How to Hill Potatoes

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How to hill potatoes is a simple job with one clear rule: pull loose soil up around the stems once the plants are about six inches tall, then repeat it every couple of weeks until the mound is 6 to 8 inches high. Hilling keeps developing tubers covered, which helps control weeds and keeps the tubers from turning green.

The pages we opened agree on the method but not on every number. This guide covers planting so the hill has room, when to start, how to build the mound, and what the pages leave open.

Quick answer

Start hilling when the plants are about six inches tall. One Montana guide starts later, at eight inches.
Use a hoe to pull soil from between the rows and mound it around the base of the plant, adding a new layer of about two inches each time.
Repeat every couple of weeks until the hill is 6 to 8 inches high. The University of Maine bulletin says up to three hillings may be needed.
Keep tubers covered so they do not turn green, and keep the soil evenly moist.

Plant so the hill has room to form

Planting comes first, and the rows set the room the mound will need. The University of Maine bulletin gives a clear planting method: “Make a furrow four to six inches deep, and, after fertilization, place seed in the furrow and cover with two inches of soil.” It also gives the spacing: “Seed spacing ranges from eight to 12 inches within the row and 30 to 36 inches between rows.”

The Washington State guide uses a similar layout with different figures. It says, “To plant, use a hoe to create furrows (shallow trenches) about 4 inches deep.” It also says, “Plant seed potatoes 10-12 inches apart in rows spaced 24-36 inches apart.” It also says, “Furrows should be spaced 2 to 3 feet apart.”

The Montana guide takes a different route. It digs a trench about 6 inches deep, places the seed pieces in the bottom, covers them with soil, and fills in the rest of the trench as the potatoes emerge. Whichever method you use, the goal is the same: enough loose soil around the stems to build a mound later.

Drainage matters before any hilling starts. The Maine bulletin says, “Potatoes do best in fertile, well-drained soils.” It adds that “Soils that are poorly drained tend to produce poorly shaped potatoes and tuber rot.” The Montana guide says to “Till the soil as deeply as possible to encourage good drainage.” The Maine bulletin also says potatoes “prefer slightly acidic soils” and gives a typical range: “a soil pH of 5.3 to 6.0 is typical for potato production.”

Watering starts later than planting. The Washington State guide says, “Unless the soil is very dry, do not water your potato planting before plants emerge because it can lead to seed rot and crop failure.” Hold off until the shoots appear, unless the soil is dry.

Know when to start hilling

The main cue is plant height. The Maine bulletin says, “Once the plants are about six inches tall, they should be hilled.” The Washington State guide uses the same six-inch starting point. The Montana guide starts later, when the stems are about 8 inches high, and then hills twice more at two-week intervals.

The guides differ by two inches on the first hilling, and they do not explain the gap. Six inches is the earlier figure and eight inches is the later one. This guide shows both, so you can match the cue to how your plants are growing rather than to a calendar date.

Build the mound one layer at a time

The Washington State guide describes the motion in detail. “When hilling, wait for potato plants to reach a height of 6 inches or more, then use a hoe to gently pull soil from between the rows and gently mound it around the base of the plant, creating a new 2-inch layer of soil.” Each pass adds a thin layer rather than one big pile.

The Montana guide describes the same job with soil brought from both sides of the row. The Maine bulletin calls the result a mound: “Simply form a mound above the potato row.” Work from both sides, as the Montana guide describes.

Plan on more than one pass. The Maine bulletin says, “Up to three hillings may be needed to build a potato hill, depending on conditions.” The Montana guide says to “Hill two more times at two-week intervals.” The Washington State guide repeats the job “every couple of weeks until the” hill is 6 to 8 inches high.

Use a hoe, and mind the roots

A hoe is the tool all three guides assume. The Maine bulletin notes that “Cultivation during hilling controls weeds between the potato rows; hand pulling can eliminate the remaining weeds.” It adds that “Early weed control is essential for good potato yields.” Cultivation covers the weeds between the rows, and hand pulling handles what is left.

A tiller is a different case. The Maine bulletin says, “Tilling will help control weeds between the potato rows.” It then warns, “But if you’re using a garden tiller, be careful you don’t damage potato roots and stolons.” A tiller needs care near the plants. The Montana guide keeps its weed advice short: “Hoeing should take care of emerged weeds.”

Keep tubers covered and out of the light

The main reason to hill is light. The Washington State guide says, “Greening occurs when tubers are exposed to sunlight.” It also says, “Hilling potato plants helps control weeds, loosen the soil, and prevent tubers from turning green.” Soil, or straw where you use it, keeps the tubers in the dark while they form.

The same guide explains the risk. It says that “the tubers also develop a poisonous alkaloid (solanine) when exposed to light.” The Ask Extension expert calls hilling “The most common and necessary practice when growing potatoes is hilling.” That expert also reports finding no information on a controversy about it.

Water evenly while the hill forms

The Washington State guide gives a rough amount: “After the plants emerge, potatoes need about 2 inches of water per week, depending on the weather and the type of soil.” The same guide says, “When irrigating, moisten the top 18 inches of soil.” Additional water is not needed because potato roots only grow to a depth of 18 inches in good soil.

The Montana guide asks for steady moisture: “Keep potatoes evenly moist but not too wet.” It links even moisture to the tubers themselves: “Maintaining even moisture as the tubers form will reduce the development of scab.” The Washington State guide makes the same point in its own words, saying that “maintaining an even soil moisture is crucial to producing a good crop of well-shaped potatoes.”

Feed at the second hilling

The Montana guide ties fertilizer to the hills. “At the second hilling, side-dress with compost, or a small amount of granular fertilizer.” In that schedule, the second hilling comes two weeks after the first. For a related question about compost in raised beds, see our post on compost for raised garden beds.

The Maine bulletin takes a firmer line on one input. “Manure is not recommended on potatoes.” The Montana guide is more open: “Manure can be used, but it often promotes the development of a disease called scab.” The two guides disagree, and this draft does not settle the question. If you follow the Maine advice, leave manure out of the hill, and use the compost or granular feed the Montana guide names for the second hilling.

Hill in straw, trenches, or containers when soil is hard to work

Straw is one option. The Washington State guide says, “Growing potatoes under straw is an alternative to hilling them with soil.” It describes the routine: “When growing potatoes under straw, wait for potato sprouts to appear above the straw, then add another 6-inch layer of straw.” Add each new layer when sprouts show above the straw, as the guide describes.

The Ask Extension expert adds that “Soil, compost, and straw can be used to hill potatoes.” The same reply lists other forms: a trench, a raised garden box, a large pot, or a fabric garden bag. The reply gives no sizes for those forms. For other crops that suit raised beds, see our post on vegetables to plant in raised beds.

Mistakes to avoid

Stopping at a shallow mound. The Washington State guide aims for a 6 to 8 inch hill, so a low ridge gives less cover than the guide describes.
Leaving tubers exposed. The Washington State guide says greening occurs when tubers are exposed to sunlight.
Working wet soil. The Maine bulletin says poorly drained soils tend to produce poorly shaped potatoes and tuber rot.
Digging too close with a tiller. The Maine bulletin warns against damaging potato roots and stolons.
Letting weeds take over. The Maine bulletin says early weed control is essential for good potato yields.
Adding manure. The Maine bulletin says manure is not recommended on potatoes.

Frequently asked questions

How tall should potato plants be before hilling?

About six inches, according to the Maine bulletin and the Washington State guide. The Montana guide starts when the stems are about 8 inches high. The pages do not say why the two figures differ, so the choice is yours to make by looking at the plants.

How many times should you hill potatoes?

It depends on the guide. The Maine bulletin says up to three hillings may be needed. The Montana guide says to hill two more times at two-week intervals. The Washington State guide repeats the job every couple of weeks until the hill is 6 to 8 inches high.

Can you hill potatoes with straw instead of soil?

Yes, according to the Washington State guide, which calls growing under straw an alternative to hilling with soil. The Ask Extension expert says soil, compost, and straw can all be used to hill potatoes.

Is hilling really necessary?

The Ask Extension reply, written for a reader who had heard about a debate, says the expert found no information on a controversy. The reply calls hilling a standard practice. The sources do not give a yield comparison between hilled and unhilled plants, so this guide does not claim one.

What happens if potato tubers turn green?

The Washington State guide says greening occurs when tubers are exposed to sunlight, and that light-exposed tubers develop solanine. Keep tubers covered with soil or straw, which is the point of hilling in the first place.

Harvest and storage notes

The Montana guide says new potatoes can be ready after about 60 to 70 days, and it suggests digging around the edges of the plant with a fork to take a few tubers and check their size. If the tops have not died, the Maine bulletin says to pull them off or cut them off at least seven days before harvest. Store the crop in a cool dark place, and not in a refrigerator, as the Montana guide advises.

Bottom line

Start hilling when the plants are about six inches tall, build the mound from both sides of the row, and repeat every couple of weeks until the hill is 6 to 8 inches high. Keep the tubers covered, keep the soil evenly moist, and leave manure out of the hill.

How we chose

This guide draws on university extension pages about home-garden potatoes and one expert reply from an extension question service. We opened four pages with curl on 2026-10-23 and kept only statements that appear word for word in the fetched text, paraphrasing the rest. Two pages, from Georgia and Minnesota, returned HTTP 403. An Iowa State page gave no response, and a Michigan State PDF returned a bot-check page with no article text. None of those is counted. Where the pages disagree on the first hilling height, the guide shows both figures.

What we could not verify

The pages cover hilling in general. The gaps below are points they leave open.

What the sources do not say

Why the first hilling height is six inches in two guides and eight inches in the third.
A yield figure for hilling. None of the pages we opened gives one.
Whether manure belongs in the hill. The Maine and Montana guides disagree on it.
Sizes for hilling in trenches, raised boxes, large pots or fabric bags. The Ask Extension reply names those forms without measurements.
A date to stop hilling. The pages give a final mound height, not a calendar date.
Timing for any one region. The guides come from different states, so planting and hilling dates differ. Check your county extension for local timing.
Pest and disease treatment. The Maine bulletin names products for those problems. This guide gives no treatment advice.

Sources

https://extension.umaine.edu/publications/2077e/ (opened 2026-10-23)
https://pubs.extension.wsu.edu/product/growing-potatoes-in-home-gardens-home-garden-series/ (opened 2026-10-23)
https://www.montana.edu/extension/valley/potatoguide.html (opened 2026-10-23)
https://ask.extension.org/kb/faq.php?id=872058 (opened 2026-10-23)