Index/Collect from Descendants

Leeweber

In this sheet, I have a column [Groups] which is a parent column to multiple "Groups", each of which is a parent column itself to tasks associated with each group.

I need help putting a formula in [Start Date] of the parent row that would give me the very 1st value from [Date] column that is a Descendant of [Groups]@row

This formula gives me the correct row # from the Groups column
=INDEX(DESCENDANTS(Groups@row), 2)

This formula is giving me an error
=INDEX([Date]:[Date], DESCENDANTS(Groups@row), 2)

Thanks in advance!