Our first year in Costa Rica, we applied to the Instituto Costarricense de Electricidad (ICE) for free reforestation trees. A few months later, a batch arrived. ICE runs three forest nurseries, in Cachí, La Garita, and Tronadora, producing hundreds of thousands of trees a year. Their operating philosophy is refreshingly indiscriminate: any tree is a good tree, whether it's a true reforestation native, a garden ornamental, or a plantation lumber species. You sign up, you wait, you receive trees.

It isn't a coincidence that a national electric utility runs the country's most ambitious tree giveaway program. The logic traces back to 1956, when ICE first moved to protect the watershed above the Reventazón River, and it hasn't really changed since. Forest cover on a slope means rain soaks into the ground instead of running off it. That recharges the nacientes, the springs, that feed the rivers ICE dams for power. More forest, more groundwater, more electricity. It's a simple equation, and I still think it's one of the better government programs I've ever encountered.

We tried, that first year, to keep our new trees labeled and identified. We staked a name tag next to each one, photographed the leaves, ran searches trying to confirm what we'd actually been given. What it might look like mature. How it might behave once it found its place in a forest community instead of a nursery row. It was a piecemeal effort in a climate that was still entirely unfamiliar to us, squeezed into the gaps of everything else that first year demanded. Looking at that planting now, only a handful of those original trees are still standing.

This compendium is my real reckoning with what ICE actually gave us, annually for five years now. It started, unglamorously, with a sprained ankle that kept me at my desk for the better part of two months. I finally did the identification work properly instead of hastily. I'd find the best available photo of a mature specimen, one without flowers or fruit crowding the frame, just the plain architecture of the tree. I'd print it out and trace its morphology in ink: trunk, branching structure, the logic of how the canopy held itself up. Then I'd come back over that ink with watercolor, looser this time, evoking the foliage instead of rendering it exactly. Alongside the drawings I started keeping spreadsheets, height, family, range, wood density, and the spreadsheets slowly grew into what are now the written notes.

Somewhere in those two months at the desk, I had to admit something about my own taste that this project eventually pushed me past. I love dark, intact canopy forest, the kind pioneer species can't grow in, the kind that takes decades or centuries to build. Given the choice, I'll always be drawn to the climax trees, the emergents that break above everything else, the hardwoods that hold their ground for a hundred years. Pioneer species, by comparison, seemed almost beneath notice. Scrubby. Short lived. The trees you tolerate on the way to the forest you actually want.

It took a long time, and a lot of species entries, to walk that bias back. Pioneers aren't the lesser draft of a forest. They're the only reason a forest gets a chance to be drafted at all. They're the ones willing to grow on bare, sun blasted, landslide scarred ground that nothing else will touch, soil too exposed and too hot and too abandoned for anything patient to survive in. They grow recklessly fast because they have to. They're racing to close a canopy before the grasses and vines choke out everything beneath them. In doing that, they rebuild the microclimate, the shade, the humidity, the leaf litter. By the time I'd drawn and researched enough of them, I'd stopped seeing pioneers as the lesser trees and started seeing them for what they actually are: scrappy, intrepid, structurally doomed, and doing more to build the eventual dark canopy than any climax tree ever could on its own.

That shift in how I saw pioneers is really what convinced me there's no other sensible way to organize these trees than by successional guild. Guild is the only frame that tells you why a tree looks and behaves the way it does, because it tells you what the tree is racing against, what it's willing to tolerate, and what it's ultimately built to hand off to something else. A pioneer's soft wood and its urgency aren't separate facts about it. They're the same fact. In Part 2, I'll look more closely at how you actually put these guilds to work together, layering them into real reforestation strategy on real ground. But here, in this section, I wanted each guild to stand alone first, to be understood on its own terms before it gets folded into a plan.