Potatoes

Why Grow It?

Where would the GIYer be without the humble spud? Spuds can be grown pretty much anywhere and will actually improve poor soil.  They produce a high yield from a relatively small space and store well.  No wonder they have been a staple diet for Irish families for centuries.  Digging for your first new potatoes will be like Christmas morning – promise!  

Sowing

Effectively there are two types of potatoes – earlies and maincrop.  Earlies grow quickly, have no skin worth speaking of, and are usually out of the soil before blight arrives.  Maincrop develop later, produce a higher yield, develop a thick skin and can therefore be stored – they are, unfortunately, more vulnerable to blight as they are in the ground during the summer months when blight conditions prevail.

Potatoes are grown from “seed potatoes” which are potatoes saved from the previous year’s crop.  It was traditional for Irish GIYers to save their own seed potatoes but this is generally out of favour now – better to buy certified seed potatoes each year, in case your own potatoes carry over a virus. 

“Chitting” the seed potatoes is allowing them to sprout to give them a headstart before sowing.  Start this process in February – lay the seed potatoes out in a shallow tray or used egg cartons and leave them somewhere relatively bright and cool.  By March they will have developed green sprouts.  Some people pick off all but three of the sprouts before planting.

The soil in which you are planting potatoes requires a generous application of well-rotted farmyard manure, compost or seaweed before planting (ideally the previous winter).  Too much nitrogen however encourages leafy growth at the expense of the tubers. Sow first earlies in mid March (St Patrick’s Day traditionally) in single rows, 15cm deep, 25cm apart and 45cm between rows.  Maincrop spuds are sown in mid to late April.  Increase spacing to 35cm.  It is vitally important to include potatoes in your crop rotation as they are susceptible to disease if grown in the same ground year on year.

Growing

Cover young plants if there is any risk of frost. Potatoes require “earthing up” – this is a process of covering the stem (also called a “haulm”) with soil.  Since the potatoes grow along the haulm, the more of it that is buried beneath the soil, the more spuds you get.  Use a draw hoe to bring loose soil from around the plant up against the stem.  When the stems are 20cm high draw soil up leaving just 10cm of foliage above the surface.  Repeat once or twice during the summer, particularly if you see spuds popping through the soil – spuds go green if exposed to the light and are inedible (and poisonous).

Harvesting

Check earlies in mid June to see how they are getting on.  Earlies will be ready about 14 weeks after sowing.  Maincrops take 18 weeks.  The presence of flowers on the plant is often (but not always) an indicator that the spuds are ready.  We typically leave our earlies in the ground and dig as required - their thin skins mean they don’t store well.  They do fine in the ground until September at which point we move on to maincrop.  Maincrop can stay in the ground until the first frosts – but they are susceptible to scab, worms and slug damage so probably best to lift and store in sacks in October/November.  Be sure to remove all spuds from the ground, even the tiny ones, when harvesting – if left in the soil they will sprout next year, causing problems for the crops that are planted there.

Recommended Varieties

  • Orla (earlies)
  • Homeguard (earlies)
  • Duke of York (earlies)
  • Cara (maincrop) 
  • Pink Fir Apple (maincrop) 
  • Sarpo Mira (maincrop blight resistant)
  • Setanta (maincrop)

Problems

Frost damage is a real problem for early sowings.   Common scab on the skin of potatoes looks poor but doesn’t affect the spud.  Slugs are a real problem, eating holes in to the spuds. 

The fungal disease potato blight is the bane of the potato grower – the first symptoms are dark decaying spots on leaves.   Heavy rainfall and warm, humid conditions are ideal blight environments.  Use blight resistant varieties such as sarpo mira, orla, setanta and cara.  

GIY Tips

  1. If blight strikes, cut down the stems immediately, leaving the tubers in the ground, they won't grow any more, but the blight won't reach them.
  2. When storing maincrop potatoes, cut the stems down and leave the spuds in the ground for 10 days to allow the skin to mature. Store potatoes in hessian sacks in a dark, cool shed, do not store any damaged ones.