'Cloche'

Cloche, a thing to cover plants when they are young and tender.  Makes a lot of sense.  Each plant gets it's own little greenhouse.  Retains heat and moisture and staves off killing frosts.

I suppose if I had a fine aristocratic nose to look down at people from, I might have the fancy glass versions ($25 each)

Or, if I was even lazier than I am and a spendthrift to boot, I could buy them in plastic from Amazon ($1 each).

I'm neither of those things.  I'm a cheap old bast.... um.... frugal gentleman.  The wife has aquariums, and that means distilled water in multiple gallon jugs at a time.  The resulting empty plastic bottles need only the bottom cut off to make a very serviceable cloche at my favorite price ($0).

This is why I have well started zucchini, butternut, and basil plants in zone 6b in mid-April.

Re-use, re-purpose, re-cycle.