You shall keep the Feast of Harvest, of the firstfruits of your labor, of what you sow in the field. You shall keep the Feast of Ingathering at the end of the year, when you gather in from the field the fruit of your labor.
Exodus 23:16 ESV

Although all three feasts of ascent are harvest festivals, they are referenced slightly differently. Shavuot is more explicitly called the “Feast of Harvest”, while Sukkot is called the “Feast of Ingathering”. Passover is the “Feast of Unleavened Bread”, but it includes the early firstfruits offering from the spring barley harvest.