POTATOES

Selecting the site

Potatoes will grow best in a warm sunny position. They will not grow and yield in shade or where they must compete for light and moisture. Shelter from strong winds is also a benefit.The size of the potato garden depends on the size of your family and your requirements. 

The soil

Potatoes require a free draining soil rich in organic matter (add compost). In clay soils, the potato plot should be raised or built up some 15cm above the surrounding soil to ensure good drainage. 

‘Seed’ potatoes

Potatoes are grown from tubers known as ‘seed potatoes.  These ‘seed potatoes’ are grown especially for the purpose in areas that are free of virus diseases. Potato virus diseases can severely reduce yield if the seed potato is infected.  Avoid cheap seed potatoes which may not be virus free. 

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Potato varieties

With potatoes being a major vegetable in our diet, not surprisingly there are numerous varieties with distinct differences in shape, colour, size, yield, time to maturity, taste, and suitability for mashing, boiling, baking, or chipping.  

When choosing varieties, it is a good idea to select ones that meet your needs and give a spread of maturity with the late ones being stored for the winter. 

Early varieties are those that tolerate the cool early season and are quickest to mature. They tend to be lower yielding and not good keepers, but they are great for that early taste of new potatoes. They can be planted in winter in warm mild districts, and in early September in cold districts, but will need protection from late frosts. Popular early varieties are – Rocket, Swift, Cliffs Kidney, Ilam Hardy and Jersey Bennes. 

Main crop varieties have an intermediate growing period, maturing in 100—120 days. These varieties are best planted in September and October. Good main crop varieties include - Red Rascal, Desiree, (red skinned varieties) which are good all-purpose potatoes; Agria, a popular baking and mashing potato with pale golden flesh and great taste. 

Late varieties tend to be the slower to maturity, high yielding and good for storage. Good late crop varieties are – Heather, a purple skinned variety (the purple disappears with cooking) which has firm large tubers and a high yield. It is a general-purpose variety which keeps well; Rua, an older type which produces high yields of large oval flat tubers is a good keeper.

Sprouting

It is a good idea to ensure ‘seed potatoes’ have a good strong growing shoot emerging from the tuber prior to planting. Buy your ‘seed potatoes’ a few weeks in advance of planting time and place them in a tray positioned in a warm light position. This process, called ‘chitting’ will encourage sprouting. An egg carton makes a useful tray. 

Planting

Potatoes are tubers which form off the underground stem of the plant (They are stem tubers not root tubers). Hence to produce a good crop it is necessary to ensure there is a significant amount of stem covered with soil. Plant ‘seed potatoes’ in a hole about 100mm deep, about 400—500mm apart in rows about 800mm apart.  

Mounding up

When the shoots have emerged to 200mm high, mound up the soil almost covering the emerged tops. When they have grown another 200—300mm, repeat the process. This produces a large, mounded row in which the new potato tubers will form and grow. 

Watering

Potatoes tolerate reasonably dry conditions, but in very dry weather they may require regular watering.

Feeding

Prior to planting, apply a dressing of lime. Work this into the soil and leave for a week, then add Superphosphate or ican Potato Food and work this into the soil.  

Pests and diseases

The major disease of potatoes is late blight. Despite its name, it often occurs early in the season. The fungus usually attacks in wet cool conditions. Once infested it will spread rapidly. Initially brown to black blotches appear on the leaves, which spread to total defoliation. Control by spraying at the very first sign of black spots with Grosafe FreeFlo Copper every 2 to 3 weeks. Spray thoroughly including the undersides of leaves.

Tomato Potato Psyllid, a recent pest to NZ, is avoided by planting early in the season and by spraying regularly from very first sign with Yates Mavrik.  

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