Grow Potatoes for a Christmas Crop

13 August 2015, written by Benedict Vanheems

For many vegetable gardeners the humble potato is the epitome of everything that’s good about growing your own: they’re fun to grow, exceptionally versatile in the kitchen and they’re pretty darn tasty!

Fortunately, the potato season isn’t over when the last of the summer spuds are harvested. Plant some seed potatoes in late summer and you could be enjoying a bonanza of earthy nuggets from late autumn right through to Christmas. Just imagine serving up your own tender new potatoes with the festive meal – what a treat!

Second Crop Potatoes

Potatoes planted in summer are called second-crop potatoes. Seed potatoes (potato eyes in the US) for second cropping are sold by garden suppliers and potato merchants anytime from mid to late summer. The seeds are exactly the same as those sold for spring planting, only these ones have been held back in a cold store to stop them developing any further; they’re literally in suspended animation.

You can save your own seed potatoes for second cropping by keeping some of your spring seeds back. Keep them on a cool, bright windowsill. Check the shoots periodically for aphids and plant them before they begin to wither.

If you’re thinking you could simply replant some of your summer-harvested potatoes, I’m afraid this will only meet with disappointment. Potatoes need a period of dormancy before they can sprout into a new plant, so in this case you really will need to start with genuine seed potatoes.

Planting Second Crop Potatoes

Second-crop potatoes take about three months to reach maturity. They are grown in exactly the same way as spring-planted potatoes with two important exceptions. First, the warmth of late summer means that second-crop seed potatoes do not need to be pre-sprouted – they’re primed to get growing without delay. Second, you’ll need to consider the risk of frosts later on in the growing cycle and take the necessary precautions to avoid damage to your plants.

The easiest way to grow second-crop spuds is in containers. A small pot just 30cm (one foot) tall and wide can hold one potato plant, while larger containers up to the size of a dustbin could hold up to four. Set the seeds onto a layer of compost or potting soil about 10cm (4in) deep, or deeper if your container is particularly tall. Cover over with another 10cm (4in) of compost then add more compost as the stems grow, topping up 5-10cm (2-4in) at a time until the top of the container is reached.

Keep containers well watered because the compost can dry out quickly, even in wet weather. Apply an occasional feed of liquid fertiliser (home-made fertilisers are great for this purpose).

If you want to grow potatoes in the ground first consider how much of the growing season is left. You need to allow enough time before the temperature drops and growth slows right down.

If time allows you to grow your spuds in the ground, pick a warm, sunny spot to ensure the quickest growth and the best chances of success. Position the seed potatoes 30cm (12in) apart along the bottom of trenches spaced at least 60cm (24in) apart. Cover them over then once the stems reach about 20cm (8in) tall, begin earthing up by drawing the soil up around the stems to create ridges. This creates more ‘room’ for the developing spuds to grow into (container potatoes are topped up as they grow for the same reason).

Protecting Potatoes from the Cold

Containers have the obvious advantage of being portable, so when cold weather threatens it’s easy enough to move plants completely under the cover of a greenhouse, polythene tunnel or conservatory. You can also protect plants against light frosts by wrapping the container in layers of corrugated cardboard or bubble wrap.

Potato foliage can be kept snug with an insulating layer of fleece, removed during the day to allow maximum sunlight penetration.

Harvesting and Storing Second Crop Potatoes

The moment of truth is when the leaves start to turn yellow and die back. At this stage cut the foliage off and put it on the compost heap. Now prepare to unearth your spuds – a joyous moment indeed!

Container-grown spuds can be upturned and the compost torn apart to reveal the tubers. If you’ve grown them in the ground, use a border fork to carefully dig the plants up, starting some way from the plant to avoid accidentally spearing your hard-won tubers.

Potatoes can be enjoyed immediately, but if you want to have a shot at keeping them until Christmas leave the spuds untouched in containers, keeping the compost barely moist then unearth them when you are ready. You should have no problems holding them back for an extra month or two provided conditions remain cool but frost-free.

Whether or not you choose to leave potatoes in the ground depends on how cold early winter is in your part of the world. In temperate regions, little more than an extra pile of earth strewn over the top of the rows should be enough to provide an additional layer of defence against occasional frosts. If winters are severe or your soil is wet and heavy, then you’re safer lifting all of the potatoes to pack them into boxes of coarse sand kept in a frost-free place.

If you thought growing potatoes was hugely satisfying, second-crop potatoes will prove even more so! Give your holiday season dinners a home-grown boost and try them for yourself.