How Deep to Plant Potatoes (And Why Hilling Matters More)

The short answer is four inches. The longer answer is that planting depth matters much less than what you do afterwards — because a potato plant does not make its crop at the depth you planted it.

Why four inches, not eight

It is tempting to plant deep once and skip the hilling. It does not work well, for two reasons.

Cold soil. Spring soil warms from the top down. At 4 inches the tuber is in soil that is warming; at 10 inches it sits in cold, wet ground, and a seed potato that sits rather than sprouts is a seed potato that rots.

Stem, not seed. Tubers form on stolons — underground stems — that grow out of the stem tissue, in darkness. The seed potato itself just provides the starting energy. So the useful variable is not how deep the seed went, it is how much stem ends up buried, and hilling is how you control that after the plant is already growing strongly.

Spacing

12 inches apart for maincrop, 10 inches for earlies, and 30–36 inches between rows — you need that row width as a soil supply for hilling.

Tighter spacing does not mean more potatoes; it means the same weight divided into more, smaller tubers, and below about 8 inches the total yield actually falls. Wider spacing gives you fewer, bigger bakers.

Hilling, step by step

First hill when the shoots are 6–8 inches tall. Draw soil up around the stems from both sides, leaving the top few inches of foliage showing. Yes, you are burying most of the plant. It is fine.

Repeat every two or three weeks until the mound stands 8–12 inches above the original soil line, or until the plants flower.

Straw, compost, grass clippings, or leaf mould all work as well as soil and are lighter to move.

Containers

Start with 4–6 inches of mix in the bottom of the bag, set the seed potato on it, cover with 4 inches, and top up as the shoots grow until the container is nearly full. That is hilling by another name.

Sizing: a 10-gallon bag takes one or two seed potatoes. Four in the same bag gives you a bag of marbles. Containers also dry out fast, and potatoes are thirsty while tubers are sizing — inconsistent watering is what causes hollow heart and knobbly, cracked tubers.

Before any of that: chit them

Stand the seed potatoes eyes-up in a tray somewhere cool and light for two to four weeks. Short, stubby, dark green shoots are what you want; long pale ones mean too warm and too dark.

Chitting buys a couple of weeks on the season, which matters most for early varieties.

Cut anything larger than a hen’s egg into pieces with at least two eyes each, and leave the cut faces to callus for two or three days before planting. A fresh wet cut in cold soil is an open invitation to rot.

And use certified seed potatoes. Supermarket potatoes are often sprout-inhibited, and more importantly they carry no assurance against the viruses and blight strains that certification exists to keep out of your soil.