Growing Potatoes

How Potatoes are Grown

Potatoes are annual plants, meaning each year they are planted in the spring and harvested in the fall. Potatoes grow underground on a special stem called a ‘stolon.’ The potato stems above ground have attractive but non-edible flowers. Since the ‘root’ of the potato plant is not really a root but a stem, potatoes are also considered tubers.

Seed Potatoes

Large potato crops are not planted with seedlings each year. Instead, what is planted into the ground are ‘seed potatoes’ (potatoes that have hardened roots growing from them). These seed potatoes are cut into the desired size and planted in fields by special machinery. Farmers prefer seed potatoes of the same size to maximize the amount of potatoes created in a field.
The planting season in Ontario runs largely through the months of April and May. Many farmers in Ontario use potato planting machines that are guided by high-tech laser sensors to keep the rows straight and seed potatoes planted uniformly. These sensors help the farmer plant the rows with just the right distance between them, in order to maximize the yield and quality of the potato.

About two to six weeks after planting, depending on the time of year and their location, potato plants will begin to rise from the ground. A potato field needs to be kept hydrated at all times. In Ontario, over half of the crop is irrigated, meaning it is watered with large, automated sprinklers rather than just relying on rain fall. Potatoes can survive drought but do not produce as many potatoes if they do survive.

As the season progresses, growers must ensure that crops are obtaining enough food from the soil. To determine this, they test samples from growing potato plants and measure the nutrient content. If nutrient levels are low, they fertilize the crops, adding more food. 


The harvesting season begins in July and runs through the fall. The harvesting machines have a big responsibility – they need to dig the potatoes out of the ground and separate them from stems, dirt and rock, all without bruising the crop during the process.


Unlike many other vegetables, potatoes can be stored for up to 11 months in temperature-controlled environments until they are ready for packaging and shipping. About one-third of the Ontario crop is sent directly to market, with the remaining two-thirds put into storage for sale throughout the year.

Grading and Packaging

Potatoes are graded and packaged according to federal and provincial standards. The grades and grade names for potatoes are Canada No. 1, Canada No. 2, Ontario No. 1, Ontario No. 2, and Ontario Mini. All potatoes sold in Ontario must be properly packed to the grade standards and marked accordingly.

The grades for potatoes are based on uniformity of size and shape, minimum and maximum size, color, maturity, freedom from disease, injury and other defects and damage and cleanliness.


Potatoes are generally sold to the consumer in 5-lb and 10-lb bags or sold in bulk quantities. Recently, some stores have started selling a 7-lb bag. All packages must meet grade and label specification and provide information about the variety of the potato, the quantity, the name and address of the packer and the country of origin.