After Jack retires, he and Bitty get a house somewhere equidistant from their respective homes, someplace with a nice bit of property, quiet, huge kitchen, etc.
And Jack maybe gets a little bored, a little melancholy, so he decides to do something with the sprawling backyard. So he sections it off and builds boxes and pathways and plants a garden. It’s a pretty serious set up, very thoroughly researched - Jack sends out the soil to be tested for pH balances and nutrient composition and whatnot, and researches which plants are best for the region, and observes how many hours of sun they get, because our boy never does a thing half-assed, as we all know.
All the while he’s very quiet about it, off in his own world, and Bits watches him puttering around from the veranda as he sips his coffee and makes sure his husband doesn’t get so lost in the dirt he forgets to eat or put on more sunscreen or what have you.
Gardening books start piling up on the bedside table on top of the usual biographies, and Bits asks about it every now and again - “What exactly are you growing out there?” But Jack just shrugs and says, “Oh you know, a bit of everything.”