I planted ‘green tiger zucchini’ summer squash for the first time this year. I was surprised to see that they grew huge seed leaves, or cotyledons, that are much larger than those of other squash I’ve grown. I measured the leaf on the left as over 3.5 inches (9 cm) long.
The size of squash cotyledons is influenced by how much light they receive during germination; see “Changes in the cotyledons of Cucurbita maxima during germination.”
For more about seed leaves, see my post Seed Coats, Seed Leaves, True Leaves, & Mutant Kale.