How to grow potatoes

There is nothing quite like the taste of new potatoes straight from the garden. Add to this the satisfaction and sense of achievement, the savings, the knowledge that your potatoes are free of nasty pesticides and you have some very powerful reasons for growing your own. This article will assist you to produce a supply of new potatoes well before Christmas, plus a summer / autumn maturing crop which will last through winter and early spring.

Potatoes grow best in a warm sunny position, and they're easy to grow with good yields leading up to Christmas and through summer.

Key Points for Success

• Warm, sunny site
• Fertile, well drained soil - dig in plenty of compost when preparing soil
• Quality seed potatoes
• Water during dry periods
• Planned succession of varieties

Cultural Requirements

• Add Tui Potato Food - 150gm/m²
• Seed potatoes should be sprouted before planting - about 4 weeks prior to planting
• Plant when sprouts are 1-2cm long
• Remove all but 3 or 4 strong shoots
• Plant in rows 5-cm deep (N.B. Rua should be planted shallow - 2cm deep) with sprouts pointing upwards
• Space rows 60cm, potatoes 30 cm apart along each run
• As plants grow, mound up soil around them this helps to keep sun off tubers and stops them turning green
• Keep soil moist especially at planting time
• Avoid watering foliage if possible, to stop spread of disease

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
• 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
• 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

Potato Varieties

When choosing varieties it is a good idea 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 are those that tolerate the cool early season and are quickest to maturity. 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.

Ilam Hardy

• Tubers oval to round, white skin and flesh
• Good yield over wide variety conditions
• Excellent for both boiling and frying
• Early or main crop

Cliffs Kidney

• Tubers kidney shaped, slightly pink skin, white flesh

Maris Anchor

• Oval shape, white skin and flesh
• Excellent cooking qualities
• Excellent keeper
• Suitable for main crop

Rocket

• New early variety
• Round shaped tubers, white skin and flesh
• Fastest producing of early varieties, ready in 60 -90 days

Nadine

• Round, white skin and flesh
• Waxy boiling potato

Main crop varieties cover most, which have an intermediate growing period, maturing in 100 - 120 days. These varieties are best planted in September - October. 

Good main crop varieties include: Red Rascal, Desiree, (red skinned varieties) which are good all purpose varieties. Agria, a pale golden flesh with great taste and good for mashing.

Desiree

• Oval shape, red skin, yellow flesh
• Needs fertile soils
• Good all round cooker, excellent for chips

Rua

• Oval to round, white skin and flesh
• Excellent cooker - boil and bake
• Heavy bearer in most soils

Karaka

• New variety - great all rounder
• Excellent yield and taste
• Grows well in all conditions

Agria

• Oval, white skin, yellow flesh
• Good for chips and baking

Red Rascal

• Oval, red skin, white flesh
• Good all purpose potato

Late varieties tend to be the slower to maturity, high yielding, and good for storage varieties. Good late crop varieties are:

Heather

• A purple skinned variety (the purple disappears with cooking) which has firm large tubers and a high yield. A general purpose variety which keeps well

Rua

• An older type which produces high yields of large oval flat tubers. A good keeper

Van Rosa

• A newer variety with great taste

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 will encourage sprouting.

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
• 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 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 Tui General Fertiliser or Potato Food and work this into the soil.

Harvesting / Storing

• Harvest early varieties when flowers fully open (3 months after planting)
• Main crop and late varieties ready when foliage dies off
• Dry thoroughly, place in shallow boxes in cool, dark position
• Cover with dry sacks or sphagnum moss etc to keep out light

Pests and Diseases

• Late Blight. The major disease of potatoes and despite its name, it often occurs early in the season or late. Pale brownish lesions on leaves and stems, leading to collapse of foliage. It usually attacks in wet cool conditions. Once infested it will spread rapidly. Initially black or brown blotches appear on the leaves, which spread to total defoliation. Control by spraying at the very first sign of black spots with Yates Fungus Fighter or FreeFlow Copper. Spray thoroughly including the undersides of leaves
• Aphids
• Potato Tuber Moth
  • Caterpillars bore into tubers making them worthless
  • May also mine / feed on leaves or exposed tubers
• Potato Psylid - see below

A major newly arrived pest of potatoes is the Potato psylid. 

• The limpet like insect attaches itself to the undersides of leaves
• As it sucks the sap it also injects a toxin into the plant which inhibits the formation and sizing of the new potato tubers
• Once this pest is present in your area, regular preventative spraying with Yates Mavrik is required from December - April
• Early planted crops harvested before mid January are much less likely to be attacked

Pest and Disease Control

• Blight
  • Fungus Fighter 
  • FreeFlow Copper 
• Aphids, Tuber Moth
  • Maveric