Mapping sun and shade in your own yard
Before you build a single cold frame, you need to know your own yard. Not the yard next door, not what the extension office says about "full sun" in general. Yours. Every property in this valley has its own microclimate, and once you start extending the season, six inches of shade difference matters a lot more than it used to.
Here's what actually happens. In summer, everything gets enough light and you can get away with sloppy placement. Come October, when the sun's lower and the days are shorter, the shadows off your house, your fence, and that one maple tree stretch out and start eating hours of light your beds used to get. A spot that was blazing in July can be shaded by 2pm in late September. If you're trying to squeeze extra weeks out of lettuce or spinach, that light is the whole game.
The walk-around, morning to dusk
This is the part you can't skip and can't fake from memory. Pick a Saturday (or a day off) and actually watch your yard.
- Early morning (7-8am). Note what's lit and what's still in shadow from the house or a fence line.
- Midday (noon-1pm). Most of the yard should be getting sun by now, but check the edges, near tall shrubs or a neighbor's tree that hangs over the line.
- Mid-afternoon (3-4pm). This is where people get surprised. Shadows start swinging the other direction and a bed that looked great at noon goes half-dark.
- Early evening (5-6pm), especially in September and October. This is your real test for fall extension. If a spot is still getting decent light this late in the day come autumn, that's a strong candidate for your cold frame.
Write it down. I'm serious about this part, not just "remember it later." A simple sketch of your yard with rough sun hours per bed, done once in spring and once in fall, tells you more than any general chart will. I keep mine taped up next to my frost calendar in the shed.
What you're actually looking for
You want two things for season extension: a spot that gets as much late-day sun as possible in fall, and a spot that isn't a frost trap. Cold air sinks. If you've got a low corner of the yard, or somewhere hemmed in by a fence with no airflow, that's where frost settles first and hardest, regardless of what your thermometer on the porch says. I learned this the hard way with a raised bed I put in a corner that seemed sheltered and cozy. Turned out "sheltered" also meant "where the cold pools at 4am." Lost seedlings there twice before I moved the bed six feet.
South-facing is the obvious answer for maximizing sun, and it's usually right, but don't assume it blindly. A south wall that's shaded by a tall fence in the afternoon isn't doing you any favors. Walk it and look.
Kids and the map
This is also a good excuse to get your kids involved without handing them anything sharp or heavy. Maggie and Mia like doing this with me, actually, they'll run around with a piece of chalk and mark sunny spots versus shady ones on the patio like it's a game. Lincoln's a different story. When he was three he "helped" by pulling up half a row of carrot seedlings because he thought that's what you do to plants in a garden. I replanted what I could and let the rest go. You either garden with little kids around or you put the garden on hold for about a decade, so I garden with them around and just plan for some losses. If you've got young kids, give them the light-mapping job and keep them away from the actual beds until they're a little older. Chalk and clipboards, not trowels.
Turning the map into a decision
Once you've got a rough picture of your yard, mark the two or three spots that hold the most fall light and the least frost risk. Those are your candidates for a cold frame or row cover setup, which we'll get into next.
One more thing while we're here: don't assume the spot you already use for tomatoes in July is your best spot for extending lettuce into November. Different season, different sun angle, different answer. I've moved things around more than once because I trusted last year's map instead of doing it again.
Before next time: spend one day, morning to evening, actually watching where the light falls in your yard, and sketch it out even roughly. Bring that sketch to next lesson, we'll use it when we talk through cold frame placement.