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How to Build an Underground Root Cellar : Prolonging Your Harvested Crops

How to Build an Underground Root Cellar : Prolonging Your Harvested Crops

A Root Cellar will be the perfect storage system for harvested root vegetables. Root Cellars are cold damp rooms. Root Cellars are not suitable for the Squash family and the Onion family, which need to be kept in a dry cold room.

Root Cellars were popular before refrigeration as it was the only way to keep your hard earned harvest fresh during the winter and into the next Spring.

1. Where and when shall I build my DIY Root Cellar?

It wouldn’t be much fun to dig a root cellar when the ground is frozen. The best time to build one is in April. You could build one right up to harvest but it’s recommended to test the temperature and humidity during the warmer months in preparation. After all, the whole purpose of the Root Cellar is to keep your harvest cool during the warmer months.

When selecting a place for your Root Cellar, choose a position away from any trees. This is important as tree roots will eventually grow through and crack your Root Cellar walls.

Choose a position where you know there is definitely a good 3 meters of earth beneath your feet and no pipelines or cables. Also, if possible, choose a shaded area of land, but remember, not near the trees.

2. Digging out the Root Cellar: 3 meters deep

For an underground Root Cellar, you will obviously need a spade. Depending on how big a space you were aiming for, maybe hire a small digger.

Most Root Cellars are built of wood, stone, slates or cement bricks. Metal isn’t recommended due to rapid heating and cooling.

The best way to construct your underground Root Cellar is to think of a box without a bottom. You will need to use cement bricks or wood planks. (Think WW1 trenches, think bunker). This will keep the earth from piling in once you have dug the capacity space that you require. Complete temperature stability is reached at 3 meters deep.

As long as the ‘box’ is underground, it doesn’t matter what shape it is, it could be triangular if you fancy, or round. The main attention at this point is making it earth tight and at no risk from collapse.

3. So what next? Access and storage

You have created a lovely shaped hole in the ground. It now needs a roof and door and a ladder. Some people like to create a trap door style roof with a ladder leading down, house cellar style. Some people are more creative and create ‘hobbit’ style houses above ground that have porches at ground level before leading down into the cellar.

Wood would be the preferred choice for a door. Metal would be disastrous as the sun would heat it and therefore raise the temperature of the Root Cellar.

Shelves are recommended to place the harvested vegetables on. However, and very importantly, do not place shelving flush against the cellar walls. This could create damp and mildew to form due to trapped air and the high humidity levels. Leave at least 8cm between any wall or shelf.

Flooring is needed. Traipsing through rough earth is not very practical. The best floor for a Root Cellar is just tightly packed earth but if that horrifies you, you can use concrete slabs.

4. How to monitor the temperature and humidity

A Root Cellar needs to keep a temperature of 32F to 40F at all times. It is this temperature that halts the decomposition of the vegetables by slowing down the fermentation process that naturally happens to food once picked.

Humidity of 85% to 95% is also a must. Vegetables have a high water content and the high humidity level in the Root Cellar prevents the loss of moisture through evaporation. Think sun dried tomatoes. They shrivel after being left in the sun. The Root Cellar does the opposite and keeps the moisture in.

Monitoring the temperature and humidity levels can be easily done with a hygrometer. These are cheap and can be bought for less than $10. Maybe get two, one for each end of the Root Cellar, to monitor any drafts or cracks in the walls.

And finally, the Root Cellar needs an air pipe vent. Use a drainpipe so that any gases that build up can escape and fresh air can ventilate and cool the Root Cellar.

5. Ready for harvest?

Harvest potatoes

Root vegetables, fruits and brassica can go into your new Root Cellar. However they all have a different shelf life.

These are:

  • Broccoli and Parsnips – 1 month
  • Pears and Radish – 2 months
  • Leeks, Cabbage and Beets – 4 months
  • Apples, Carrots, Turnips, Potatoes – 6 months

Keep all fruits separate from vegetables. They give off different gases. It would be practical to have a fruit area one side and a vegetable area the other side.

6. So, what should I do with my Squash and Onions?

Harvest pumpkins and gourds

These types of vegetables need to be kept in a dryer humidity of 60-70% and at a temperature of 50-60F. The best place to store them is in a pantry with your tinned foods, an unheated under stairs area, a garage or an outbuilding, but check the best place in your property to store them with a hygrometer first.

Most importantly the temperature needs to be constant. Placing them on wooden shelves or in wire baskets in your chosen area will suffice. Squash should last 6 months and Onions and garlic up to 8 months.

If you have the space and the dedication to produce enough crops to fill your Root Cellar each year, then go ahead and build one. Make it as plain or as fancy as you desire. If you monitor the conditions and store the crops correctly, you should have tasty crops to eat right into Spring.

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