TT #411 · Parashas Reeh · Seventh Aliyah · Passuk 16:13
The festival of Sukkos you shall make for yourself seven days, when you have gathered in from your threshing floor and from your winepress.
Torah Temimah points to Maaserot / Rosh Hashanah.
Sefaria — Maaserot / Rosh Hashanah
English: "From your threshing floor and from your winepress" — "from your threshing floor" and not all of your threshing floor, "from your winepress" and not all of your winepress; from here we learn that produce is subject to tithing once it has reached one-third of its growth.
Derash on the verse (Maaserot) — liability for ma’aser begins at one-third growth.
Produce becomes subject to the laws of ma’aser when it has reached one-third of its full growth.