# Data sources and provenance

> Canonical URL: https://www.poaindex.com/ai/data-sources.md

PoaIndex aggregates public sources. It does not invent trial results or retail availability.

## NTEP

The National Turfgrass Evaluation Program (NTEP) publishes turfgrass trial reports. PoaIndex’s historical quality corpus focuses on annual site-level **Turfgrass Quality** observations:

`species + trial + data_year + site + entry + turfgrass_quality`

Commercial asterisk (`*`) on NTEP reports means the entry was marked commercial in that report year. Absence of `*` is not “never commercialized.” Historical commercial marks are **not** live retail inventory.

## U.S. Census ZCTA

Five-digit postal codes resolve to Census ZCTA representative points (Gazetteer). Location is approximate postal geography, not an exact USPS delivery address.

## AOSCA Grass Index

AOSCA confirms official variety identity where a match is confirmed. Confirmed matches may affect **consumer display names** only. They never change scientific scores or ranks.

## National turf-zone baseline

PoaIndex assigns each supported ZCTA to a broad turf climate zone (`cool-season`, `transition`, `warm-season`, or `unclassified`) via methodology **turf-zone-v2**. Turf zones answer which species groups are generally appropriate; they do not pick a single best cultivar.

## Servable corpus tip (ntep-quality-history-v1)

The certified v1 tip includes eight species and excludes Buffalograss (deferred). See also https://www.poaindex.com/ai/species/index.md.