Growing great spuds

Selecting the site.

Potatoes will grow best in a warm sunny position. They will not grow and yield in shade or where they have to 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 (compost). In clay soils, the potato plot should be raised or built up some 15cm above the surrounding soil to ensure good drainage.

The ‘seed’ potatoes

Potatoes are grown from tubers known as ‘seed potatoes’. Seed potatoes are grown especially for the purpose in areas that are free of viruses. Potato virus diseases can severely reduce yield if the seed potato is infected.  

Avoid cheap seed potatoes which may not be virus free.

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

Potato varieties

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

Early varieties

These varieties tolerate the cool early season and are the 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 August 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  

These are the majority of varieties which have an intermediate growing period, maturing in 100—120 days. These varieties are best planted in Sept—October. 

Good main crop varieties include -Red Rascal  and Desiree, which are good all-purpose red skinned varieties. Agria is a favourite which makes superb fluffy roast or mashed potato.

Late varieties

These tend to be varieties that are slower to mature, 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 with a high yield. A firm waxy general-purpose variety which keeps well and Rua—an older type which produces high yields of large oval flat tubers. A good keeper.

Sprouting (Chitting) 

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 will encourage sprouting.

Planting

Potatoes are tubers which form off the underground stem of the plant. (They are stem tubers, not root tubers). Therefore, to produce a good crop it is necessary to ensure there is a significant amount of stem covered with soil.

The seed potatoes are planted in a hole about 100mm deep, about 400—500mm apart in rows about 800mm apart. 

Mounding Up 

When the potatoes 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 moderately 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 a general NPK Fertiliser or Potato Food and work this into the soil.   

Pests and Diseases of Potatoes

The major disease of potatoes is late blight. Despite its name, it often occurs early in the season or late. It 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 (leaf drop). 

Control by spraying at the very first sign of black spots with  Grosafe Free Flo Copper  (The most effective, lowest copper footprint and lowest cost of all the copper sprays)

Spray thoroughly including the undersides of leaves.

Potato psyllid, a new pest in NZ, devastates potato crops by injecting a bacterium into plants preventing tuber development or in the case of late season attacks, leave fully developed tubers with a dark ring in the flesh and a bitter taste. Damage can be minimised by planting early in the season and by spraying regularly from very first sign with Yates Mavrik, Yates Success Ultra or for organic growers a mix of Grosafe Enspray 99 +  BioNeem. In localities where this pest is well established or for late season crops the only successful treatment is to cover the crop with fine bug netting.  

For more information on growing potatoes refer to our Pro Advice Guide.