Root Crops in October

Radish Quick Pickles
Photo by Bridget Aleshire

Root Crops to Plant in Central Virginia in October

We have now passed our last chances to sow root crops outdoors. But the exciting season in the hoophouse has just begun. In early October, we sow radishes in our hoophouse. See Root Crops in September for more about our succession of hoophouse radish sowing dates. We like Easter Egg (a multi-colored mix of red, plum, pink, purple and white varieties, that matures over several weeks), Cherry Belle, the fast, uniform red globes, and White Icicle, like baby daikon about 3” (7 cm) long. These three varieties all stay crunchy and tender. We have a dread of fibrous radishes! Most years we make a sowing at the beginning of October and another at the end, and these will feed us from early November until early February. The late October sowing lasts for 8 weeks, so it’s good to make sure we plant enough. Radishes do a lot to brighten up meals in December and January!

White Egg Turnips.
Photo Southern Exposure Seed Exchange

In mid-October (10/10-10/25), we sow our first of three plantings of hoophouse turnips. We like the very fast-growing and tender Hakurei hybrid. It has short hairless tops which also make good eating. We sow this variety on the south side of the bed, leaving the other 3 rows for the taller varieties. We also like Early White Egg and Oasis, which are not quite as uniform as Hakurei, but are OPs and the seed is much cheaper. They produce more greens, which we value too. In the north row we often grow Red Round, a beautiful red-skinned turnip with tall attractive leaves. We also like Scarlet Ohno Revival, which has the advantage of hairless leaves. This is an Open Source Seed Initiative variety. The OSSI pledge: “You have the freedom to use these OSSI-Pledged seeds in any way you choose. In return, you pledge not to restrict others’ use of these seeds or their derivatives by patents or other means, and to include this pledge with any transfer of these seeds or their derivatives.”.

We thin the turnips as needed. If we sowed thickly, the first thinnings become baby greens for salad. Once the turnips are the size of marbles, we like to thin the plants to 3” (7 cm) apart and cook them whole, roots and greens together. The next thinning is to 6” (15 cm) and from that point on, we harvest the greens and roots separately. We get a ratio of one bucket of roots to two buckets of greens, which fits our needs perfectly. We like to mix the roots, as the one quarter of red roots adds a pop to the appearance.

Root Crops to Harvest in Central Virginia in October

Misato Rose Winter Radish.
Photo Southern Exposure Seed Exchange

We can continue harvesting beets (and beet greens), carrots, horseradish, kohlrabi, radishes, turnips (and turnip greens), and winter radishes outdoors. Once we have had a decisive frost we can harvest parsnips – the frost really improves the flavor. Our 9/6 sowing of hoophouse radishes will start to mature.

See Washing, sorting and storing root crops in Root Crops in September

We tackle our process of clearing root crops and storing them, starting with celeriac (if we grew it this year). We start with the least cold tolerant roots and work our way to the most cold tolerant. This list is root crops only. See my list of Winter-Kill Temperatures of Cold-Hardy Winter Vegetables 2020 for a more complete picture of “Harvesting in Time”

Clear and store (in this order):

  • Sweet potatoes 50°F (10°C)
  • “White” Peruvian potatoes 32°F (0°C) approximately
  • Celeriac 20°F (°C)
  • Turnips 20°F (°C)
  • Winter radish 20°F (°C)
  • Beets 15-20°F (°C)
  • Kohlrabi, 15°F (°C)
  • Carrots 12° F (°C)
  • Parsnips 0°F (°C)
Bucket lid with holes for sorting root vegetables for storage.
Photo Wren Vile
  • Wash, and store roots in perforated plastic bags in refrigerator or root cellar. We use a special measuring bucket lid to help new workers determine if roots are big enough to store.
  • Harvest sweet potatoes before soil temperatures go much below 55°F (13°C), or night air goes below 50°F (10°C). See the Special Topic below.
  • Harvest white potatoes when the skins have thickened. (When the skin is undamaged after rubbing two together. About 2 weeks after the  tops die). See Harvesting Potatoes and Root Crops in June. Two or three days before harvesting, we spend the day removing the hay mulch from our 1600 row feet (488 m) potato patch to the compost area. Our potato digging machine can’t deal with mulch or heavy weeds. To fit with using machinery, we clear complete rows. We have a Perfect Potato Harvest Checklist. For fall harvesting we do the tractor work in the morning and pick up the potatoes in the afternoon, avoiding leaving any out overnight if it will be frosty. (When harvesting the March-planted potatoes in July, we do the tractor work early in the morning and start picking up the potatoes as soon as possible. We aim not to be outdoors after lunch when it’s hot, but if we need to, we will, as we don’t want ready-baked potatoes sitting on the soil!) Tractor time is 4 hrs x 2 people. Picking time is 30 people-hours.
  • For beets, we allow 6 people-hours per bed (360 row feet (110 m), and expect 2-3 50-pound (23 k) bags per bed. Cut the stems about ¼” (6 mm) above the root, to reduce “bleeding” when you cook the beets. I was reminded recently that not everyone knows that the easiest way to cook beets is to scrub them, boil them in the skins, drain and immerse in cold water, then simply slide the skins off. Hardly any wasted food and no wasted time.
  • Bucket of freshly harvested Detroit Dark Red beets for storage.
    Photo Pam Dawling
  • For carrots, we allow 4.5-6.5 people-hours per (large) garden cart for washing, trimming and sorting. Plan to keep the last 15 minutes for clean-up. Divide the rest of the time available by 3. Use 1/3 of the time for digging, 2/3 of the time for washing and sorting. Add time to take to storage. Record yields. We take the carrot tops back and spread them across the beds. (fall harvest only ). In the spring and summer we take carrot tops to the compost pile, as the smell can attract carrot rust root flies. In late fall it is too late to sow cover crops to protect the soil, and the flies have gone to overwinter wherever they do that, so we spread the tops over the beds to provide some protection for the soil.)
Carrot rust fly damage (or possibly carrot weevil) Photo Jessie Doyle
Carrot pest larvae: carrot rust fly I think. Maybe carrot weevil.
Photo Jessie Doyle

Special Root Crop Topic for October in Central Virginia:

Harvest sweet potatoes

Here’s our method:

First roll up the drip tape. Harvest on 3 mild days – generally in the week that your first frost usually occurs (10/7-14). We expect our whole harvest of 800 row feet (244 m) to take 80 people hours. Allow 1/3 of the time for snipping, 1/3 for digging, 1/3 for crating and schlepping. Digging takes a bit less time than either of the other jobs. Even a few hours exposed to temperatures below 50°F (10°C) will cause chilling injury. (Frost on the leaves does not of itself damage the roots). Don’t leave clipped plants uncovered overnight. Don’t leave sweet potatoes outdoors. Clip the vines, dig carefully, set the tubers in plant-clusters to dry on the soil. Select seed tubers (healthy med-size tubers from high-yielding plants, no rat-tails).  We save a generous 100 Georgia Jet, 100 Beauregard, 20 each of Bill Shane’s White and Jubilee. (These last two are unofficial names for varieties we were given and are maintaining for genetic diversity.)

Sweet potato harvest.
Photo Nina Gentle

Other Root Crop Tasks in Central Virginia in October:

Curing sweet potatoes and white potatoes

Cure sweet potatoes in collapsible, stackable holey crates (or in wooden flats with spacers for ventilation) and cover with newspaper on top, in a basement with the heater on, for 10-14 days (85-90°F, 27-32°C, 80-90% humidity) or longer if it’s cooler and drier.  Use fans. Splash water on floor. Curing is complete when the skin is undamaged after rubbing two together. Restack the boxes (in a rodent-proof storage cage, if you are using an outbuilding).

Cure freshly harvested white potatoes in a root cellar at 60-75°F (15.5-24°C) for 2 weeks, with good ventilation, then cool cellar to lower temperature. See Special Topic for July. For weeks 2-4, the temperature goal is 50°F (10°C), and fresh air is needed about once a week. Our method of providing an air change in our cellar or adjusting the temperature is to leave the door open when the temperature will be closer to our goal than the current reality. It works well enough.

Harvesting potatoes

Harvesting potatoes and sorting storable from others.
Photo Nina Gentle

Harvesting potatoes

This is the fourth part of a monthly series on growing potatoes, a dietary staple.

PART ONE: Planting potatoes (April)

PART TWO: Growing potatoes (May)

PART THREE: Potato pests and diseases (June)

PART FOUR: Harvesting potatoes (This one, July)

PART FIVE: Storing potatoes (August)

PART SIX: Planning to grow potatoes again (September)

I have a whole chapter about potatoes in Sustainable Market Farming, where most of this information can be found.

See Root Crops in June for info on digging up new potatoes, if you can’t wait for them to mature! Harvest for immediate use anytime you’d like after the tubers reach a big enough size.

Picking up lifted potatoes and crating them.
Photo Nina Gentle

Preparing for potato harvest

When the leaves start to turn pale, the plant has finished its leaf-growing stage and will be putting energy into sizing up the tubers under the ground. Avoid irrigating at the end of the growing period or the potatoes may develop hollow heart, make knobby secondary growths or even crack. For maximum yield, and to harvest for storage, wait until the tops are completely dead.

In England, we planted in spring and harvested in October, waiting for the frost to kill the vines. In Virginia, we plant in March and June, harvesting in July and October. For our unmulched March-planted July harvest, we mow two weeks before our planned harvest, to fit a tight crop turnaround. In hot weather the cut tops and weeds dry up. If more weeds grow, we mow again the day before harvest. For our fall-harvested crop, planted and mulched in June, we need to remove the mulch after the mowing and before the harvest. This is a slow job, but necessary, and the mulch makes a good addition to our compost pile. If it looks like rains will delay the harvest, or nights are forecast to be very frosty, we delay de-mulching until the day before harvest.

Varieties such as Red Pontiac, Yukon Gold and Kennebec are determinate — they grow as a bush, then flower and die. If you have indeterminate varieties such as Russet Nugget, Nicola, German Butterball or Elba, you will need to kill the vines. I’ll come back to the topic of determinate and indeterminate varieties in Part Six, Planning to grow potatoes again (September). You can bring about an early vine death by mowing or flaming. This will also remove weed growth that could interfere with your digging equipment.

Potato harvest in progress. Note the line up of garden carts to haul away the bounty. Photo Nina Gentle

Whether the vines die naturally at the end of their lifespan, or they die of disease, or the frost kills them, or you do it yourself by mowing or flaming, it helps storability to wait 2-3 weeks more before harvesting to allow the skins to toughen up. They become more resistant to scrapes and bruises) and the potatoes become higher in dry matter. Harvesting is also easier if the vines are well dead. Test by digging up a sample and rubbing the skins. When the skins don’t break, the potatoes are storable.

Be sure to have enough crates, buckets, totes, gloves and workers. Clean and air the root cellar and warm it to 70°F (21°C).

Harvesting your potatoes

If possible, harvest when the soil moisture is 60-80% of field capacity. Not too dry, not too wet. This reduces damage from scraping. Ideally the soil temperature will be 45°-65°F (7°-18°C).  Because soil temperature lags 3-4 hours behind air temperature rise each day, in cold weather, try to harvest late in the day, but with time to finish before dark. In hot weather, harvest in the morning as early as possible. Tuber temperature will also affect bruise and rot susceptibility. Do not harvest when tuber temperatures are below 45°F (7°C) or above 85°F (30°C).

To use our potato digger we have to remove the mulch first.
Photo Twin Oaks Community

We use a Checchi and Magli single-row side delivery SP100 harvester. It does a good job in clean soil and an excellent job in clean fairly dry soil but gets stuck if we have a lot of organic material on the soil (weeds or mulch). The 1-row Potato Digger from US Small Farm Equipment, which a neighboring farm bought, has the same challenge. If using a digger, don’t set it too deep, or too much soil will be dumped on the harvested potatoes.

During harvest, someone walks alongside the tractor with a long-handled hook/claw tool, to clear blockages and hook any potatoes from the path of the tractor wheels. The rest of the crew follows, picking up and sorting the potatoes. If they are wet, we leave them to dry for a short time. We sort the damaged ones into “Farm Use” buckets and crate up the good ones. We try not to leave any potato parts in the field, to reduce the chance of spreading diseases.

When freshly harvested, potatoes are tender, breathing things. Avoid bruising, which is damage that does not break the skin, by not dropping potatoes more than 6” (15 cm), or throwing them towards a container. Don’t bang them to knock off extra soil. In hot weather we aim to work until done and not leave any potatoes in the field baking for long. In cold weather we aim to get done before nightfall and not have any freeze overnight!

Chain of people moving crates of potatoes from the truck to stack under a big pine tree.
Photo Nina Gentle

When harvesting in summer, we stack the crates of potatoes covered with a tarp, under a big tree overnight to lose some of the field heat before moving them to the root cellar early next morning. For the fall harvest, if the weather is chilly, we take the crates straight into the root cellar. Potatoes you take from storage can be no better than the quality of the potatoes you put into storage!

Potato harvesting raises rocks to the surface, so we try to find time soon after the potato harvest to collect them for use in road repairs and construction.

Yields are likely to be 150 lbs/100ft (223 kg/100m); 200 lbs/100 ft (300 kg/100m) or more is a good yield; double this is possible. In my book Sustainable Market Farming, in the potato chapter, I made a mistake and gave these as pounds per acre, which would be a miserable yield! 5 gallon buckets and square plastic “milk” crates hold about 30 lbs each (14 kg)

Post-harvest two week curing

After harvest, potatoes need to cure for two weeks at a surprisingly warm temperature: 60°F–75°F (15.5°C–24°C), and 95% humidity. While curing, the root cellar will need 6-9 hours of ventilation every two or three days. The potatoes are still actively respiring, so they need a good oxygen supply. Failure to ventilate enough can lead to Blackheart, where the inner tissue of the potatoes dies and turns black.

Potatoes will heat up if left closed in. Ventilate when the temperature is 0-20 F° (0-11 C°) cooler than your goal: air in the daytime if nights are too cold and days are mild; at night if nights are mild and days too warm. Try hard to avoid having the cellar cool down, then warm up. That causes the potatoes to sprout. If there is too much condensation, use a fan and open the cellar doors, when temperatures are closest to the goal. During the curing period, the skins toughen up more, and cut surfaces and superficial wounds heal over, enabling long-term storage.

Sorting potatoes in early November.
Photo Wren Vile

Sorting and preparing for long-term storage

After two weeks, we sort through the whole storage crop for rot, We find that this single thorough sorting can remove almost all of the storage problems that are going to happen. Not sorting at this point lets rots spread.

After the curing period, the potatoes become more dormant and do not respire so actively. Fresh air is needed about once a week in weeks 2-4, after which air exchange is not needed. Relative humidity should be 90-95%, to keep weight loss to a minimum, but not 100%! If the cellar is too warm, you will need to ventilate to lower the temperature.

Once potatoes are more than a month from harvest, the temperature, should be 40°-50°F (4.4°-10°C), and closer to the lower end of the range is best for long-term storage. In summer we work hard to reduce the temperature to 50°F (10°C) for long-term storage, but in the winter we can reach 40°F (4.5°C). Constant temperatures or a steady decline is the goal, not dramatic fluctuations, as these can cause stress and physiological aging, which leads to sprouting. Hotter temperatures promote more rot, and age the potatoes faster, also leading to early sprouting.

Potatoes have a natural dormancy of 60-130 days (depending on the storage temperature). After that period, they will start to sprout.

I will address long-term storage and preventing sprouting in Part 5 next month.

Resources

The Potato Association of America, Commercial Potato Production in North America 2010.

2016 Organic Production and IPM Guide for Potatoes from Cornell has a big focus on dealing with diseases and pests.

Don’t let your potatoes sprout in storage (more next month)
Photo Jesse Strassburg