Soil Prep Guide
Amending compacted, clay, and sandy soils.
Most Willamette soils are heavy clay sitting on top of more clay, compacted by a century of foot traffic. Amending soil is not about replacing it. It's about persuading what's there to remember how to breathe.
Soil prep is the single highest-leverage investment in a planting, and the one most often skipped. Plants installed in well-prepared soil establish faster, root deeper, and need less water for the rest of their lives.
For heavy clay: the goal is structure, not nutrients. Incorporate 3 to 4 inches of coarse compost (not fine compost — coarse, with chunks) into the top 8 to 10 inches of soil. Add a thin layer of pumice or coarse sand only if drainage is severe. Avoid adding 'regular' sand to clay — it makes concrete.
For sandy soil: the goal is moisture retention and biological activity. Incorporate 4 to 6 inches of fine compost and consider adding aged manure. Sandy soils benefit enormously from a permanent mulch layer maintained year-round.
For compacted soil: aerate first, amend second. A broadfork, a deep digging fork, or even repeated passes with a garden fork can break up compaction without inverting layers. Then amend the surface and let roots and worms do the rest.
Never till wet soil. The squeeze test: take a handful of soil and squeeze it into a ball. If it crumbles when you poke it, it's ready to work. If it stays in a sticky ball, walk away for a week.