Growing potatoes in containers is a popular and convenient method for gardeners with limited space. Knowing the correct time to harvest is important for maximizing both the total yield and the flavor profile. Proper timing is determined by visual cues from the plant and depends on whether the goal is to harvest tender, small potatoes for immediate use or mature, thick-skinned potatoes for long-term storage.
Reading the Visual Cues for Harvest Timing
Harvest timing relies heavily on the plant’s above-ground foliage, which signals the developmental stage of the tubers below. “New potatoes” are small, thin-skinned, and have a fresh, mild flavor. They are ready approximately two to three weeks after the plant begins to flower, while the foliage is still green and vigorous. Since they lack a firm skin, new potatoes must be consumed quickly and will not store well.
For long-term storage, the tubers must fully mature and “set” their skins. The plant’s foliage must be allowed to naturally yellow, wither, and completely die down (senescence). This dieback signals that the plant has stopped channeling energy to the leaves. Once the foliage is fully dead, leave the tubers in the container for an additional ten days to two weeks to promote skin set.
Skin set is the natural hardening of the periderm, the potato’s outer layer, which thickens and adheres tightly to the flesh. This protects the tuber from moisture loss and potential pathogens during storage. To check for proper skin set, gently rub the skin of a test potato; if the skin easily rubs off or “slips,” the potatoes are not ready for storage. Stopping watering two weeks before the planned harvest also assists this process by allowing the growing medium to dry out, which encourages the skin to toughen.
The Process of Harvesting Potatoes from Containers
The container method simplifies the physical removal of the tubers compared to digging in the ground. About a week before harvesting storage potatoes, stop watering the container completely to ensure the growing medium is dry. This minimizes the risk of rot. Harvesting begins by preparing a clean, flat surface, such as a tarp or wheelbarrow, to receive the container’s contents.
The entire container can then be carefully tipped onto the prepared surface, spilling out the growing medium and the potato tubers. This method is gentler than using a garden fork, which commonly results in piercing or slicing the potatoes. Next, sift through the loose soil or compost mixture by hand to locate all the hidden tubers.
Handle the newly exposed potatoes with care, avoiding excessive scrubbing or rough treatment that could bruise or damage the skin. Damage creates an entry point for disease and significantly reduces storage life. After collection, gently brush the tubers to remove large clumps of clinging medium, but do not wash them.
Preparing Potatoes for Long-Term Storage
Following harvest, potatoes require a post-harvest treatment called “curing” to prepare them for extended storage. Curing is a period where the skin heals minor abrasions and strengthens the periderm. This process is best done in a dark, well-ventilated space, maintaining a temperature between 50°F and 55°F and a high relative humidity, ideally 95%.
The potatoes should be spread out in a single layer on a surface like a wire rack or newspaper, ensuring they are not exposed to light. Curing typically takes seven to fourteen days, allowing damaged areas to suberize, or form a cork-like seal. Avoiding washing the potatoes is important because surface moisture can promote the growth of pathogens during curing and storage.
Before moving the cured potatoes to their final storage location, inspect them. Any tubers with signs of damage, disease, or greening should be set aside for immediate consumption. Greening indicates the presence of solanine, a mild toxin that develops when potatoes are exposed to light. For long-term storage, the ideal environment is a cool, dark, and dry location, with temperatures lowered to 40°F to 45°F to slow down metabolic processes.