system can relate to producers' concerns for soil and environmental health, financial strategizing, or the desire to be stewards of habitats for birds and mammals. Over time, studies have shown that shade systems also increase the yields of coffee trees. Working under agroforestry systems does not produce the immediate results that agrochemical fertilizers deliver, but in the long run shade coffee can offer more cherries per tree and per hectare than its conventional counterparts. Coffee agroforestry is integral to the ways in which today's coffee farming must adapt to changing climates, including rising and erratic temperatures and inconsistent, sporadic rainfall and periods of drought.

Certification: For the Birds

The only organization offering an official seal verifying that coffee is grown as part of a shade system is the Smithsonian Migratory Bird Institute with their Bird Friendly label. The SMBI applies Bird Friendly status to farms already certified organic; organic farms use shade as a tool, as mentioned above, to eliminate the need for herbicides. Bird Friendly shade grown coffee is cultivated in conjunction with the specific species of trees that provide habitats for migrating birds. Not all shade systems offer viable habitats, so Bird Friendly shade grown coffee is only one subsection of coffee agroforestry systems. Rainforest Alliance certification also requires farms to have some sort of shade trees planted with coffee, but it does not require these trees to create specific habitats. Rainforest Alliance looks to the health of the soil and whole ecosystems, and its reason for requiring trees is a much to stabilize soil and protect water sources from runoff as it is to encourage biodiversity of fauna. It is true that any agroforestry system invites more species of birds, animals, and insects than full sun coffee, but this varies depending on the other goals of growing coffee alongside other trees. Some other trees intercropped with coffee include avocado, orange, and banana trees. Fruit trees offer an additional source of income for producers, allowing them to diversify the crops on their land and not be subject to one lone market price that fluctuates wildly. Having multiple crops cultivated together offers harvests at different times of the year and hopefully offsets and major drop in the market price of one crop.

Avocados and coffee on Miguel Badilla's Rainforest Alliance certified farm in Santa Maria de Dota, Tarrazu, Costa Rica, 2012

Avocados, nitrogen fixing trees and coffee on Miguel Badilla's Rainforest Alliance certified farm in Santa Maria de Dota, Tarrazu, Costa Rica, 2012

Hardwood trees are also frequently planted with coffee. These may provide some habitats for birds, but mostly they provide medium and long term financial insurance. Hardwood trees like mahogany, walnut, cedar, and oak take many years to grow, but when they are harvested can be sold for a significant sum. Producers plant hardwood trees as a legacy for their children. Some producers also harvest hardwood on their farms for their own construction of furniture for their homes and farms. Coffee agroforestry is also part of larger carbon sequestration schemes and there are also discussions of ways producers can be paid for the carbon credits their farms generate. Coffee produced with minimal or without agrochemicals can quickly become carbon neutral, since coffee plants are themselves trees and therefore pull carbon from the atmosphere.

Shaded coffee at Finca Monte Claro organic farm in Turrialba, Costa Rica

Real World Experience

Different countries and different regions face different challenges in growing coffee and for some shade coffee is a no-brainer, while for others it is simply not feasible. Shade trees above coffee in places with particularly high moisture content can create a sort of tarp that incubates fungi that destroy coffee leaves. In other places, shade can create the perfect incubator for the microorganism that kills pesky bugs that eat the coffee cherries. Working with coffee agroforestry requires an initial, careful assessment of the conditions of a given farm. Some producers carry this out on their own and others have the benefit of resources provided by agricultural research institutes or national coffee offices. Usually, smaller farmers are the ones who opt to adopt shade and agroforestry models, but larger plantations have also demonstrated success, notably Aquiares Estate in Turrialba, Costa Rica. Turrialba was the first place I visited in my coffee travels during 2012-13. Read more about my observations on coffee, climate, and tropical agriculture at whencoffeespeaks.com and find out how producers themselves describe coffee production in When Coffee Speaks: Stories from and of Latin American Coffeepeople.

Depending on who you ask, acidity in coffee is either a) the cause of heart burn and/or acid reflux, or b) the source delicious fruity complexity, a highly desirable characteristic of the best coffees. Armed with a digital pH probe and inspired by an episode of Sesame Street I was watching with my son, I set out to learn a little bit about acidity in coffee. Basically I wanted to answer two questions:

1. Does the acidity we taste in coffee correlate in any way with the actual pH of the coffee?
2. If there is a difference, can it be significant enough to support claims made by roasters of "low-acid" coffee?

Before I bore you with text, here are the pH readings I took over the weekend: Substance, pH Whole Milk, 6.9 NYC Tap Water, 6.7 Sumatran Coffee (low acidity), 4.6 Panama Coffee (medium acidity), 4.5 Kenyan Coffee (high acidity), 4.3 Apple Juice, 3.8 Grapefruit Juice, 3.6 Blueberry Lemonade, 2.9

*If it's been a while since you took chemistry in high school, a pH of 7 is neutral, and a lower pH means more acidity.

Coffee Acidity: Flavor vs pH

I went into this experiment assuming that there would be absolutely no pH difference between coffee that tasted very acidic or not acidic at all. Surprisingly, there was a small but direct correlation with flavor and pH. To perform the experiment, basically I brewed three coffees at the same time, 4 minute brew time, 16:1 brew ratio, then let them cool to about 100 ℉. Kenya is a region known for very high acidity (in a good way) and this coffee in particular was SL-28, the most acidic varietal. Sumatra is a region known for very low acidity, and this was a particularly flat Sumatra. We didn't ship it in our subscription (and no, it wasn't from Bespoken, that picture above is just to show off my fancy lab-ware). The Panama was somewhere in-between. You'll just have to trust my tastebuds on that one. Or as it turns out, my pH probe. Because I went into this experiment expecting to see no difference in pH, I sorta skimped on the freshness. The coffees I sampled were 3 weeks old, and the acidity was noticeably lower (in terms of taste) than when they were fresher. I was concerned that freshness would mess up the pH readings because fresher beans contain carbon dioxide, and CO2 increases acidity. However, based on these results, I'm curious to test a batch of coffee 3 days off roast to see if the difference is more noticeable. Stay tuned for a Part 2 where I will present more data on fresher coffees, and track changes as they age.

Low-acid Coffee and Acid Reflux

I have no doubt that people experience stomach issues from coffee, but I strongly doubt it has anything to do with the acidity. In addition to my list above, here's a list of pH values for common foods from the FDA. If you think coffee is bad, you probably also can't eat almost any fruits, tomato sauce, or napoleons and eclairs. More importantly, the difference in pH between very acidic and very flat coffees is probably not significant enough to cause or prevent stomach issues. So if you have been, or are considering switching to a low-acid coffee, I recommend you think twice. It's more widely accepted that the caffeine in coffee is what causes irritation because it stimulates the release of more stomach acid. It's an easy theory to test, try a caffeine pill, a red-bull, or 5-hour energy. Tea and soda also have caffeine, but in lower doses.

Coffee Flavor

The reason I'm so opposed to blaming heartburn issues on pH is because acidity brings with it a ton of interesting fruit flavor and complexity. Have you ever had a cup of coffee that's naturally sweet and tastes like blueberries without any weird additives? If not, then you're missing out. Subscribers to Angels' Cup get to blindly sample up to 208 different coffees per year! Insane variety and blind tasting are the only way to learn how different origins taste.

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We recently added a feature to the Angels' Cup coffee app that lets you record brew methods AND the results.

If you're familiar with brew methods like the Chemex or Aeropress, recording the brew method is straight forward. As you can see in the screenshot to the left, you can record things like temp, grind, brew time, coffee, and water weight. When you have a coffee and water weight entered, the app shows you your brew ratio. There are a few apps out there that let you record brew data, but if you really want to learn how to make better coffee, you should also keep track of the results. To help you do this, we built a 2-axis chart to record your coffee's strength and extraction. Coffee strength is easy to discern. It either tastes too watery or not watery enough. If your coffee is ever too strong, you can solve the problem by adding a little water to it! Extraction is a little more challenging, and might take some practice to understand. Coffee people usually refer to extraction in terms of sour and bitter.

Sour

If coffee is under extracted it will taste sour because the fruity acidity comes out first. Think about the tart flavor of citrus fruit, or granny smith apples. Those flavors come from acidic compounds found naturally in fruit, and often can be quite pleasant. Candy is often loaded with the same types of acidic compounds, think about Jolly Ranchers or Starbursts. However, for these sour notes to taste good in a cup of coffee, they need to be balanced with the sweetness and even some bitter notes that develop later in the brewing process.

Bitter

If coffee is over extracted, it will taste bitter. Think about the flavor of really dark chocolate, garlic, or medicine. The bitterness in coffee takes longer to develop than sour or sweet notes, but can quickly come to overpower a cup. Here's a quick table to help you fix bad coffee: Flavor, Brew Time, Water Temp, Grind Sour, Increase, Decrease, Finer Bitter, Decrease, Hotter, Coarser It's easy to read about how something tastes, but how easy is it to pick up on in the cup? Understanding extraction, and training yourself to pick up on sour vs bitter, can be a challenge, but a fun one! The best way to really understand coffee is to deliberately brew multiple cups incorrectly, and try them side by side.

Experiment 1: Extraction through brew time

An easy way to mess up extraction is brew time. For this experiment, you will need a "submersion" brewer, one where the coffee grounds are suspended in water with no drainage (i.e. aeropress, french press, clever). A V60 can also work because the filters are thin enough to brew super fast if you want, but a Kalita or Chemex are bad options. You'll also need good coffee beans with at least medium acidity. You're going to make three cups. For one, just follow your normal recipe. For another, cut your recipe time in half, and for another double your recipe. For most people, that will probably mean a 2-minute brew, a 4-minute brew, and an 8-minute brew. When they're ready to try them side-by-side, what do you notice? I like to think of it as treble and bass. The under extracted coffee will have all treble and no bass. The over extracted coffee will have the bass dialed up. What if the experiment didn't work for you? Either a) your beans weren't very good or were stale, and didn't have treble or bass to begin with, or b) it just takes time to develop a palate, try again with 1, 4, and 12-minute brew times.

Experiment 2: Extraction through brew temp

This one is tricky, so buckle up. First, you need a variable temp electric kettle or a kettle with a thermometer. If you have that, make three cups of coffee, the first one at 210℉, the second at 195℉, and the third at 180℉. What you'll probably notice is that temperature affects the sour/treble notes, significantly more than the bitter/bass notes. Now here's where it gets tricky. Temperature doesn't simply increase or decrease extraction, it affects the rate at which specific compounds dissolve, namely acids and carbohydrates. The hotter the water, the more acidity and sweetness you will get, keeping all else equal. However, you will also taste a shift in the nuance of the acidity and sweetness, and this shift will be different for every damn coffee. Brewing a sweet coffee at lower temps seems to produce a beautiful candy-like sweetness. At higher temps we seem to get more of a starchy, bread-like sweetness. This might be acceptable if it's the only sweetness a coffee offers, or if the coffee needs sweetness to balance some bitterness or sourness. The basic rule of thumb I'll offer is this. For sour coffee, decrease temp. Yes that will reduce extraction, but think about cold brew as an extreme example. It's never too bright. If your coffee is bitter, increase temp. It won't pull out more bitterness, but it might pull out more acidity and/or sweetness to balance the bitter. And that's the basis of 'dialing in' a coffee recipe! You start with strength, and then adjust brew time and temp to get the perfect balance of treble and bass for a given coffee. Hope that helps, and addresses some of the comments below. :)

Experiment 3: Extraction through grind size

This is actually the hardest variable to experiment with. On something like a French Press, grind options are limited by what will pass through the filter. For filter brewing, changing the grind size will greatly affect your brew time. The finer you grind, the slower your brew time will be. That being said, one of the best tricks to making great coffee is to figure out exactly how fine a specific method needs to be. Go very fine, see if the coffee comes out bitter, then re-try with coarser coffee and a shorter brew time. At the end of the day, reading will only get you so far, you have to be willing to experiment. Don't think of it as a waste of beans. Gulping coffee without paying attention to flavor is a waste, experimentation is the best possible use of good beans. So set aside some time this weekend to have fun with your coffee!

Want to try more coffee?

Angels' Cup is an online coffee tasting club where subscribers get to blindly sample up to 208 different coffees per year, from over 100 top 3rd wave roasters. Small samples sizes mean you get to sample more coffees for less money. Tasting flights start at only $8.99!

Join Angels' Cup Today!