Earthing Up Potatoes: Guide for Beds and Containers

Illustration of potato grow bags and a basket of harvested vegetables

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Earthing up potatoes is the process of mounding soil or compost around the stems of growing potato plants. This essential gardening technique serves two primary purposes: it protects young shoots from late spring frosts and, more importantly, it ensures that developing tubers remain buried. When tubers are exposed to sunlight, they turn green; greening is a warning of potentially harmful glycoalkaloids, rather than chlorophyll itself being the poison. Discard green tubers. Keeping a protective soil cover helps prevent greening; piling the stems ever higher does not guarantee a bigger crop.

Table of Contents

When to start earthing up

Timing is critical to ensure you do not bury the plant too deeply too early, nor leave it exposed for too long. For most varieties, the process should begin once the shoots have reached approximately 23cm in height. At this stage, you should draw soil up around the stems to form a ridge, leaving only the top 10cm of the foliage visible above the soil line.

This process is not a one-time event. As the stems continue to grow taller, you should repeat the earthing up process several times, typically spaced a few weeks apart. The goal is to continue adding soil until the final height of the ridge reaches between 20cm and 30cm. While you will still get a crop if you are unable to earth up, check that developing tubers stay covered rather than treating the schedule as a yield guarantee.

Earthing up in garden beds

In traditional garden beds, earthing up is usually performed using a hoe or a garden fork to pull soil from the sides of the row toward the stems. This creates a raised mound or ridge along the length of the potato row.

Step-by-step process for beds

Initial mound: Once shoots are 23cm tall, use a hoe to draw soil from the gaps between rows toward the plants.
Maintaining the ridge: Every few weeks, check the height of the stems. Draw up more soil as the stems grow, leaving foliage exposed and stopping at the final ridge height.
Weed control: Use the earthing up process as an opportunity to remove weeds. Drawing soil over small weeds helps suppress them and prevents them from competing for nutrients.
Final height: Stop once the ridge is 20–30cm high.

For those practicing no-dig gardening, the process differs. Instead of drawing soil from the bed, you can shallow-plant the seed potatoes and then apply a deep layer of organic matter, such as garden compost or well-rotted manure, on top. This mulch serves the same purpose as earthing up by blocking light and protecting the tubers.

Earthing up in containers and bags

Earthing up in containers is a simpler process of “topping up” rather than mounding. Because the root zone is confined, you cannot pull soil from the sides; instead, you must add fresh material from an external source.

Container method

When planting in a container (which should be at least 30cm wide and deep), you typically start with the pot only half-full of peat-free multi-purpose compost. As the shoots appear and grow, you gradually add more compost around the base of the stems.

Continue adding compost until the level is just below the rim of the container. It is advisable to leave a small lip (approximately 5cm) at the top to prevent water from overflowing during irrigation. This method is particularly effective for early varieties, which are smaller and mature more quickly, making them ideal for pots, sacks, or repurposed compost bags (provided drainage holes are pierced in the bottom).

Distinctions between variety requirements

While the mechanical process of earthing up is similar across varieties, the scale and duration can differ between early and maincrop potatoes.

Early varieties (First and Second Earlies)

Early varieties are often grown in containers or smaller plots. They grow faster and are harvested by midsummer. Because they produce smaller tubers and have a shorter growing window, the earthing up process is typically shorter and requires less total soil volume.

Maincrop varieties

Maincrop potatoes stay in the ground longer, often until late summer or autumn. They produce larger individual tubers and a larger overall harvest. Maintain the ridge and repair cracks or washed-away soil for as long as tubers remain in the ground.

Diagnosis: Identifying the need for earthing up

Gardeners can diagnose whether their plants require more earthing up by observing the following signs:

Visible Tubers: If tubers are showing at the surface, cover them without disturbing the roots.
Green Skin: If the tubers are already showing green patches, they have been exposed to light. Discard green potatoes rather than simply trimming the green skin. Adding soil can protect other developing tubers, but does not make an already green potato safe.
Stem Exposure: During early growth, add soil gradually as needed; do not keep burying established foliage after the ridge or container is full.
Windrock: In very tall plants, if the stems are leaning or loosening in the soil, earthing up can provide additional structural support to the base of the plant.

Useful products for this job

The links below open Amazon UK product searches. Check the exact item, seller, current price and compatibility before buying.

Garden hoe: Used to draw soil from the sides of the row toward the potato stems in garden beds. Ensure the blade width is appropriate for your row spacing to avoid damaging adjacent plants. Search Amazon for Garden hoe.
Peat-free multi-purpose compost: The primary material used for topping up potatoes grown in containers or bags. Verify it is a multi-purpose variety suitable for root vegetables. Search Amazon for Peat-free multi-purpose compost.

Related garden guides

Sources and further guidance

Guidance researched in September 2026. The feature image is an AI-generated illustration. Product guidance is based on published information, not hands-on testing.