> For the complete documentation index, see [llms.txt](https://swatplus.gitbook.io/io-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://swatplus.gitbook.io/io-docs/introduction-1/databases/plants.plt/untitled-12.md).

# frac\_hu2

Fraction of the plant growing season or the total potential heat units corresponding to the 2nd point on optimal leaf area development curve

Please see the explanation given for parameter [lai\_pot](/io-docs/introduction-1/databases/plants.plt/untitled-15.md) to obtain additional information about this parameter and methods used to measure it.