How to grow

We go to great lengths at Marshalls to make sure our seed potatoes are of the finest quality, giving you the best possible chance of a great harvest. We'd go as far as to say the hardest part about growing potatoes is deciding which varieties to try! After that, the process of planting, caring for and harvesting is relatively straight-forward... but if you do need a helping hand, carry on reading!

Our high quality seed potatoes have been specially selected by our experts for their flavour and reliability. They're all grown in the UK and hold DEFRA or SEERAD certification. Our certified growers undergo regular checks to make sure they have the right processes in place and that the seeds they produce are of a high standard.

Read more about our guarantee to you, as well as some of our best expert tips on how to plant, feed, store as well as protect your potatoes from common pests and diseases, in our handy guide.

What are potato tubers?

Potatoes are grown from small seed potatoes, often called tubers. These are small potatoes that often have ‘eyes’ – the place from which their stems grow under the soil. Always buy tubers that have been certified as being free from disease.

There are four main types of seed potatoes:

  • Salad potatoes are firm, with waxy flesh and a unique flavour.
  • First early potatoes are the first to be ready in the year and are often known as new potatoes.
  • Second earlies follow first earlies and are usually ready for harvest from early June.
  • Main crop can be lifted from September to October or November and stored for up to three months in cool sacks.

When to plant potatoes

  • Salad potatoes can be planted in March or April.
  • Plant first earlies around late March or in April. In warmer areas they can go in as early as February.
  • Second earlies can go into the soil in April.
  • Main crops should be planted any time from mid-April to May.

How to chit potatoes

‘Chitting’ seed potatoes before you plant will help get them off to a flying start. Simply place the tubers in a cool, light place to encourage them to produce shoots.

This process is recommended for first earlies, along with second earlies and salad varieties, but not so much for main crop potatoes.

  • Place the seed potatoes in a seed tray, so that they are just touching, or in sections of egg boxes.
  • Keep the ‘rose end’, where most of the eyes are, at the top – this is where the chits will form.
  • Place the trays or boxes in a cool, light and frost-free environment at around 7°C.
  • The aim of chitting is to form plump, dark green or purple shoots about 2.5cm (1inch) long
  • Thin and long white shoots are a sign of too much heat and not enough light.
  • If shoots are slow to appear, move them to a warmer place about three weeks before they’re due to be planted and leave them there for a couple of weeks, before returning them to a cool spot for the final week.

Watch Our Helpful Video On How To Chit Potatoes

How to prepare the soil for potatoes

Potatoes grow in most soil types but do especially well in a well-drained loam that’s not too heavy.

Ideally, prepare the ground during late autumn or early winter so that the frosts can break down the soil and dig in plenty of well-rotted organic matter, such as compost or manure, to create a reasonable depth. Avoid planting potatoes on ground that’s previously been used for this crop within the past three or four years to avoid the build-ups of pests, such as wire worm, and diseases.

How to plant potatoes

Dig a v-shaped trench, or use a trowel to make individual deep holes, and place the potatoes inside. Rows running north to south will allow the sun’s rays to warm both sides of the crop.

  • First and second early and salad potatoes should be planted 30cm (1ft) apart to a depth of 10cm (4 inches). Rows should be 45cm (1.5ft) apart.
  • Main crop seed potatoes should be spaced 40cm (16inches) apart and 10cm (4 inches) below the soil. Aim to have rows 60cm (2ft) away from each other.
  • When shoots first appear through the soil, ‘earth up’ the potatoes by pulling soil over the shoots from either side to create a ridge. This will protect the plants from late frosts, stop the light from turning potatoes green and encourage more tubers to form further up the stems.
  • The earthing up process can be repeated until the ridge is about 20cm (8inches) high. Feed plants with a specialist potato fertiliser each time if desired.
  • Potatoes are thirsty plants need plenty of moisture while they are growing, especially around flowering time. Water them well during dry periods.

Some growers plant seed potatoes under black polythene, with slits cut for the emerging shoots, and don’t earth up.

Top Tip - Earthing Up

Once shoots have grown to about 20cm high, create a ridge around them by drawing up the soil, leaving the top few centimetres showing. Earthing up encourages more production, and keeps light from the developing tubers, stopping them turning green and becoming poisonous.

When to harvest potatoes

The time to harvest potatoes depends on when they were planted and the conditions in which they’ve been grown.

  • First earlies are usually ready for harvest in June or July, when the flowers are open. These hen’s egg-sized potatoes are best eaten fresh.
  • Second early and salad potatoes should be ready to dig in July and August.
  • Main crop can be harvested from late August to October, once their leaves have yellowed.

How to harvest potatoes

For potatoes planted in trenches or holes, carefully drive a fork or spade into the side of the trench under the plant and slowly raise it to reach the potatoes. With tubers growing under polythene, remove the covering and carefully dig under the plant to expose the crop.

Allow maincrop potatoes to sit on the soil for a brief period to allow them to dry and encourage their skins to harden before being stored, although leaving them in the light too long could turn their skins green.

Things that can spoil your crop

  • Frost can kill or arrest the growth of young shoots. Pay attention to earthing up and cover young plants with a double layer of horticultural fleece if late frosts are forecast.
  • Potato blight thrives during periods of warmth and humidity in July and August and some areas are especially prone to it. Opt for varieties bred to be more resistant to blight or stick to first earlies that should be ready to harvest well ahead of the time of year when this fungal problem can strike. The symptoms of blight are brown patches on leaves and stems, all of which should be removed immediately to protect the disease travelling down to the potatoes.

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