How Potatoes Grow, Step-by-Step

Posted on: November 8th, 2011 by Annette Welsford 2 Comments
If you have never grown potatoes before, it is a good idea to familiarise yourself with the growing process of tubers, so that you can take appropriate and progressive action to ensure a successful crop.
 
While stems, leaves and flowers do form above the ground, it is the expanding section of the plant – the tuber – under the ground that forms the crop.
 
Once you have planted your "seed" tubers, there are five main stages to watch for:
  • the green sprouts that emerge from the eyes of the seed potatoes,
  • the stalks and lush green leaves that form,
  • flowers (and tubers),
  • healthy plants,
  • the plants start to turn yellow and lose their leaves.
The Buds Sprout
You may be able to buy seed potatoes from a wholesale stockist in your area, alternatively, you are going to have to produce your own seed potatoes from good quality potatoes bought at your local vegetable shop or supermarket. Do not be tempted to try and grow anything that you might be put off from eating; for example tubers with nematodes or skin blemishes, however minor.
 
If you choose the latter route, a good way to encourage them to sprout is to lay them out in trays until they shoot. In the UK they call this "greening", and it is considered to be an excellent way to encourage the development of really strong shoots. Note that the shoots you want to encourage are those at the broad end of oval cultivars, and the sunken eyes on round cultivars. Rub off any other sprouts. You can plant them as the shoots develop, ensuring that the sprouts face upwards, out of the soil.
 
If you plant the seed tubers directly in the ground, you will eventually see the sprouts emerging from the soil. Well sprouted tubers should push through after about two weeks. It is at this point that the plant will begin to develop roots that will push down into the soil under the tuber.
 
If you have planted in autumn or fall (bearing in mind that spring and autumn are the best times to plant), if there is a sudden cold spell, throw grass cuttings over the plants to give them some warmth and protection.
 
Stalks and Leaves
Once the first buds have sprouted, the plants will start to form stalks and leaves above the soil. You can be sure that the roots will also be developing underground. The new potatoes will later start to form on these "underground stems" and rhizomes.  
 
As the greenery develops, and the plants grown, you should start to "hill up" the potatoes, by drawing a little loose soil up over the shoots – but without covering them. By the time the flowers appear, you should have created a rather substantial ridge.
 
During this period of growth, you need to water regularly, but try not to wet the foliage too often. A drip or furrow method of irrigation is preferred. You also need to vigilant about weeds, removing them so that they don't compete for nutrients or water. Just don't use any sharp tools, because if you damage the underground tubers, this could lead to infection by fungi, or to disease. If you spot any cracks or gaps in the soil, fill these to reduce the possibility of tuber-moths attacking the potatoes. This will also prevent unwanted "greening" underground.  
 
These two stages will take anything from a month to 70 days, depending on specific conditions.
 
Flowers and Tubers Develop
Even though different potato cultivars vary in terms of their capacity to flower, it is during the flowering stage that the tubers begin to form at the ends of the rhizomes that have developed underground. It is a very stressful stage for the plant, and regular irrigation is vital.  
 
The Tubers Bulk Out
Though you obviously can't see what is happening underground, the fourth stage in the potato's growth is when the tuber gets bigger and accumulates starch.
 
It is at this point that you can harvest "new potatoes", by carefully digging under the tubers, and removing some of the small, newly developed potatoes at the base of the plant.
 
This phase can last as long as three months, however home gardeners often harvest small quantities of potatoes throughout this period of time.
 
The Plant Matures
You will notice that the leaves begin to turn yellow and start to drop off the plants. Gradually reduce the quantity of water, so that the tuber skins can "set" or harden.
 
If the weather is dry you can leave the tubers in the soil for a while. But if it is wet, or there is even a chance of rainy weather, lift them so that they don't absorb the moisture and possibly develop deformities.
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