Potato growing guide
Guide to Growing Seed Potatoes
Early varieties are ready for harvest three months after
planting.
Potatoes are native to the Peruvian Andes and were brought to
Europe by Spanish explorers in the 16th century. Cultivation
quickly spread. Potatoes are now part of the staple diet of the
western world. High in fibre, vitamin C and B, as well as having
more protein and iron than most vegetables, potatoes are a meal in
themselves.
When and where to plant
Potatoes are planted after frosts have passed in early spring
through to early summer. In warmer regions of New Zealand potatoes
can be grown year round.
Potatoes require a sunny situation and rich well-drained soil with
plenty of organic material, such as compost, dug in. Before
planting, dig in a specially blended potato fertiliser at a rate of
100g per square metre. Early maturing varieties require a sheltered
sunny position to get a head start. Main crop potatoes require a
lot of space in the garden, so if space is limited, grow an early
maturing variety.
Planting
Potatoes are grown from tubers known as seed potatoes. As potatoes
are prone to virus, it is very important that only "certified virus
free" potatoes are planted to ensure a successful crop.
Potatoes are classified into two groups depending on planting time
- early (also known as "new" potatoes) and main crop. Some
varieties are suitable for both.
Seed potatoes need to be pre-sprouted before planting. Lay them out
in a single layer onto a seed tray and place in a warm sunny
sheltered spot. The potatoes will turn green and sprouts appear
from the "eyes", which are small buds. The "eyes" grow into shoots.
When the shoots are 3-4cm long they are ready to plant out. Remove
all but three of the strongest shoots for planting. Sprouting
usually takes 4-6 weeks.
How to plant
Potatoes are planted in furrows approximately 10cm deep. Early
maturing varieties are spaced 25cm apart and main crop varieties
35cm apart. Space the rows 80-100cm apart. Cover the seed potatoes
with soil taking care not to damage the shoots.
As soon as shoots appear through the ground, mound soil around them
to protect the new growth. Mounding prevents developing potatoes
from "greening" and prevents attack from the Potato Tuber Moth.
Mounding is essential to produce abundant crops as potatoes form on
the stems. Continue mounding until the potatoes start to flower and
growth slows down.
Mounds should be kept weed free.
Feeding and watering
Potatoes are gross feeders and require regular feeding
throughout the growing season. Use a specially blended potato
fertiliser at the recommended rate. Keep the soil moist, especially
at flowering time. Keeping and cooking qualities are affected if
growth becomes checked due to erratic periods of dry and wet
weather. Water between the mounds rather than on the foliage as
potatoes are susceptible to blight which is spread by water
splash.
Harvesting and storage
Early varieties are ready for harvest three months after planting,
when the flowers are fully open. Main crop varieties should not be
dug until the foliage has completely died down, usually in late
March. Take care when harvesting potatoes not to damage the tubers
as keeping quality can be affected. Do not leave potatoes exposed
to light once they have been dug. If they are to be stored,
potatoes must be dry and stored in sacks placed in a cool, dark,
well-ventilated place.
Pests and diseases
The biggest problem affecting potatoes is Late Blight which usually
occurs early in the season when conditions are warm and humid with
cool nights, or late in the season with the autumn rain. Leaves and
stems develop greenish brown/black patches, until eventually the
whole plant turns black. Use a preventative spray such as Champion
Copper or Bravo at regular intervals.
Aphids are small green insects that cause leaves to distort and the
plant to wilt. Spray with Mavrik. The Potato Tuber Moth larvae
cause holes in the leaves and tunnels in the stems and tubers.
Spray with Orthene. When spraying, make sure the under side of the
leaf is sprayed as well as the topside.
Rotate crops so that potatoes are not grown in the same place each
season.
