Documents: Latest From: Carla Allen:

Problems With Potatoes
by Carla Allen
by Carla Allen

Greetings from Nova Scotia!

Carla Allen has been gardening for the past 25 years, co-owned a nursery in southwestern Nova Scotia for 16 years.

Carla has an extensive image library and nurtures a network of horticulture in the region. She was the first president of the Yarmouth Garden Club.

September 30, 2007

The majority of garden crops are safely harvested now. For some people the experience was a time of discovery. Take potatoes for instance. All summer their progress was mostly hidden from view. When it came time to dig them up, the appearance of some was not quite what was expected.

Sheila Goodwin planted potatoes this year with a friend and both were surprised at what they unearthed at harvest time. Many of their potatoes looked like each had joined with several smaller ones. She wanted to know what causes this.

Tawnya MacNeil, Resource Information Officer for AgraPoint International Inc. in Truro, says that the the underlying cause for the “knobbiness” is genetics, but it is brought out by environmental conditions, namely moisture fluctuations.

“Potatoes are shallow rooted and need frequent, light irrigation, at least once a week during the growing season. Constant soil moisture is necessary. If the soil dries after the tuber has formed, the potato is genetically programmed to start a second growth after the soils gets moist,” said MacNeil.

Rough, knobby potatoes, and multiples, are the result of multiple growth spurts. Alternate wet and dry conditions can also cause very large potatoes with hollow heart, or cavities near the centre of the potato. Too much moisture will cause rot. Potatoes will not grow well in heavy clay soils; sandy or loam soils are best (the reason PEI has perfect potato land).

Excess nitrogen can also cause knobby potatoes, as well as promote excessive vine growth and decreased tuber growth.

Another problem with potatoes is the development of green skin. This occurs when tubers are exposed to light. Green areas are bitter and inedible. They should be cut away and discarded. The unaffected portion can be eaten. To reduce green skin from forming, hill the soil around the potato plants so developing tubers are not exposed to > light.

Another common problem is potato scab, which appears as ragged, edged, scabs on the tubers.The chance of scab developing increases when you add large amounts of manure or other type of organic matter to the soil. This disease can also be a problem in alkaline or “sweet” soils.

If your potatoes were smaller than you had hoped for, a calcium deficiency could be the reason. Adding calcium to soils can increase the size and quality of your tubers. It can also decrease the susceptibility of tubers to bacterial soft rot which causes internal brown spots.

‘Black heart’ in potatoes refers to dark gray, purple or black areas. This disease is caused by insufficient oxygen in the center of the tubers and can happen if the soil is waterlogged or temperatures are too high.

Store potatoes in a cool, dry, dark, well-ventilated place. They should keep for at least two months. A temperature of around 40*F is best. Don’t let your potatoes freeze. If that happens, they become watery and unusable.


  • New Eden
  • Kids Garden
  • Plant a Row Grow a Row