Seed Potatoes in Ireland

The tradition is St Patrick's Day, and in a mild coastal garden in Cork, Kerry or Wexford that works for first earlies. For most of the country it is optimistic. What matters is soil temperature and drainage, not the date, so wait until the soil is workable and not sodden. In practice that means mid to late March for first earlies in the south and along the coast, April for first and second earlies almost everywhere else, and late April into early May for maincrop. A crop planted into cold wet soil in March sits and sulks while an April planting catches it up by June.

For first earlies, yes, it is worth it, because sprouting the tubers before planting gains you roughly two to three weeks and that can be the difference between lifting in late June and lifting in mid July. Stand the tubers in egg boxes or a shallow tray with the blunt end that carries most of the eyes facing up, somewhere cool, bright and frost free such as a spare bedroom window or a porch, from late January or early February. You want short, stubby, dark green or purple sprouts about 2cm long, not long white shoots, which mean the room is too warm or too dark. For maincrop it makes far less difference and plenty of Irish growers skip it entirely.

Do not. Ware potatoes are usually treated with a sprout suppressant, so many will simply never grow, and those that do can bring blackleg, virus or potato cyst nematode into ground that then stays infected for years. Certified seed potatoes are grown in inspected crops in areas chosen for low aphid pressure and sold with a certification label. They cost a few euro for a net that will fill a bed, which is cheap insurance. The same applies to saving your own seed year after year: virus builds up invisibly and yields drift downwards, so buy fresh certified seed each season.

The Sarpo varieties, particularly Sarpo Mira and Sarpo Axona, are in a class of their own and will often still be standing green in September when everything around them has gone. They are very floury and not to everyone's taste. Among varieties Irish gardeners actually eat by choice, Setanta and Orla were both bred in Ireland with blight in mind, and Cara has long had a reputation for holding on late. No variety is immune, and resistance to the leaf blight does not always mean the tubers are safe too, so cut the haulm at the first sign regardless of what you planted.

A 2kg net usually holds somewhere between fifteen and twenty five tubers depending on their size, which at 30cm apart plants roughly five to seven metres of row. As a working figure, expect about 1kg of potatoes per plant from first earlies and up to twice that from a well grown maincrop in a decent year. Earlies are the better use of a small garden, because they occupy the ground for only three months, come out before blight arrives, and taste like nothing you can buy.

Yes, and it suits Irish gardens with heavy soil or no space. Use a bag or barrel of at least 40 litres, put three tubers in a 40 litre bag or one in a large bucket, start with 15cm of compost and top up as the shoots grow until the container is nearly full. First earlies are the best choice because the crop is over before the compost exhausts itself. The one thing container potatoes will not forgive is drying out, and a bag in a sheltered spot can need watering daily in July even in an Irish summer.

Three things. It stops light reaching the developing tubers, which would turn them green and inedible. It protects emerging shoots from late frost. And it puts several centimetres of soil between blight spores washing off the leaves and the tubers below, which is the part most people do not realise. Draw soil up from between the rows with a hoe or spade when the shoots are about 20cm tall, leaving the top few leaves showing, and repeat once or twice more until the ridge is 15 to 20cm high.

Those are potato fruit, and they are poisonous. Potatoes are in the same family as tomatoes, so some varieties set small green berries after flowering in a good summer. They look exactly like unripe cherry tomatoes, which is precisely the problem in a garden with children in it, and they contain enough solanine to make someone quite ill. Pick them off and bin them rather than composting them where they might be found again. They are not a sign of anything wrong with the plant and removing them does not affect the crop underneath.