Have we lost the art of growing potatoes? At one time, every garden had a potato plot where it was the pleasant summer chore to go out from time to time and do the hilling and weeding. There was no room for impractical plants such as flowers, and even peas were considered a luxury. Some ambitious gardeners from the “old country” would even grow potatoes on the boulevard in front of their houses to increase their yields.
Today, you can grow potatoes in very small spaces, including in bags that are commercially sold for just this purpose. Not only does this solve the space problem, but it ensures constant rotation so that there is no chance of pathogen buildup in the soil the spuds are planted in because you will change the soil annually.
The secret to this “new” technology is found in understanding the needs of the plant and how it grows.
How potatoes grow
Potatoes, Solanum tuberosum, like their cousins tomatoes, are deep-rooted plants that need a consistently moist, but not soggy, soil to grow in. They prefer soil that is on the acidic side – a pH of 5 to 5.5. Potato scab may result from alkaline soils, and you should never use lime in the potato patch.
Potatoes send out two kinds of roots; true roots that reach down deep into the soil for nutrition and water and rhizomes or underground stems that stay closer to the surface and upon which are formed little nodes of starchy material – potatoes, that are storage plants for new growth.
Potatoes also produce an above ground fruit, the true seeds, which are non-edible, but from which new potatoes can be grown by the dedicated gardener.
Most home-grown potatoes, however, are started from existing stock – even those purchased for consumption from the local supermarket can be used. These are called seed potatoes. It’s a good idea to use new stock each year to avoid disease. You can also purchase seed potatoes from nurseries.
The first step is to get the potatoes to sprout, which they will normally do under the right conditions in spring in a cool dark space, including in the ground. The sprouting potato can be planted whole or cut into two or three pieces, each one containing two to three “eyes” from which the sprouts emerge.
One method is to plant your seed potatoes into the ground by preparing an eight to ten inch deep trench and covering the seed potatoes with about four inches of soil, and then topping up the soil from the ridges alongside your trenches as the plant emerges. This avoids the possibility of damaging roots by having to dig between rows of potatoes for hilling purposes.
You can also grow them in containers by placing seed potatoes in a shallow layer of about four to six inches of soil and covering them with another four inches of soil. You will continue to add soil as the plant grows.
It takes two to three weeks for the planted seed potatoes to produce a main stem and leaves that appear above ground. For the first four to five weeks after that, most of the energy of the plant goes into producing this top growth. You can continue to add soil as the stem grows.
Once the plants have flowered, they will begin to produce the potatoes on their lateral rhizomes. It is now critical that you add soil or “hill” the potatoes to avoid letting any light reach the newly formed tubers. Exposure to light can cause the potatoes to produce solanine and chlorophyll (green potatoes). This makes them bitter and inedible and if you eat enough solanine, it could cause nausea, headache and even death. Hilling also encourages additional potato productions, increasing yields.
Nor does the hilling process have to include soil. Some people hill with thick layers of straw to keep the product dirt free.
Harvest can be a two-pronged thing, where you remove baby potatoes shortly after blooming and leave some to grow into larger spuds, to be harvested when the plant dies back.
Potatoes are sensitive to temperature and should not be planted out before the soil reaches 7 degrees C (45 F). They grow best when the soil is between 15.5 degree C (60 F) to 18.3 degrees C (65 F). Studies have shown that few potatoes are produced between 20 degrees C (68 F) and 29 degrees C (84 F) and production stops completely when soil temperatures rise above 29 degrees C.