Potato Valor
If you're only going to grow one potato, I recommend growing our new/early potato 'Charlotte'. The home grown flavour is outstanding.
If you'd like a potato crop to follow on from Charlotte, then Valor is an excellent choice. Importantly, it has good resistance to 'blight' - a disease which often attacks potatoes maturing later in the year and turns them to a black gooey pulp!
Valor also has very good storage qualities making it ideal for harvesting and keeping through the winter.
Time from seed to plate: 12 weeks
Sowing Calendar
Sow
It's best to encourage seed potatoes to produce new shoots before you put them in the ground. Do this by saving up a few egg cartons and placing a potato in each compartment, standing so that the end with the most 'eyes' is pointing upwards. Put them in a cool, dry and bright place for about 4 weeks, and new shoots will emerge. The process is called 'Chitting'. (If you haven't got time, or can't be bothered, just bung them in your soil un-chitted - they'll still grow very well!)
Plant them in May. Potatoes are very hungry feeders, so make sure you've got lots of compost or manure in the soil. You only want to leave the four biggest shoots on each potato, so rub the others off. Create a hole with your trowel, and place a potato in, ensuring the top's at least 6in deep.
Follow the spacing plan, leaving at least 2ft between each spud. Maincrop potatoes like these produce very big plants, so they need more space than early/new potatoes.
Grow
When the first shoots are about 6in high drag soil up from either side to practically bury them, just leaving a few leaves showing. This is called 'earthing up' and encourages new shoots to form underground that will produce more potatoes.
If the leaves start to turn black or rot this is probably blight. The best thing to do is chop off all the foliage before the blight makes its way down to your potatoes.
Wait a few days until any blight spores on the surface of the soil have died off, then harvest the whole lot.
Dispense with any infected foliage well away from your plot, and grow next years potatoes in a different spot, ideally one which hasn't been affected by blight for 3-4 years.
Harvest
You can start harvesting when the plants begin to flower, normally some time in August/September.
Either dig up individual plants for immediate use, or dig up the whole lot for storing.
If you're going to store them, leave the potatoes on the top of the ground for a day or two to encourage the skins to harden. Then store best in hessian sacks, kept somewhere dark and frost free like a garage or barn.