Growing Potatoes

The flavour of store-bought potatoes simply does not compare to homegrown potatoes - especially the new waxy potatoes at Christmas time! Grow your own and enjoy the bragging rights at the Christmas dinner table.

When it comes to choosing what variety to grow, it can be confusing to know what to choose…

There are early, main and late varieties which have different maturity times and different keeping abilities. If you just want to grow some waxy potatoes for Christmas, choose an early variety such as Jersey Benne, Rocket or Liseta. These varieties tolerate the cool early season and are the quickest to mature. You can get planting in August in warm mild districts, and in early September in cold districts, but will need to protect the tops from late frosts. If you want them for Christmas, you will need to count back to ensure they are planted in plenty of time to produce. They can take 70-90 days. They tend to have lower yields than other varieties and don’t store well for long periods.

If you love fluffy roast potatoes and mashed spuds, a main crop variety might be a better choice for you such as the crowd favourite Agria which takes approximately 100 days. Main crop potatoes are best planted in September - October.

The later varieties are those that tend to be slower to mature but have high yields and they store well. Heather and Rua are both good varieties if you want to grow and store them in winter.

Why do I need to buy ‘seed’ potatoes? Why can’t I use the ones sprouting in my pantry?

Seed potatoes are grown in areas that are confirmed to be free of potato viruses that can severely reduce your harvest and you are guaranteed that the variety you grow is the variety that you bought!

Where do I grow the potatoes?

They will grow best in a warm, sunny spot, sheltered from strong wind. They will fail to thrive or yield if they are in too much shade or are competing for light and moisture. The size of the area depends on the size of your family and if you want to grow enough for storage.

They need a free draining soil that has plenty of compost in it. If you have clay or poor draining soils, you will need to raise up the beds at least 15 cm to get good results.

Once I’ve bought the seed potatoes - now what?

Ideally you will lay your seed spuds out in a tray (an egg carton is perfect) in a cool, light space for a few weeks to encourage them to sprout. This is also called ‘chitting’. They should have strong growing sprouts before you plant them.

A week before planting, dig a trench about 10 cm deep and work in some lime. Before planting, work some potato food into the soil and plant them 40-50cm apart. Space the rows about 80cm apart. Potatoes form on the stem of the plant so in order to get a good harvest, a significant amount of the stem needs to be buried.

This happens by ‘mounding up’. When the potato tops have emerged to about 20cm high, ‘mound up’ the soil until the tops are almost covered. When the tops grow another 20cm, mound up again. This creates a large mound that the potatoes can grow within.

Potatoes can handle some dry weather but if you are not getting some regular rainfall, you should water them regularly.

Keep an eye out for -

At any time of the growing season, if there are cool wet conditions late blight can be a problem. It spreads rapidly, with brown/black splotches on the leaves turning into complete leaf drop. Apply Grosafe Free Flo copper thoroughly, including the underside of the leaves at the first sign of black spots.

Potato psyllid is a relatively new pest in NZ - it looks like a small mosquito/fly. It ruins potato crops by infecting the plants with a bacteria that prevents tuber development leaving you with little or no crops or in the case of late season attacks, leave fully developed tubers with a dark ring in the flesh and a bitter taste.

Psyllid aren’t usually present until temperatures are consistently warm so early crops can escape damage but it is safer to spray regularly with a mix of Grosafe Enspray 99 + BioNeem or securely cover with bug netting or a Net Tunnel allowing room for the tops to grow.

In areas where psyllid is well established or when growing late season crops the only successful treatment is to cover the crop with bug netting or a Net Tunnel. 

Written for Gubba by Kelly Jean Reyland from Garden Advice NZ (www.gardenadvice.co.nz)