When to Hill Potatoes

Start when stems are about a foot tall, then hill once or twice more — finish before plants get too large to work.

Hilling is timed to plant height — not an arbitrary calendar date.

First hilling

UMN Extension: begin when stems are about a foot tall, then hill once or twice more during the season. By the end you typically have about 6–8 inches of soil pulled up along the row.

Maryland describes hilling when tops are fully growing, keeping finished hills about 6 inches above grade so tubers stay covered.

Later hillings

Repeat as stems elongate and before the canopy makes cultivation awkward. Penn State notes hilling should be completed before plants start to bloom in many production systems — a useful cue for home gardens too: do not wait until the row is an impenetrable thicket.

Why timing matters

Too early: tiny shoots can be buried clumsily or damaged
Too late: roots spread into the aisle; deep cultivation hurts plants; tubers may already be greening at the surface

Special cases

Containers / bags: “hill” by adding mix whenever stems gain several inches
Straw method: add mulch depth instead of soil

How to do it → How to Hill Potatoes