Row Orientation Math: Which Way Should Your Rows Run?

The short version: north-south rows spread sunlight evenly across a full day, while east-west rows shade themselves — and exactly how much that costs you depends on the sun's angle at your latitude, which swings from about 73 degrees at summer solstice to 27 degrees at winter solstice at 40 degrees latitude.

Row orientation gets treated as a minor detail, but the physics behind it is straightforward trigonometry: the sun's path across the sky determines which row direction casts the least shade on itself. Get it backward and you can lose a meaningful percentage of a tall crop's light exposure without ever noticing the cause.

Why Orientation Affects Light

The sun tracks east to west through the sky, rising in the east and setting in the west, reaching its highest point (solar noon) somewhere near due south for most of the Northern Hemisphere. Rows running north-south let sunlight sweep across both sides of each row over the course of a day, since the sun is on the east side of the row in the morning and the west side in the afternoon — both sides get roughly even total exposure. Rows running east-west have one side facing the sun's higher midday arc and the other side more often in shade, particularly for tall plants whose height casts a longer shadow onto the row behind them.

The Angle That Matters: Solar Elevation

How much this matters depends on the sun's elevation angle at midday, which changes with your latitude and the season. At 40 degrees latitude (roughly the parallel running through Denver, Philadelphia, and Beijing), the sun's midday elevation is about 73 degrees at summer solstice and drops to about 27 degrees at winter solstice. A higher angle means shadows are shorter and land closer to the plant's own base, so east-west row shading matters less in summer. A lower angle means shadows stretch out much further, so east-west row shading matters far more in the shoulder seasons and winter.

A Worked Shadow Comparison

A corn row 6 feet tall at a 27-degree sun angle casts a shadow roughly 6 divided by the tangent of 27 degrees, or 6 divided by 0.51, about 11.8 feet long. The same row at a 73-degree summer sun angle casts a shadow of 6 divided by the tangent of 73 degrees, or 6 divided by 3.27, about 1.8 feet. That's a shadow more than six times longer in winter-angle sun than summer-angle sun from the identical row.

When North-South Wins

For most home vegetable gardens planting through spring, summer, and into early fall, north-south row orientation gives more even light across the growing season, especially for tall crops like corn, staked tomatoes, and trellised beans or peas, where row-to-row shading is the main risk. If you have flexibility in how your rows run, default to north-south unless another factor overrides it.

When Slope Overrides Sun Angle

On sloped ground, erosion control usually outranks light optimization. Rows running straight down a slope funnel water and cause soil to wash away with every rain; rows running across a slope (on contour) slow water down and let it soak in instead of running off. If your slope's natural contour happens to run east-west, that erosion benefit is usually worth accepting some extra row shading, particularly since you can partially compensate by widening row spacing on the shaded side.

Short Crops Care Less

The entire orientation question matters most for tall crops, because shadow length scales with plant height. Low-growing crops like lettuce, strawberries, or most root vegetables cast short shadows regardless of sun angle or row direction, so their orientation can be set by other factors — access paths, irrigation line runs, or simply matching the orientation of taller crops nearby — without a meaningful light-exposure penalty either way.

Which Way Should You Actually Run Your Rows?

Row orientation comes down to one calculation: how long is the shadow your tallest crop casts, at your latitude, during the months it matters most. North-south rows average that shadow evenly across a day; east-west rows concentrate it on one side. Default to north-south for tall crops, but let slope and erosion control override that default when the two conflict.