How to Earth Up/Hill Potatoes (and Why)

Earthing up, also known as “hilling,” is a classic potato-growing technique that means regularly piling up soil or mulch around sprouts as they grow. This easy process dramatically boosts yields, keeps potatoes from greening, and provides protection from pests and frost.

Why Earth Up Your Potatoes?

• Prevents Green Potatoes: Sunlight on tubers produces solanine, turning potatoes green and bitter (and mildly toxic).
• Increases Yield: Each time you earth up, you encourage more tubers to form along the buried stems.
• Frost Protection: Extra soil insulates young shoots against surprise spring frosts.
• Discourages Weeds: Frequent hilling buries weed seedlings as they emerge.

When and How to Earth Up

1. First Earthing:
   When shoots reach 15–20cm (6–8 in) tall, begin your first hilling.
2. Process:
   • Use a hoe, rake, or your hands to pull soil from between rows or from the edge of a container over the potato stems.
   • Cover all but the top few leaves.
3. Repeat:
   Continue every 2–3 weeks, or whenever another 10–15cm (4–6 in) of new stem has grown, until you’ve created a mound 20–30cm (8–12 in) high.
4. In Containers/Grow Bags:
   Simply add more compost or mulch to cover stems each time they reach above the surface.

Tips for Easiest Earthing Up

• Don’t Cover All Leaves: Always leave the top leaves exposed so the plant can photosynthesize.
• Mulch Alternative: Straw, grass clippings, or leaf mold can be used in place of soil, especially in raised beds and containers.
• Final Hill: Stop earthing up once the plants flower or the hill is as tall as your container allows.

What If You Don’t Hill Up?

• Exposed tubers turn green and become inedible.
• Yields are likely to be lower, especially in light soils or containers.