How Potatoes Grow

Potatoes are usually grown from other potatoes. You plant a whole, small potato, or a piece of a larger one for a new plant. The whole potato or cut piece has several slightly recessed, dormant buds or "eyes" on the surface. When conditions are right, these buds will sprout, whether the potatoes are in the ground or in a kitchen cupboard. The sprouts then develop into independent plants.

Starting From Seed
The cut potato piece or "seed" piece provides the new sprout or seedling with nourishment from its supply of stored starch.
After you've planted a seed piece, it usually takes one to two weeks for the main stem and first leaves to appear above ground. The root system develops quickly and begins to absorb nutrients as the food supply in the seed piece is used up.

Top Growth
The top, leafy part of the plant puts on a lot of growth in the first four to five weeks after planting. Then the main stem of the plant stops growing and produces a flower bud. When that happens, the plant will have as many leaves as it will ever have.
With proper sunshine, the leaves eventually produce more food than the plant needs, and the excess energy is channeled downward to be stored in the "tubers" -- thick, short, underground stems -- which we simply call potatoes. Irish potato tubers develop above the original seed piece, rather than below it like many other underground vegetables.

Storage
In general, the storage process starts five to seven weeks after planting, often when the plants have flowered. Some varieties will produce great potatoes with no flowering at all, but usually flowering is a sign that something is definitely happening underground.
Incidentally, potato flowers don't produce any nectar, so they're not visited much by bees or insects. The flowers are self-fertilized, and many potato plants produce small green seed balls about 1-inch in diameter, which contain up to 300 seeds. These seeds are mostly used by potato breeders.
When the tubers start forming, cooler temperatures are a plus. Years ago, research showed that fewer and fewer tubers were formed on the plants as the temperature went from 68o to 84oF. In fact, none formed at 84&deg F.

Best Weather
The best potato crops are produced when the daytime temperature is in the 60&deg to 65&deg F range, and when night temperatures are below 57&deg F. When the weather is hot, the top part of the plant respires heavily, reducing the amount of food material that can otherwise be put into storage in the tubers below ground. This helps to explain that while potatoes may be a summer crop up North, they're a late winter, spring or fall crop in the South.
In a big potato-producing state like Idaho, for example, cool summer days and nights keep energy losses to a minimum. Plenty of starch is stored in the tubers, helping to make the Idaho potatoes terrific, big, mealy bakers.

Best Spuds
As potatoes enlarge underground, the outside layer of the tuber gets tougher and tougher, keeping moisture within the potato and protecting it from outside attacks by organisms that can cause rot.
This toughening of the skin continues even as the plant tops die, the signal to the gardener that the harvest is at hand. Potatoes can remain underground for a little while after the tops die, so that the last energy in the tops can be transferred to the tubers. If the outer skins can't be rubbed off after the potatoes have been dug, they'll store well.

Source: http://www.garden.org/foodguide/browse/veggie/potatoes_getting_started/560

What is a Potato?

A potato is a starchy edible tuber native to South America and cultivated all over the world. The tuber has been domesticated for over 10,000 years, and over 1,000 varieties are known, although only a fraction of this number are cultivated commercially. They play an important role in the culture and history of many South American countries, and were adopted into European cuisine and culture when they were introduced in the 1600s.

Domestication of the wild potato began around 8,000 BCE. Many varieties were cultivated by native people, and the tuber quickly became a staple food, along with corn. When explorers first began to visit South America, they were introduced to potatoes, and samples of the crop traveled back to Europe with them. It was at first a reluctant introduction to the garden, as the plants are in the nightshade family, along with eggplants and tomatoes. Parts of nightshade plants can be toxic, and European farmers were at first suspicious of this food. After trial fields grew successfully, however, it was a welcome addition to the European diet.

Potatoes are somewhat difficult to grow. They are subject to rot and fungus if not cared for properly, as the Irish learned in 1845. The plants are usually propagated from buds, called eyes, which form if the tubers are left in the soil instead of being harvested. They will also bud in cool, dry storage conditions, as cooks who forget about those in storage have learned. They are often cut into pieces and replanted, although potatoes can also grow from seed, depending on the variety. As a general rule, the soil must rest between plantings. The plants prefer full sun and light, and loose soil that is watered infrequently. Once harvested, potatoes can be stored in a cool dark place for an extended period of time.

Vitamins A and C can be found in abundance in the tuber, along with some other vitamins and minerals. They can be prepared in a number of ways, but are always eaten cooked. Fried foods, such as French fries and potato pancakes, are popular in many parts of the world, but they are also baked, roasted, boiled, and stewed. The dense white flesh can be dressed with a number of condiments or eaten plain, depending on personal preference.

When seeking out potatoes in the store, shoppers should be aware that different types are more suitable for different foods than others. Waxy potatoes will retain their shape through cooking, making them good choices for boiling and frying. Starchy ones break down, and are good mashed baked.

Source: http://www.wisegeek.org/what-is-a-potato.htm