The delight of homegrown, tender new potatoes on Christmas Day is closer than you may think and possible with a little know how.

It’s useful to know what makes a winter seed potato. The simple answer is that they have been in cold storage all spring to delay their growth and taken out from June so that they are ready to start their 12 to 14 week plant-to-harvest cycle. These timings are given for spring planting and it must be remembered that there is not as much heat or light in the autumn and so plants will take longer and the yields may be less. A potato planted in July or August can produce your ‘roasties’ and new baby potatoes for Christmas Day! Depending on where you are, we would say mid-August would be the latest you could plant, however, we envisage most customers will plant by the end of July. Your feedback on growing late potatoes is most welcome as we are on a learning curve with our customers.

It’s also useful to know that potatoes harvested in summer require a period of dormancy before they can be used as seed potatoes, so replanting these straight away won’t work.  Potatoes planted in late summer would benefit from chitting for around 3-4 weeks, however, this isn’t necessary.

How to grow potatoes indoors for Christmas harvests

1. Use a container at least 30cm (1ft) deep and wide, with drainage holes in the base.
2. Add a layer of potting compost or garden soil mixed with garden compost or well-rotted manure. A layer 10cm (4in) thick is sufficient for 30cm (1ft) deep pots, but larger containers can be half-filled.
3. Plant one to three tubers per pot, each with about 30cm (1ft) of space, and cover with 15cm (6in) of compost or soil.
4. As the foliage develops, earth up the potatoes with further compost or soil until the container is full to within 5cm (2in) of the top. Leave a lip to aid watering.
5. Keep well-watered and feed with a general-purpose liquid fertiliser.
6. Ensure the greenhouse remains frost-free as the season progresses, as potato foliage would be damaged by frost.
7. The foliage will yellow and die down in late autumn and can then be removed and composted.
8. Tubers can be left in their pots in compost (kept fairly dry) until needed at Christmas.

How to grow potatoes outdoors for Christmas harvests

1. Follow general instructions for growing potatoes, including planting them in a trench and earthing them up as they begin to grow.
2. Take measures to protect against potato blight and slugs.
3. Once foliage dies down in September or October, remove and compost it.
4. On light soils in a sheltered garden, piling some earth up over the row where you know the potatoes are and covering it with straw to insulate tubers may be sufficient protection to store them in the ground until Christmas.
5. In cold areas, or where soils are wet and heavy, it is better to lift tubers by the end of October and re-bury them in coarse sand or soil in a frost-free place (such as a garden shed) until you need them.
6. Lifting and storing potatoes in the fridge, or in bags in a cool shed, is possible but will cause the skins to harden and the desirable, delicate ‘new-potato’ flavour and texture will be lost.

Problems

Most of us will have tremendous results but watch out for a few 'troubles' along the way- solutions to troubles can easier to remedy than you think. There is much less light and heat in the autumn months and so everything will take longer than in the spring and summer.

• Potatoes are prone to scab and a number of rots but this can usually be avoided when they are grown in fresh compost in containers. 
• Slugs and snails can damage foliage, stems and tubers underground. Look out for slugs when the weather is cool or moist, try using a 'wool pellet' slug deterrent.
• Potatoes grown outside in summer and autumn are especially prone to potato blight. Those in containers indoors are not usually at risk. Ensure your pots of potatoes are 'spaced' out and bunched together, and avoid planting tubers too close together when in the ground.
• Keep an eye on the weather forecasts as early frosts will blacken foliage and weaken plants; fleece protection may be needed for outdoor crops.