by Catherine Haug
Post updated 5/9/09 to add sections on Hilling, Harvesting, and Storage.
Things are starting to happen on the site of St. Patrick’s Community Garden (on the grounds of the Episcopal Church in Ferndale). In the next week or so, the initial planting area will be tilled and planted with deer-deterrent potatoes, pumpkins and some type of cover crop, to ready the area for the next years’ plots.
Watch this site for notification of the potato planting date. In the meantime, here’s some information about planting and growing potatoes, from Mother Earth new, Garden Gate Magazine, and Food Gardening Guide websites.
- It’s always recommended to test your soil for pH. Potatoes prefer an acidic soil in a range of 4.8 – 6.0. (4) The Montana Gardener’s Companion, by Bob Gough and Cheryl Moore-Gough, suggests:
“Agriculturalists recommend a soil pH of about 5.5 for potatoes because at that pH, the microorganism that causes potato scab becomes inactive and infection rates are low. … Potatoes grown on alkaline soils have more problems with potato scab infections than spuds grown in acidic soils.”
- Potatoes will mature in 90 – 120 days, and are heavy feeders.
While potatoes are easy to grow, they do prefer cooler weather, so timing is everything. Potatoes do not do well when temperatures climb into the 90s, especially above 95 degrees F. So you want them to be past the early bulking stage by the time hot summer days have arrived. (1)
Readying your Seed Potatoes
1. When you receive your seed potatoes, store them in cool storage (such as a root cellar) or your refrigerator, until ready to plant.
2. Planting should be about 2 weeks prior to the last anticipated freeze date of 28 degrees F or lower, since it takes 2 – 3 weeks for the shoots to emerge from the ground. For our area, the last frost date is May 15, so your potatoes should have been planted around May 1. Don’t worry that we’re already past that date; just get them in as soon as you can!
3. About a week before your planting date, remove the potatoes from cool storage, and place in a bright warm window, to ” help break the spuds’ dormancy and assure they will grow quickly when you put them into the still-cool spring soil.”
Potatoes do not do well when temperatures climb into the 90s, especially above 95 degrees F. (1)
Preparing the Seed Potatoes for Planting
See Garden Gate Magazine: Potato Planting (3) for good photos and illustrations.
4. Cut potato into several 1-inch chunks; include an “eye” on each chunk.
- Don’t cut the pieces too big (smaller chunks encourage the plant to get busy putting down good, strong roots, rather than living off the stored foods in the seed piece.
- Don’t try to get a lot of eyes on a single piece. Each eye produces several stems; too many stems will compete with each other and make a shaggy mess.
5. Let the pieces chit (air-dry) for 24 hours to toughen the outer layer of the potato to resist disease. Adding a light dusting of sulfur powder or Bordeaux mixture will help keep fungi from attacking them: shake pieces in a bag with a small mount of the powder, until evenly coated. (3)
Planting: Creating Mounds with Mulch
NOTE: For the St. Patrick’s potato patch, they will be tilling the existing hay field into the soil, for row gardening this first year. See Row-Gardens: Hilling with Garden Soil, below, for details.
Mounding with mulch works well for raised beds and other container gardening, but can also be applied to row gardens:
6. Work a trowel full of compost into a square foot of soil in a sunny, well-drained area of the garden. The soil should be loose enough for the potato to send down roots easily.
Take a piece of seed potato and press it firmly into contact with the soil. Be sure the “eye” faces up. (3)
Plant under at least 6″ of mulch, and 8 – 12″ apart. Allow 12 – 36″ between rows. (4)
7. Mound up with a 6″ deep mound of mulch over the potato. Then water gently to thoroughly wet the mulch; this will help it hold together. Keep the mound evenly moist.
8. When vines start to peek through the mound, begin feeding them with a “half-strength follar spray. Use fish-emulsion or seaweed extract once a week until the flowers open, then stop feeding.
9. Mound additional mulch around the stems each time they’ve grown about 6 more inches.
10. Potatoes (tubers) grow at the ends of stolons that the plant puts out wherever the stems are covered with mulch, so in time, your plant will have tubers in several sizes within the mound.
11. While less watering is needed when you use a good mulch (as opposed to soil for the mounds), they still need water during the 6 – 10 weeks after planting, when they start to develop their tubers. Water deeply, thoroughly, applying enough to moisten the soil 8 – 10 inches below ground. An uneven water supply can cause knobs or growth cracks in the tubers.
12. Your potatoes will all be within the mound, not beneath the general soil level, which makes it easier to harvest them a few at a time, without disturbing the rest of the plant. (3) See Harvesting section, below, for more detail.
Stout Method (Deep Mulching)
This method is named for renowned organic gardener, Ruth Stout, and requires good rich soil. “Potatoes are heavy feeders and they will respond dramatically to good fertility and tilth. Your yield will suffer to the extent that the soil you plant in lacks proper fertility and water”(1).
“Over the years, Stout’s deep mulching technique will help you build wonderful soil fertility plus conserve water. In the meantime, working some organic fertilizer [such as fish meal] into the soil while you are building the organic matter and fertility will pay big dividends with any method of growing potatoes, including Ruth’s.” (1)
What to use for mulch?
Stout recommends “hay, straw, leaves, pine needles, sawdust, weeds, garbage — any vegetable matter that rots.”(2) Recent research suggests alfalfa hay is the best, but use what you have, or what you can get.
How much mulch?
Dick Clemence, Ruth’s A-Number-One adviser, says, “I should think of 25 50-pound bales as about the minimum for 50 feet by 50 feet [2500 square feet], or about a half-ton of loose hay. That should give a fair starting cover, but an equal quantity in reserve would be desirable.” (2)
Planting in mulch
This is done the same way you plant in soil: pull some mulch aside and add your potato starts with the eye up, then cover them with the mulch. (2)
Cautions for deep mulching of potatoes
- “Be sure the mulch is not so dense and packed that the developing potato plants can’t find their way to sunlight.” (2)
- “If you have big problems with slugs or mice the deep mulch method can add to your troubles.” (2)
Row Gardens: Hilling with Garden Soil
This information is from Mother Earth News: All About Growing Potatoes, December 2008/January 2009 issue (5), and Food Gardening Guide: Caring for Potatoes, from the National Gardening Association (6).
1. Prepare seed potatoes as above (steps 1 – 5).
6. Prepare beds: [After tilling], loosen soil to at least 10 inches deep. Thoroughly mix in a layer of compost, along with a half-ration of high-nitrogen organic fertilizer (such as alfalfa meal), following label directions. No NOT use manure, as it is correlated with an increase in rough patches on spud skins.
7. Sow the seeds: Plant potato pieces 12 inches apart in 4-inch deep furrows, with eyes up. Cover the seed pieces with 2 inches of your enriched soil. Fill in the furrows with remaining soil after the first sprouts emerge; this is called “hilling.”
8. Side dress: The idea is to use half of your fertilizer when you prepare the beds, and the remaining half is added as a side dressing after the plants are 12″ tall, just before hilling up soil around stems.
9. Hilling: Hilling loosely with soil (or mulch, see above), encourages the tubers to grow into the mound or hill, from which they are easily harvested. It also protects the tubers from sunburn, and prevents weeds. It is best to use straw of weathered leaves for mulch. In slug-prone seasons, hill up loose soil over the bases of the plants instead of mulching.
The first hilling is done about a week after the first sprouts emerge, and a second hilling 3 – 4 weeks later. Watch this 1 minute video on “How to Hill Potatoes” on You Tube, from ExpertVillage.
10. Watering: Especially during the 6 – 10 weeks after planting, when they start to develop their tubers, potatoes need a steady supply of water. Uneven water supply can cause knobs or growth cracks in the tubers.
Water deeply, thoroughly, applying enough to moisten the soil 8 – 10 inches below ground.
You can harvest some new potatoes throughout their growing season, for eating right away, or allow them to mature before harvesting.
After harvesting potatoes in the early stages of summer, plant the vacated space with beans or squash, or with a cover crop of buckwheat, to replenish the nitrogen.
- New Potatoes (creamers and steamers) should be ready right after the flowers bloom. Just move the mulch gently out of the way and pop the new potatoes off the ends of the stolons with your finger. Take no more than 20% at a time, to avoid stressing the plant. Continue watering throughout the season, to keep them producing new potatoes. Stop all watering 2 weeks before final harvest; when leaves and stems have turned almost completely yellow, and are withering, the tubers are ready for harvest. (3)
- Mature, larger potatoes: stop watering after the flowers bloom. This causes the plant to start concentrating on developing the tubers. Then in the fall, when the plant starts to die back, move the mulch away and harvest the full-grown potatoes. (3)
[Cat’s note: I plan to plant red potatoes (Red Norlands) for harvesting new potatoes all summer long, and winter-hardy yellow-finn potatoes (Bintje) that I’ll allow to mature before harvesting and storing in my root cellar.]
Storing Harvested Potatoes
From the Food Gardening Guide: Caring for Potatoes (National Gardening Association)
1. Prepare for Storage: Gently knock off dirt (do not wash), and allow tubers to dry indoors, covered with dry towels, for a day or two. Protect from sunlight at all times, to prevent greening, that may result in bitterness (not to mention that the green substance is toxic).
2. Storage: Select the the less than perfect ones first, for eating; the most perfect ones are stored for next year’s seeds.
Wrap (as with newspaper – no colored ink) or bury in straw or sawdust, to protect them from light in storage. Store in a cool, 50 – 60-degree place. But remember that they won’t store forever (4 – 6 months). For longer storage, potato slices can be blanched (dipped into boiling water for a few seconds) and dried.
About 6 pounds of seed potatoes are needed to plant 50 feet of row — yield will vary from 75 to 125 pounds.
- Mother Earth News: www.motherearthnews.com/Real-Food/2007-04-01/When-and-How-to-Plant-Potatoes.aspx
- Mother Earth News: www.motherearthnews.com/Organic-Gardening/2004-02-01/Ruth-Stouts-System.aspx
- Garden Gate magazine:www.gardengatemagazine.com/extras/52potatoplanting.php
- Maryland Master Gardener Handbook
- Mother Earth News: http://www.motherearthnews.com/Organic-Gardening/Growing-Potatoes.aspx
- Food Gardening Guide: www.garden.org/foodguide/browse/veggie/potatoes_care/571
- The Montana Gardener’s Companion, by Bob Gough and Cheryl Moore-Gough