I honestly don’t remember where I read it, but somewhere in my studies I’ve come across the statement that the right time to start taking eggs out to hatch is when the mulberry leaves are the size of a mouse’s ear.
Without getting into a Monty Python skit about whether it’s an African or European mouse… this is what I’m looking for:
These tiny unfurling leaves will be followed quickly by catkins and then bursts of leaf after leaf. Mulberry trees are famous for being late in the spring (Morus, the mulberry, is believed to derive its name from Latin mora, meaning “delay”, because of the tardiness of its buds) but because of their cautious slowness I have never seen them blasted by a late hard freeze. Once the Bois d’arc tree leafs out, then I’ll be sure of things and feel comfortable planting my tomatoes and peppers.
When the leaves are mouse-ear sized (for a given value of mouse), I take the eggs out of cold storage in the refrigerator, and put them in a small container to warm up.