Earthing Up Potatoes

Back in March we started to chitting our potatoes ready for planting on Good Friday, and then the Beast for the East arrived and the soil that had been warming up turned to a block of ice. We know that is hard to believe after five weeks of blazing sun and no rain but winter did bite back, spring did come late and summer has come in with a cricket bat and a taste for wildfires. This year we decided to stop planting in open ground and tyres, and have opted for potato sacks. For those of you who do not know what a potato sack looks like, it looks like this:

potato sacks

They're under the window in a row of eight. These sacks mimic the spread and depth that potatoes have in open ground but without the back breaking digging up, and with my back that is an added bonus. You don't have the additional problem of missing potatoes in the soil and getting a crop in the wrong place the following year. The reason potatoes clean the soil is simple, it's all the digging that comes with planting, earthing up and harvesting. Planting in potatoes sacks is so easy that a seven year old can do it with their eyes closed making whooshing noises like a UFO and laser sounds when they bomb the soil from a far. To prove that theory, you can see step by step how to sow spuds in a sack in an earlier post, hosted by D. Today, we're looking not at pretending to be invading aliens but how to earth up in potato sacks.

Potato growing

Earthing up is straight forward, you will need a good organic compost, we are using Dalefoot here mixed with our own garden compost at a ratio of 50:50. We do this so the mychorriza and bacteria found in our own garden acts as an immune system for the growing potatoes, or to put it in a very basic way, the soil tells the plants that they are 1330ft above sea level, and it can get hot here, it can get windy, it can be very wet. If you don't believe this 'conversation' is happening between your soil and plants, you are very wrong, but that's another post, for another day. Anyway, back to that 50:50 mix. As potatoes grow they form green foliage, called haulms (the foliage of peas and beans are also called this too), if you let the haulms grow and do not earth up (the act of burying the haulms) then your final harvest of spuds will not be large and could have a high proportion of green potatoes. You must never eat green potatoes, the green is chlorophyll (remember that from GCSE Biology?), and as the potato produces this, it also produces solanine. Solanine will make you sick, causing stomach cramps and intestinal problems - basically, you will vomit and blast over a five bar fence. You may have eaten bits of green potatoes before and nothing has happened to you and you're thinking. 'Go away, you silly little man. I know better'. Well, this silly little man knows the botanical name for potatoes is Solanum tuberosum and they are in the Solanaceae family, this includes tobacco, tomatoes and chillies but also includes Atropa belladonna, Deadly Nightshade. An apple doesn't fall far from a tree, neither do plants in the same family. The haulms will sometimes produce fruits after flowering, please take these off (they look exactly like green tomatoes) as these are poisonous like the green potatoes. Basically, if we did not cultivate potatoes and earth up, they would kill us. There are many varieties of potatoes today that are poisonous but are still eaten by people living at high altitudes, how do they get rid of the poison? They allow their potatoes after harvest to freeze solid, this destroys the solanine cells, and the potatoes are then dried. This produces a crop that can be stored for years and you thought the odd nibble on a green crisp was dangerous!

Potato growing on a patio

The act of earthing up reduces the risk of green potatoes and as the haulms are buried, they produce more potatoes along their length. Deeper the bag, greater the yield. This brings us to the problem with open ground production, the waste of water. Potatoes need a lot of water and when you earth up in open ground you produce natural gullies between the rows. These can be flooded and should be flooded when the potatoes are flowering, this is when the potatoes underground are starting to swell. However, a lot of water is wasted in run off. Growing in bags means we can catch the run off in a tray and use it to water other plants. We need to do that this year, five weeks and no rain. The earthing up routine is easy in bags, as the haulms grow, top up  the bags with the 50:50 mix until the haulms are nearly buried, don't worry if you bury them completely as the haulms will push on through, you aim to leave around an inch (5cm) of haulm above the soil and keep doing this until the bag is three quarters full - this leaves room for that flooding you would do in the gullies between open ground potatoes. Keep watering those potatoes regularly, in this weather they will need plenty of water. 

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