Largest Yield from One Seed Potato Competition

It’s an old competition on allotment sites – who can get the biggest yield from a single seed potato? It may have started in the second world war or even before, certainly it was common in the 1950’s.

The secretary or whoever is running the competition selects seed potatoes as near to each other as he can get and each contestant gets one. On a chosen harvest day, whoever has the heaviest crop is the winner. Simple!

Yields ranged between 10 kgs and 40 kgs but some growers had the magic touch for a lot more. Apparently a hundredweight (112 lbs or 51Kg) was often achieved! I’ve never had a go myself but my father-in-law told me about the competitions he’d been in and how it was done.

How many potatoes can you get from one seed potato?

Chit the seed potato and prepare the ground

Start by chitting the seed potato as normal. Whilst that’s chitting, prepare the ground. Apparently well-rotted horse manure is the magic ingredient although cow will do. Add copious amounts – a heaped barrow load per square yard. Work it in well and mix it thoroughly.

If it’s a heavy clay soil, add gypsum at 8 oz. per square yard. Gypsum has a similar effect to lime but doesn’t increase the pH as lime does. Potatoes like a lower pH than most vegetables – 5.5 to 6.0.

Ideally you want a high potash content in the soil which you could achieve by adding wood ashes. Wood ashes do have a little lime but not enough to really worry about. The level of potash in wood ashes varies a lot so perhaps better to add an ounce per square yard of sulphate of potash.

The soil needs to be really friable and open as well as rich in organic matter for at least a foot deep but 18 ins. is better if possible. It needs to feed the crop and hold plenty of water but not be waterlogged so the potatoes drown.

Pots or Soil?

You can grow your competition crop in pots if you prefer but pot or sack growing is trickier. One slip-up with watering and you can lose the plants or dramatically reduce yield.

Another problem with pot growing is that the pots may get too warm. If the temperature rises above 24ºC the plant will stop forming tubers and put its energy into forming seed heads and haulm instead.

However, best yield from one potato competitors usually started the crop off in pots.

Cut the seed potato

Cutting seed potato to get more shoots – photo courtesy Medwyn Williams

Back when times were hard and seed potatoes in short supply, cutting seed potatoes to increase the yield was normal practice. Usually they were just cut in half lengthways through the rose end thereby giving shoots in both halves.

This time we want to divide the seed potato into as many parts as we can so long as each piece has a sprout coming from an eye. We want to give each sprout as much potato as we can to give it the energy to grow, so a lot of care and attention at this stage will pay dividends. If you’ve not done this before, practice on another seed potato before going for it. Use a sharp knife for clean cuts.

Once cut, dab the cut edges with kitchen roll place the cut tubers skin side down on a tray so the cut faces dry out. You’ll probably get 6 or even 8 pieces from the one seed potato. Leave for a day or two so the cut faces are dried off.

Start in pots

Rather than plant out directly at this point, start the potatoes off in 6 ins. pots in a multi-purpose compost with added nutrients. Assuming we’re still in very early spring and the weather is still cold, the pots should be in a greenhouse, coldframe or even on a window sill indoors. Ideal temperature is 15º to 20º C

Once the plants are putting up foliage, use some of it to strike cuttings in pots. Remember with cuttings:

• Cleanliness is essential. The warm humid environment that the cuttings need is ideal for disease and fungal growth. Clean knives / secateurs well, dip in methylated spirit and allow to dry. Wash pots carefully using diluted Jeyes Fluid.
• Use a 50:50 mix of perlite and multi-purpose sterilised compost.
• A commercial rooting powder such as Bayer Strike-2 or make your own hormone rooting compound from willow will help quickly develop the root system
• Plant one cutting per 3 ins pot for this
• The cuttings should be kept humid but not overly wet.
• Keep the cuttings in a propagator to keep the humid atmosphere or us a plastic bag over each pot.

Spray chitting potatoes and the pot growing plants with seaweed solution fortnightly. Plant out, hardening off if necessary, when established and weather allows.

Planting out

You’ll know at this stage how many plants you have from your single tuber so you’ll know how much space to allocate in your competition bed. Cover this area with fleece, black plastic or cloches to warm up the soil. Every little helps and a couple of degrees can make a surprising difference.

Space the plants a little wider than normal, for an early potato that would be 15 ins apart instead of 12 ins in rows 2 feet apart. There should be no weeds in the soil – weeds will compete with the crop and reduce yield.

Cultivation

Earth up the potatoes as normal as you go along. If the weather is cold, use fleece to keep the plants warm. Conversely, if a heatwave should arrive provide shade. Check frequently if the soil is drying out and water as necessary. Potatoes use a lot of water and if they don’t have enough yields will fall considerably. Keep weed free.

Check out the pages on How to Grow Potatoes for more information on general potato growing.

Feeding

The manure added initially should be feeding the plants but some extra fertiliser won’t go amiss. Use a specific potato fertiliser. Alternatively and possibly even better, use a liquid tomato feed weekly. This could be a commercial feed or home made comfrey liquid.

Harvest

Don’t harvest early – every day if not every hour counts. Be careful not to miss any tubers, even the tiddlers, every ounce counts.

Can you help?

If you’ve experience of growing the most from a single seed potato, do pop your tips in the comments.