Hilling, or mounding, is a fundamental technique for cultivating a successful potato harvest. This practice involves systematically piling soil or organic material around the base of the growing potato plant. Hilling supports plant structure and directly influences both the quality and quantity of the final yield. Mastering the timing of this process ensures an abundant bounty of edible potatoes.
Why Hilling Potatoes is Crucial
The purpose of hilling is twofold: supporting the plant’s growth habit and addressing a food safety concern. Potato tubers are specialized underground stems that develop on stolons extending from the buried part of the plant. Adding material around the base increases the surface area on the stem where these stolons can form, encouraging the production of more potatoes. Hilling also prevents developing tubers from being exposed to sunlight. Exposure causes the potatoes to turn green as they produce chlorophyll and solanine, a naturally occurring toxin that can cause sickness if consumed.
Initial Hilling: Recognizing the Right Time
The first hilling is the most important action, setting the stage for productive growth. The ideal time to begin is when the potato stems are approximately 6 to 8 inches (15 to 20 centimeters) tall. Starting too late restricts the total length of the stem available for tuber development, limiting the overall yield potential.
To perform the first mound, use a hoe or rake to gently draw loose soil up and around the base of the plant. The goal is to bury a significant portion of the stem, leaving only the top 2 to 3 inches of green foliage exposed. This action anchors the young plant and forces the lower stem tissues to produce stolons. The initial mound should be substantial, forming a ridge that is 3 to 6 inches high.
Maintaining the Mound: Subsequent Hilling and Completion
Following the initial effort, hilling becomes a continuous maintenance task throughout the early and middle stages of the plant’s life. Repeat subsequent hilling every two to three weeks, or whenever new growth extends another 6 to 8 inches above the existing ridge. Growers can use garden soil, aged compost, or loose organic materials like straw or shredded leaves. Using lighter materials such as straw provides coverage and insulation while making the final harvest easier.
The hilling process is finished when the plant begins to show signs of maturity, typically when it starts to flower heavily. Tuber initiation, the period when the number of potatoes is determined, often coincides with the flowering stage. Once the plants are flowering or the foliage covers the ground, hilling is no longer necessary. The mound should have reached a total height of 10 to 12 inches to protect all developing tubers from light exposure.