What Is Skin Set On Potatoes?  

Many home gardeners enjoy growing potatoes and storing them for winter use. Potatoes are both nutritional and versatile, providing the makings for many recipes. To enjoy the fruits of your labor all year long, you will need to make sure your potatoes have a good skin set and have been appropriately cured before winter storage.

What is meant by skin set when growing potatoes?

The skin, called the periderm, is the outer casing of a potato that serves to conserve moisture and protect the growing tuber from the invasion of diseases and insect pests. The periderm grows and expands as the tuber grows and does not stop growing until the potato tuber has matured (or stopped growing). During this stage, the skin slips from the potato tuber easily as it does not adhere tightly to the tuber.

When the tuber stops growing, the skin binds with the underlying tissue giving the potato a tough outer skin in a process called skin set. A skin set is necessary to protect the tuber from disease and moisture loss during storage. Potatoes with good skin set can be harvested with little damage to the tuber, whereas before skin set occurs, the skin will slip easily from the tuber resulting in bruises and cuts on the surface of the potato.

When does skin set occur?

Skin-set occurs naturally when the tops of your potatoes die back, and the potatoes stop growing. Many farmers use herbicide spray to kill the foliage in preparation for harvest. In the home garden, you can either wait for the foliage to die naturally, use a herbicide, or cut the tops from the potatoes to encourage skin set before harvesting.

This should be done in the fall when the potatoes have reached their mature size. If you aren’t sure when your potatoes are ready for harvesting, refer to the days to maturity of your particular cultivar.

Potatoes typically require 90 to 120 days from the date of planting them before they are ready for harvest. Potato varieties are classified as early, mid-season, and late-season potatoes and mature at different times.

  • Early Season potatoes mature in approximately 75 days.
  • Mid-season potatoes mature in 90 to 100 days.
  • Late Season varieties mature in 110 days or more.

How long does it take to fully set the skin?

The amount of time it takes for a skin set to occur depends on several factors. Skin-set may occur in as little as ten days but may take up to three weeks.

  • Some varieties of potatoes, such as Red Pontiac or Red Norland, take longer for skin set to occur, while others, like Russets, mature quicker.
  • Potatoes that receive too much nitrogen and potassium may take longer for the vines to mature and result in it later skin set, says Growing Produce.
  • Wet weather after the vines die back can also contribute to poor or delayed skin set.

Do I need to skin set new potatoes?

The skin set protects the potato tuber from moisture loss, disease susceptibility, and insect pests. It is necessary for the long-term storage of potatoes. However, a skin set is unnecessary if you are eating the potatoes right away, such as when harvesting and eating new potatoes.

When is good skin set very important?

A skin set is essential for any potatoes that you intend to store for the winter as it protects the potatoes from moisture loss and aids in resisting diseases. Without a skin set, your potatoes cannot be kept for more than a few weeks and will lose moisture and flavor. Moisture loss causes potatoes to soften and shrivel and changes the texture of the potato.

The skin set is not essential if you intend to harvest potatoes and eat them within a few days. Many gardeners prefer tender new potatoes whose skins slip from the tuber easily. New potatoes can be cooked and eaten with the skin, or you can scrub them with a vegetable brush to remove the tender skins before cooking them.

A young potato which has not yet set its skin
This young potato has not yet set its skin – notice the skin on top peeled back slightly by rubbing with a thumb.

Is skin set the same as curing?

No, curing is the process of air drying which is done after harvesting the potatoes to thicken the skins further and get them ready for storage. Curing ensures the outer layer of the potatoes dries thoroughly, which heals any nicks, cuts, or bruises from harvesting. Potatoes should never be put into long-term storage wet or damp as disease and rot escalate quickly.

To cure your potatoes, place them in a cool, dark, well-ventilated area with a relative humidity between 85 and 95 percent for two weeks. Examine the cured potatoes for bruises or nicks that did not heal or any signs of damage, such as soft spots. Either eat these potatoes right away or discard them before putting the rest of your potatoes into winter storage.

Related Questions

Do you need to peel potatoes before cooking them?

The skins of new potatoes are thin and can be rubbed from the tuber easily. Many cook new potatoes in their skins and either slip them from the skin before eating or eat the potato skin and all.

However, when potatoes mature, and skin set occurs, the outer skin becomes tough. With the exception of baked potatoes which are cooked in the skin, mature potatoes should be peeled before cooking. The skins of mature potatoes won’t hurt you, but they are not very palatable.

Can you eat potatoes with green skins?

Potatoes with green spots from exposure to the sun (or artificial light) must be peeled, and any green flesh must be cut away before cooking and eating them. Light exposure causes the skin (and sometimes the underlying flesh) to turn green from chlorophyll, often accompanied by the toxic enzyme solanine.

Solanine, also found in the foliage, buds, and sprouts of potatoes can lead to gastric upset. In severe cases, when large amounts of solanine are consumed, it can lead to solanine poisoning. Dispose of peelings from green potatoes in a composter in an area out of reach of small children and pets to avoid accidental ingestion.

Summary

A good skin set is vital to the long-term storage of potatoes as it protects the tubers from moisture loss and makes them more resistant to disease and insect pests. However, a skin set is not a concern if you are harvesting and cooking your potatoes right away. The lack of skin set does not affect freshly harvested potatoes’ flavor, texture, or nutritional value.