Root cellar potato storage, Mother Earth News post on hot weather seed germination tips

Potato harvest.
Photo Nina Gentle

We harvested our March-planted potatoes 21 days ago, and we are in the process of sorting them and managing conditions in our root cellar to cure the potatoes and help them store well.

Here are our “Root Cellar Warden” instructions:

  1. Before the potato harvest, leave the cellar open for a couple of days to warm up to the temperature of the potatoes (to reduce condensation and rot.)
  2. Gather crates. We store our potatoes in open plastic crates on plastic pallets, which allow ventilation but not rotting or holding of fungal spores.
  3. Like most root vegetables, potatoes store better if they are not washed before storage.
  4. In summer we stack the crates of harvested potatoes under tree near the cellar the first night, to lose some heat. At dusk, we cover them with a tarp to keep dew off and keep them dry. At 6 or 7 am next day, we put the crates in the cellar and close the door.
  5. Store in a moist, completely dark cellar, avoiding excess moisture.
  6. After the harvest, the potatoes need a surprisingly warm temperature, 60-75°F (15-25C) with good ventilation, for two weeks of curing. This allows the skins to toughen up, cut surfaces to heal over, and some of the sugars to convert to the more storable starches. Wounds do not heal below 50F (10C).
  7. In June/July, after harvesting the March-planted potatoes, we leave the door open at night almost every night for a week, then every other night, and close it early in the morning. After the Oct/Nov harvest of the June-planted potatoes, we leave the door open on mild nights or days every 2 or 3 days, and close it later. (It’s easier to cool the cellar in the fall.)
  8. As well as cooling to a good storage temperature, for the two weeks between harvest and sorting, the root cellar needs 6-9 hours of ventilation every two or three days. The potatoes are still “alive” and respiring, and will heat up if left closed in. If not ventilated, the potatoes get Black Heart. This is a dark hard black nodule of dead cells in the middle of the potato. Ventilate when the temperature is 0-20 Fahrenheit degrees (0-11 Celsius degrees) cooler than the goal:
  9. Air in the daytime if nights are too cold and days are mild;
  10. Air at night if nights are mild and days too warm.
  11. Try hard to avoid having the cellar cool down, then warm up. This causes the potatoes to sprout.
  12. Ventilate more if it is damp in there.

    Sorting potatoes .
    Photo Wren Vile
  13. After two weeks, the potatoes need sorting to remove Use First and Compost ones, keeping the varieties separate. Usually we bring the crates out to the top of the cellar steps in rotation. We gather buckets, rags, gloves. It’s important to do this 14-21days after harvest, and not leave it longer, to minimize the spread of rot.
  14. We find that if we do this one sorting after two weeks, we don’t need to check them any more after that – pretty much anything that was going to rot has already done so. Very little additional rotting occurs after a two week curing and sorting. If left unsorted for longer, rot does spread. If we sort too soon, we miss some potatoes with tiny bad spots, and need a second sorting.
  15. Restack the crates in the cellar, remembering to leave an airspace between crates and walls.

    Crates of potatoes in our root cellar.
    Photo Nina Gentle
  16. For weeks 2-4, the temperature goal is 50°F (10C), ventilation is needed about once a week.
  17. After week 4, ventilation for air exchange is no longer needed, as the potatoes are now dormant. We want to cool the cellar whenever a cool, mild night or chilly day is forecast, to 40-45F (5-7 C) if possible in late fall, and as close to that as we can get, in summer. (In summer, potatoes can be stored at 60-75F (15-25C) for up to six weeks – but at higher temperatures they will sprout.)
  18. Avoid wildly fluctuating temperatures, as the stress can cause “physiological aging” which among other things, inclines the potatoes towards sprouting.
  19. Continue to ventilate as needed during times of cool temperatures, to maintain the cellar in the ideal temperature range.
  20. Avoid storage much below 40F (5C), as these low temperatures will cause some of the starches in the potatoes to turn to sugars. This gives the potatoes a strange taste, and will cause them to blacken if fried. Potatoes which have become sweet can be brought back to normal flavor by holding them at about 70F/21C for a week or two before using.
  21. With a good in-ground root cellar, potatoes can be stored for 5-8 months. As a sustainable alternative to refrigerated or electrically cooled storage for crops needing cool damp conditions, traditional root cellars are a good option.

    Potato crates in our cellar.
    Photo Nina Gentle

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Dormancy Requirements of Potatoes

We are researching the dormancy requirements of potatoes in an effort to store ours so they don’t sprout when we don’t want them to! So if you have information on that, please leave a comment

What I know so far about dormancy is that potatoes need a dormancy period of 4-8 weeks after harvest before they will sprout. So if you plan to dig up an early crop and immediately replant some of the potatoes for a later crop, take this into account. Get around this problem by refrigerating them for 16 days, then chitting them in the light for 2 weeks. The company of apples, bananas or onions will help them sprout by emitting ethylene.

To avoid sprouting, keep the potatoes below 50F (10C) once they are more than a month from harvest, avoid excess moisture, and avoid “physiological aging” of the potatoes, caused by stressing them with fluctuating temperatures, among other things.

Potato Sprouting Conditions

The rate of growth of sprouts on potatoes is directly related to the degree-days above 40F/5C, so storing potatoes above 40F (5C) (for best flavor), clearly runs the risk that at some point they will start sprouting. If eating potatoes do start to develop sprouts, it’s a good idea to rub off the sprouts as soon as possible, because the sprouting process affects the flavor, making them sweet in the same way that low temperatures do.

Seed potato pieces after pre-sprouting for planting.
Photo Kati Falger

If you are storing potatoes for seed, and have good control over the temperature of your cellar, you can manipulate the conditions somewhat to help get best yields. The “physiological age” of the seed tubers affects both the early yield and the final yield. Cold storage conditions – below 40F (5C) keep the seed “young”, which leads to a crop that takes longer to mature. Avoid planting physiologically “young” seed potatoes unless you are prepared to harvest later than usual (or have a lower yield when you bring the crop to an end by mowing). “Old” seed gives an earlier harvest, but perhaps a lower final yield. If you will be planting in spring for an early finishing crop, “age” your seed potatoes by storing them at 50F (10C) until two weeks before planting, then harden off at a lower temperature to reduce thermal shock when they reach the soil. “Middle-aged” tubers stored at 40-50F (5-10C) give the highest maincrop yields. When we buy seed potatoes we have no control over the storage conditions before we get them, and probably no information either. The physiological age can be estimated by the length of the longest sprouts on the tubers. The best information I have found about potato storage and sprouting is in a book from the UK: The Complete Know and Grow Vegetables by Bleasdale, Slater and others.

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I wrote an article about growing potatoes for Growing for Market magazine.

I also wrote about root cellars for potatoes and other vegetables in Sustainable Market Farming and forGrowing for Market magazine in November 2008.

Storage is not a one-solution-fits-all project. Produce for storage might need to be frozen, refrigerated, cool, warm, moist or dry. Refrigerators and the ingenious CoolBot have their place. Mike and Nancy Bubel, in their excellent book Root Cellaring identified five different sets of storage requirements. Since their book was published, more evidence suggests that potatoes are better stored at 40-50F (5-10C) than 32-40F (0-5C), and that cucumbers and eggplant, like peppers, are better above 45F (7C).

Ethylene. Ripe fruits and actively growing plants (such as sprouting potatoes), emit ethylene, which then promotes more ripening or sprouting. Ethylene-producing crops need to be stored separately from those sensitive to ethylene – vegetables you don’t want to sprout, such as onions and potatoes.

Other Vegetables in Cellars. Most other root crops can also be stored in a root cellar. Some people pack the unwashed vegetables in boxes of sand, wood-ash, sawdust or wood chips. Perforated plastic bags are a modern alternative. Whole pepper plants can be hung upside down in the cellar, as can headed greens, like cabbage. Or cabbage can be replanted side by side in boxes or tubs of soil. Celery and leeks can also be stored by replanting in the same way. I’m more of a fan of choosing hardy varieties of leeks and leaving them out in the garden for the winter, but this is zone 7 and people in places with really deep snow or very cold winters might laugh ruefully at that suggestion.

Root Cellar Construction

Mike and Nancy Bubel Root Cellaring contains great designs and instructions for excavated root cellars, including a two-room version for keeping different crops at different temperatures and humidities. Excavated root cellars are not the only possibility, but they have advantages because the earth insulates the cellar. Because soil is heavy, in-ground cellars must be strongly built, and well drained, so that water does not pool, freeze in winter and crack the walls. The book has details about laying out the site, working with concrete blocks, mixing concrete, making a supported roof, and drainage.

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20 Tips for Success in Germinating Seeds in Hot Weather

This is the title of my newest post on the Mother Earth News Organic Gardening Blog. In my previous post I wrote general themes for starting seeds in hot weather. This time I listed 20 specific tricks under categories such as Seed Storage, Sowing Seeds Indoors, Sowing Seeds Outdoors, Watering, Soaking Seeds, Pre-sprouting and Fluid Sowing.

Good irrigation is important for successful carrot growing in hot weather.
Photo Bridget Aleshire

Ordering seeds! Seed Viability and Varieties New to us

I’ve been busy putting our seed orders together. As we grow so many different crops, it’s quite a time-consuming process. And I hate to buy too little and be out in the field on planting day, looking at an almost empty packet. Equally, I hate to buy too much, which either wastes money (if we throw the extra away), or else causes us to risk sowing seed that really is too old, and won’t do well. I keep a chart of how long different types of seed last:

Seed Viability

(From Sustainable Market Farming, (c) Pam Dawling, New Society Publishers, 2013)

     

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   “Opinions vary a bit about how many years seeds of different vegetables are good for. The fuller story is that storage conditions make a big difference. You can make your own decisions, weighing up the information supplied, your knowledge of how carefully you stored the seeds, the information on each packet about percentage germination when you bought it, and the economic importance to you of that particular crop. If you always transplant lettuce, as I do, you can risk one of your four varieties in that sowing coming up poorly, and just plant out more of the other three if it fails. Many seed catalogs include information about seed longevity, and so does Nancy Bubel in The Seed Starters Handbook.

www.chelseagreenFrank Tozer in The Organic Gardeners Handbook has a table including minimum, average, and maximum.

A simplified version is as follows:

  • Year of purchase only: Parsnips, Parsley, Salsify, and the even rarer Sea Kale, Scorzonera
  • 2 years: Corn, Peas and Beans of all kinds, Onions, Chives, Okra, Dandelion, Martynia,
  • 3 years: Carrots, Leeks, Asparagus, Turnips, Rutabagas
  • 4 years: Spinach, Peppers, Chard, Pumpkins, Squash, Watermelons, Basil, Artichokes and Cardoons
  • 5 years: most Brassicas, Beets, Tomatoes, Eggplant, Cucumbers, Muskmelons, Celery, Celeriac, Lettuce, Endive, Chicory.”

Rather than deteriorating with age, some very fresh seed has a dormancy that needs to be overcome by chilling (lettuce). Other seed contains compounds that inhibit germination. These can be flushed out by soaking in water for about an hour (beets).

Another of the challenges with seed ordering is converting between grams, ounces and seed counts. Here’s a helpful table of 1000 Seed Weight for 13 crops.

Our main seed suppliers are FedcoJohnny’s and Southern Exposure. Fedco has great prices, especially on bulk sizes, great social and political commentary in the catalog, and no glossy pages. Johnnys has some good varieties that Fedco doesn’t, and a ton of useful information tucked away on their website. Southern Exposure is best on southern crops and heat tolerant varieties which we can’t expect seed companies in Maine to specialize in. Plus, SESE are my friends and neighbors.

This year we are trying some new varieties. Generally we like to have some reliable workhorses that we know well, and trial a few new things, especially if we hear our favorite varieties are no longer available. Last year our Nadia eggplant couldn’t cope with the heat. For a while in early summer they didn’t grow at all – no new flowers, never mind new fruit. So next year, alongside Nadia I’m trying 3 that should deal better with heat. Florida Highbush is open-pollinated, from the Seed Savers Exchange. Epic and Traviata are hybrids from Osborne Seeds.

Epic eggplant from Osborne Seeds
Epic eggplant from Osborne Seeds
Traviata eggplant from Osborne Seeds
Traviata eggplant from Osborne Seeds
Florida High Bush eggplant from Seed Savers Exchange
Florida High Bush eggplant from Seed Savers Exchange
Sugar Flash Snap Peas from Osborne Seeds
Sugar Flash Snap Peas from Osborne Seeds

I also bought some Sugar Flash snap peas from Osborne. We have been big fans of Sugar Ann, but I’ve heard Sugar Flash is even better on flavor, yield and harvest period. We’re going to find out!

For a couple of years we really liked Frontier bulb onions as a storage variety for this climate and latitude (38N). Frontier disappeared from the catalogs of our usual suppliers and we tried Gunnison and Patterson. This year – no Gunnison! And we didn’t get a good test of Patterson last year, as we failed to weed our onions enough, after an initial enthusiastic good go at it. We were looking again at Copra, one we grew some years ago (before we found Frontier). I lucked out when I decided to see if Osborne had Gunnison, while I was shopping there. they didn’t, but they had Frontier! And then when I was shopping at Johnny’s, I found they did have some Gunnison for online sales only. So I ordered those too!

We’re also trying Sparkler bicolor sweet corn from Fedco and a drying bean I won’t name, as the seed is in short supply. And this year we’re hoping Red Express cabbage will prove to be a reliable little worker. We used to like Super Red 80, but had several years of poor results. Since then, none of the other red cabbages we tried have satisfied us in terms of size, earliness, productivity and flavor.

West Indian Gherkin Seeds (Cucumis anguiria) from Monticello
West Indian Gherkin Seeds (Cucumis anguiria) from Monticello

After a few years of poor pickling cucumbers, we’re going outside the box and trying West Indian Gherkins from Monticello, where they were grown by Thomas Jefferson (and some of the enslaved people, no doubt). These are not closely related to actual cucumbers, but are used similarly. I saw them growing in the Monticello garden when I was there for the Heritage Harvest Festival in September, and they are certainly robust and productive in hot humid weather. We’ll see how the pickles turn out!

My only other “impulse buy” was the Salanova Lettuce new at Johnny’s. They are 6 varieties of head lettuce designed to be used for salad mix at a single cutting. Quicker than  snipping rows of baby lettuce with scissors. More fun than plain lettuce heads. They are loose heads of small leaves in various shades of green and red, and two “hairstyles”: frizzy and wavy.

Salanova Lettuce from Johnny's Seeds
Salanova Lettuce from Johnny’s Seeds