While most gardeners grow potatoes in open ground, an alternative, (especially for those with limited or no open ground), is to grow first early potatoes in a barrel or similar container.
First early seed potatoes can be planted in barrels from late March (in the south UK) but they will need protection from hard frosts. Planting early should enable the crop to be harvested and a second crop planted in mid summer to provide some more new potatoes in the autumn.
Barrels designed specifically for growing potatoes are available, these often have access holes in the sides, near the base, which can be opened to extract the potatoes when the crop is ready. Alternatively, any sort of barrel can be used although make sure that you know what was originally stored in the barrel, avoid barrels which had chemicals etc. unless you are very certain that any residue will be harmless. Ideally the barrel should be about 1.2m (4 ft) high although smaller containers (such as plastic dustbins) will suffice but the yield will be limited.
Make sure that the barrel is clean and free of contamination, this is especially important the first time the barrel is used - make sure that all residues of any previous contents are removed.
Make sure that the barrel is free draining, add some holes in the bottom if necessary.
Once you have the barrel, decide how many medium sized first early seed potatoes you are going to be able to fit in the barrel, this will depend upon the size of the barrel - a 15cm (6 inch) space needs to be left between each seed potato and the sides of the barrel - sometimes placing one seed potato in the centre and spacing others between it and the sides of the barrel will maximise the number you can fit. Once you know how many seed potatoes you need, select them and chit them (see this page for details of chitting seed potatoes). If you plan to plant a second crop for harvest in the autumn, select additional seed potatoes and store in a dark, cool place.
When your seed potatoes are ready for planting (probably 4 to 6 weeks), turn you attention to preparing the barrel. Remember that the barrel will become heavier as the potatoes grow and you add compost, so try to choose a position where it can be left until the crop is finished - ideally choose a sunny but sheltered position.
With the barrel in place, cover the bottom of the barrel with about 5 to 7.5cm (2 to 3 inches) depth of stones etc. to aid drainage.
Cover the stones with about 12.5cm (5 inches) of well rotted compost mixed with a good general fertiliser.
Then add a layer of general purpose compost to a depth of about 15cm (6 inches).
Plant the seed potatoes, with the main shoots uppermost, into the top of the compost - remember to leave a 15cm (6 inch) space between each seed potato. Cover the seed potatoes with a further 7.5cm (3 inch) layer of compost.
Keep the barrel well watered (but not waterlogged), especially in sunny weather. Include in each watering some proprietary tomato feed or similar.
As the potatoes grow within the barrel, add further 7.5cm (3 inch) layers of compost each time the stems are about 15cm (6 inches) above the top of the compost.
Continue to add compost as necessary until the compost reaches about 5cm (2 inches) from the top of the barrel. Add some stakes into the top of the compost to keep the plants from drooping over the side.
The potatoes will be ready to harvest when the potato plants have flowered - typically late June/early July. If a special 'potato barrel' has been used, access to the potatoes at the base should be fairly easy, just open up an access hole and collect the potatoes you need. Otherwise, if space allows, tipping the barrel onto its side should make the harvest easy but care must be taken as the full barrel will be rather heavy.
The compost will have been exhausted by the growing potatoes, so don't reuse it but add it to the compost heap or dig it in as a soil conditioner.