Gardening Basics: Potatoes

Getting Started With Potatoes
By: the Editors of National Gardening
Since most home gardeners start potatoes by cutting and planting last season's tubers, common sense says you should use the healthiest tubers possible.

Disease-free Spuds

How do you acquire disease-free potatoes for planting? Simple, go to a good garden store in the spring and buy certified potatoes for your "seed" or order your seed potatoes from a reliable mail-order source or on-line.

Certified seed potatoes are grown under carefully monitored conditions where state agricultural inspectors enforce high standards of disease and pest control, plant health and quality of harvested tubers. Most certified seed potatoes are grown in northern states where there are fewer disease-spreading insects than in the South. However, the cooler temperatures of the North favor the development of some diseases. Plants that do become infected at the breeding ground can be spotted and eliminated, leaving only the strong disease-free plants.

Gardeners who save some of their own crop to use for seed potatoes the next season are taking a chance. While the tubers may look fine and be perfectly okay for eating, certain virus diseases may be present. If these potatoes were planted, the disease would likely pass from the seed piece to the new plant.

Buying Market Potatoes as Starters

Potatoes from the market generally don't make good seed potatoes. They may have diseases and usually are treated with a growth-stopping chemical so that they won't sprout in the stores or in storage. Buying certified seed potatoes locally or through the mail is a better idea.

In many areas, garden stores buy certified seed potatoes in 100-pound bags and break them down into smaller packages for gardeners. How much should you buy? Eight to ten pounds of seed potatoes should plant a 100-foot-row and with that length of row, you could harvest three to four bushels of potatoes if you let them grow to maturity. If you harvest some when they're small for midsummer eating (around flowering time), the total yield will be less. If you get your seed potatoes and can't plant them right away, simply store them in your root cellar or a cool, dark, well-ventilated place.
Planting Potatoes
By: National Gardening editors

Growing Potato Towers

Ever think of growing a few potato plants in bushel baskets to make a potato tower? Well, you can -- it's easy and fun. You can be a potato grower in the smallest yard or just on the back porch or patio.
Line a bushel basket with plastic and punch a few holes in the bottom for drainage. Stir a few tablespoons of houseplant food or fertilizer into a bucket of moist soil. Put a 4- or 5-inch layer of soil in the basket. Position several seed pieces 6- to 8-inches apart on the earth, then cover them with 3 or 4 more inches of soil. Keep the basket in a warm, sunny place. As the plants grow, add more soil around the stems to give the tubers room to expand, and be sure to keep the soil well-watered.

Caring for Potatoes
Caring for potatoes requires proper watering, cultivating and hilling.
Cultivation
Stirring up the soil on the surface keeps it loose so that the plants' roots can get water and air. They have to drink and breathe just as we do. Whenever the soil becomes packed or crusty, raking the top inch of soil lightly can help.
If you hill your potatoes during the first four to eight weeks after planting, you shouldn't have any problems with weeds. Hilling buries weeds near the plants, and it usually takes care of most walkway weeds, too.
Once the hills are made, though, don't disturb them with a hoe or any other tool. If you want to remove some weeds, pull them by hand.
Hilling
There are several reasons why you must pull soil up around the stems of your potato plants, or "hill" them, once or twice during the season:
* The additional loose soil allows the developing tubers to expand easily.
* Hilling helps to keep the potatoes from poking through the soil and becoming "green" from the sun. ("Greening" gives them a bitter flavor.)
* Hilling buries and kills weeds around the plants before they become a serious problem.
* Rain collects in gardens with heavy soils, blocking the flow of air to the plant roots. However, a hilled row of potatoes sheds water. Hilling keeps the plants better drained and more productive because the earth doesn't pack around them.
* Pulling soil from between the rows up around the plants creates a natural irrigation ditch.
Hill the plants for the first time about a week after they poke through the soil. Do the job with a hoe or a tiller with a hilling attachment, and pull up as much soil as you can around the stems. If you cover some, or even all, of the leaves of the plants, don't worry about it. They'll push back through in a few days. In fact, if your early planted potatoes are up and there's a chance of a late frost, you can cover the plants entirely to protect them from injury. Potatoes can take a light frost; burying them is just added insurance.
Do the second hilling three or four weeks later, before the potato vines spill out into the walkways.
Proper Watering
Potatoes need a steady, season-long supply of water, but it's most important 6 to 10 weeks after planting, when the plants start to develop their tubers.
An uneven water supply can cause knobs or growth cracks in potatoes. If the plants don't get enough water, the tubers won't grow and their cells will start to mature. Then, when a sudden increase in water does occur, the potatoes start a second, new growth, causing the tubers to crack or develop into odd shapes.
Deep Watering is Best
Potatoes can take some periods of dry weather. However, if it's been very dry and the tubers are beginning to develop underground, water the plants. If you need to water, be sure you do a thorough job, applying enough to moisten the soil 8- to 10-inches below ground. Deep watering is the only way to go. Research shows that irrigated potatoes obtain 57 percent of their water from the top foot of soil, 24 percent from the second foot of soil and as much as 13 percent from the third foot of soil. Though the potato plant is mostly shallow-rooted, some roots do indeed go deep for water.
Photography by NationalGardening.com
Harvesting Potatoes
By: the Editors of National Gardening
After all your work of planting and caring for your potato plants, here's how to get the most from your harvest.

New Potatoes

The earliest or "new" potatoes of the season are a treat not to be missed. They're small, round, smooth and delicious. When you think you have early potatoes big enough to eat, reach into your early hills, feel for the best-sized spuds and ease them out. The plants keep right on growing and producing more.

During seasons when the soil has been quite moist (which makes hunting by hand tougher), dig up entire plants, harvest all the baby potatoes you can find and put the plants back in the earth. They'll survive this rude transplant and produce quite a few more potatoes. But working fast is important; freshly dug potatoes shouldn't stay in the sun very long.

The best tool for digging is a 5- or 6-pronged fork. Dig down under a hill, then lift up. The dirt falls between the prongs, and you're left with a forkful of potatoes. There's less bending this way, too.

Later Harvest

In the North, harvest the main storage crop in September, when the days are getting cool and frost isn't far off. That's when the plant tops are dying and sending the last of the vines' energy underground to the tubers.

If you'll be storing most of the late potatoes, wait for the best weather conditions possible before digging them up. Choose a warm, dry day after a period of little or no rain. Cloudy days are even better, since too much light turns newly dug potatoes green, changing their flavor.

After you dig a few hills, you'll discover that all the potatoes in a hill are at pretty much the same level. Once you figure out how deep to dig your fork, you won't injure as many potatoes. Of course, if you've got some beginners on the work crew, there'll be a few spiked spuds. Put them aside for the evening meal; they won't keep. A pointed shovel does a good job, too. You can dig deep enough next to a hill to raise the entire hill at one time.

Be gentle. Try not to rough up or bump the potatoes. Each bruise lowers the storage quality and appearance of the tuber.

After the Harvest

Leave the potatoes outdoors for an hour or so to dry. During that time most of the soil stuck on them should also drop off. There's no real need to brush the tubers, although some people use a very soft brush gently to take off clumps of dirt. Don't wash the potatoes; it's hard to get them really dry afterward.

Put the potatoes in the dark after they've dried in the open for a short time. Don't leave them in burlap bags or other containers where light can penetrate and start them greening.

If possible, storage potatoes should have a short drying or "curing" period of one to two weeks after the harvest. Curing allows any slight cuts or bruises on the potatoes to heal rapidly. Keep the tubers in a dark place with temperatures around 55o to 60oF with high humidity of up to 85 or 95 percent.

After a curing period, move the potatoes to a much cooler, dark place for winter storage. Experts recommend 35o to 40oF with moderate humidity and ventilation. If these standards are met in your basement or root cellar, you can expect mature potatoes to store for up to eight months. Higher temperatures will mean quicker sprouting and shriveling.

Because potatoes have to breathe in storage, a root cellar needs good air circulation The potatoes are still carrying on normal life processes, using oxygen to heal bruises and cracks and giving off carbon dioxide, heat and moisture. Good air circulation in the storage room helps this continuing process. A good way to store potatoes is in bins with slatted sides and bottoms; however, don't pile them higher than 6- to 8-inches tall.

Occasionally, potatoes turn "sweet" during storage. This happens because potatoes convert a certain amount of starch to sugar, which is used up in the "breathing" process. When the tubers are stored in cool root cellars, the breathing slows down and they don't use up all the sugar they produced. Occasionally, this extra sugar gives the potatoes a sweet taste if they've been taken directly from cool storage and cooked. However, this is rarely a problem. If your potatoes sweeten, just bring a week's supply out of storage at one time and keep them in a warmer spot. The extra sugar will revert to starch -- a process experts call "reconditioning".

A Note on Green Potatoes

When potatoes are exposed to light their skins start to turn green -- a sign that a toxic substance called solanine is developing. This occurs if potatoes aren't fully covered by soil while they're growing, if you leave them in the sun for too long after the harvest, or if they aren't stored in complete darkness. Potatoes you buy from the supermarket also turn green if they aren't stored in a dark place.

Because solanine is slightly toxic, it's possible to get sick if you have a large helping of greened potatoes. Peeling or cutting away green sections before cooking usually eliminates the problem, as most of the solanine is located in the spud's skin.