Grow your own potatoes
Potatoes are an excellent choice for the home garden. They emerge quickly and grow rapidly. Potatoes yield well under most soil and growing conditions and can be stored for long periods without canning, drying, or freezing.
Few gardening activities are as rewarding as unearthing a hill of tender, new potatoes for dinner. They can be mouth-watering when prepared by any method, alone or in combination with other foods.
Potatoes are not only delicious but also highly nutritious. They are rich in starch, but an average-sized baked potato contains only 90 to 100 calories—slightly more than an apple and equivalent to one-half cup of cottage cheese. Potato protein has a well-balanced complement of amino acids and is among the best to be found in vegetables. Tubers are a good source of trace minerals and several vitamins, including vitamin C.
While potatoes perform well in most situations when properly cared for, they are susceptible to a number of pests and disorders. Good yields and quality can be achieved in most situations by following the suggestions given here.
Selecting a Variety
Selecting the proper variety, or cultivar, is important since varieties differ in yield, cooking characteristics, time of maturity, skin and flesh color, and storage life. Varieties traditionally have been classed as
white,
red, or
russet, based on skin color and texture. Increased interest in new gourmet varieties has added purple, blue, orange, yellow, and other colors to the inventory.
Tubers of standard white and red varieties generally are round to oblong and relatively thin skinned compared to russets. Russet tubers tend to be oblong and relatively dark colored and thick-skinned at maturity. Because of their thick skins, russet varieties are less susceptible to injury during harvest than reds or whites. The thick russet skins generally also are resistant to common scab.
Gourmet varieties are available in many color combinations and tuber shapes. Home gardeners can enjoy varieties not available in grocery stores. Such varieties are grown more for special features such as color and taste than for high yield and good storage.
Consider the time span from planting to maturity when selecting a variety. Norland, for example, may mature in 80 to 90 days, compared with 120 days or more for Russet Burbank. Early-maturing varieties are a better choice for “new” potatoes, but late-maturing varieties store better because they resist sprouting and shriveling in storage.
Select a variety suited to the method of cooking you prefer.
While the leading United States variety, Russet Burbank, is excellent for frying and baking, it often is inferior to Kennebec or Red Pontiac for boiling. Some also consider baked Russet Burbank tubers too dry. Many home gardeners prefer to grow an all-purpose variety such as Kennebec, while others grow several varieties for specific uses.
The following varieties are satisfactory for Oregon home gardens. You may want to try more than one.
Early-Maturing Varieties
Norland, Dark Red Norland:
Red-skinned with white flesh. Produces low to medium yields of average-sized tubers. Tuber shape and appearance usually are excellent. The earliest variety currently grown in Oregon. Good for boiling and frying, fair for baking. Somewhat resistant to common scab but less so than russet-skinned varieties. Dark Red Norland, a selection from the original variety, produces darker, more colorful skins than the standard Norland, which is declining in popularity.
Norgold Russet:
Yields slightly more than Norland but also matures slightly later. Susceptible to blackleg and hollow-heart of tubers. Once the leading early-maturing variety in Oregon, Norgold has been replaced by Russet Norkotah at the commercial level. Fair to good for baking, french frying, and boiling. Seed may be in short supply and unavailable at most garden centers.
Russet Norkotah:
An outstanding early russet. Oblong tubers are extremely attractive with excellent medium russet skins. Tuber physiological disorders such as knobs and hollow centers are very rare even under extremely dry conditions. Susceptible to early dying caused by verticillium wilt but highly resistant to common scab. Fair to good for baking, frying, and boiling.
White Rose:
White. Tubers generally are long, thin-skinned, and deep-eyed. Good yields. Will not bake well early but satisfactory for most other uses. Flavor and texture generally not as good as Kennebec. Slightly later maturing than Norgold.
Mid-Season Varieties
Kennebec:
White. An excellent all-purpose potato. High yields of large tubers. Susceptible to scab and greening when not hilled properly. Boils, bakes, and fries satisfactorily. Excellent for french frying.
Red LaSoda:
Yields more than Norland. Tubers have bright red skins but may be slightly rough in shape with deep eyes. Widely grown in home gardens. Satisfactory to good for most home uses. Susceptible to common scab.
Red Pontiac:
Mid-season to late. Extremely high yields of large, deep-eyed potatoes. Good cooking quality for most uses. A good red storage potato. Generally too late for early “new” potatoes.
Late-Maturing Varieties
Russet Burbank:
Also known as “Netted Gem,” the “Idaho Baker,” and “Russet.” Leading variety in Oregon and United States. Medium to high yields of large, long, and often knobby, misshapen tubers. Excellent for baking and french frying, fair for boiling, but tends to lose shape and fall apart because of high starch content. Stores extremely well.
Century Russet:
Smooth, large, and oblong tubers. Good for baking, boiling, and microwaving. Moister than Russet Burbank when baked because of lower starch content. Satisfactory for frying. Resistant to several diseases. Extremely high yields of attractive tubers.
Ranger Russet:
Tubers similar to those of Russet Burbank but sometimes longer, less susceptible to knobs. Good for all table uses; better internal quality than Russet Burbank. Does not store as well as Russet Burbank.
Gourmet and Specialty Varieties
Many varieties of potatoes are grown for special features including skin and flesh color or unusual flavor. Such “gourmet” varieties often produce low yields compared with standard varieties and may not store as well.
Purple-skinned varieties:
All Blue, also called “Purple Marker,” and Blue Cristie are more commonly available to home gardeners than most others in this category. All Blue produces smooth, oblong, late-maturing tubers with dark purple skin and flesh. Blue Cristie tubers are purple skinned with some red-to-pink stripes, prominent eyes, and white flesh. The variety Brigus produces smooth, round, purple-skinned tubers with light yellow flesh.
Yellow-Skins and Flesh:
Popular varieties in this category include Yukon Gold, Yellow Finn, and Bintje. Yukon Gold tends to produce smoother tubers and matures earlier than the other two. Yellow Finn stores well.
Red Skin, Yellow Flesh:
Desiree is probably the best known and most readily available variety in this group. Others include Saginaw Gold and Iditared.
Soil and Fertility Requirements
Potatoes do best on fertile, well-drained loamy or sandy soils but can be grown on virtually any soil if high yields and smooth appearance are not essential. Soils with a high pH (alkaline) or extremely high organic matter cause severe scab problems in susceptible varieties, including most round whites and reds.
Tillage
Work the soil to a depth of 6 to 8 inches before planting. The seedbed does not have to be perfectly smooth as is required for small-seeded crops. Excessive tillage actually can cause the soil to seal over after heavy rains, leading to seed piece suffocation and death.
Fertility
Potato plants require 16 or 17 mineral elements (nitrogen, phosphorus, sulfur, calcium, magnesium, potassium, iron, manganese, molybdenum, copper, boron, zinc, chlorine, sodium, cobalt, vanadium, and silicon) for maximum yields and quality. However, most are needed only in trace amounts and are provided in sufficient quantities by most soils.
Most commercial fertilizers contain only three major elements— nitrogen, phosphorus, and potassium—and sometimes a fourth, sulfur. By law, the fertilizer analysis must be displayed on the container.
Fertilizers typically are identified by three prominent numbers separated by hyphens (10-20-20, 12-12-12, etc.). The first number always refers to nitrogen, the second to phosphorus, and the third to potassium. If a fourth number is present, it typically refers to sulfur.
The fertilizer analysis means the following:
- Nitrogen (N) content always is expressed as the percentage of actual nitrogen.
- Phosphorus (P) content is expressed as the percentage of P2 O5 . Multiply the number shown on the package by 0.44 to determine the actual P content.
- Potassium (K) is expressed as the percentage of K2O. Multiply the number shown on the package by 0.83 to get the actual K content.
Thus 10-12-12 fertilizer contains the following:
Figure 1 - The three numbers on fertilizer packages represent nitrogen, phosphorus, and potassium.
- 10 percent nitrogen
- 5.28 percent phosphorus (12 percent P2 O5 x 0.44 = 5.28 percent P)
- 9.96 percent potassium (12 percent K2 O x 0.83 = 9.96K)
Fertilizers normally are applied at or shortly before planting either by broadcast or band applications or a combination of the two. Many gardeners hand broadcast the entire amount and work it into the top 3 or 4 inches of soil by rototilling or raking.
A more effective but time consuming method is to place all or part of the fertilizer in a band 3 inches to the side and 1 inch below the seed pieces. A combination of broadcasting half and banding half of the fertilizer usually is more effective than either method alone.
Never place fertilizer on or directly above the seed pieces; the fertilizer salt will dehydrate and damage or kill the seed pieces and developing roots and shoots.
When the potato plants are about 6 inches tall, some gardeners band or “side-dress” additional fertilizer beside the rows. As a general rule, do not side-dress more than about half the amount that was used at planting. Side-dressed fertilizers always should be covered with soil or watered in shortly after application to prevent excessive loss of nitrogen to the air as ammonia.
Never use “weed and feed” fertilizers on vegetables. They contain herbicides that will kill many crop plants.
Fertilizer requirements for potatoes differ among Oregon geographical regions. Central and eastern Oregon soils, for example, normally require less phosphorus than western Oregon soils but may require more sulfur.
Fertilizer and lime rates should be based on soil tests for best results. A soil test is indispensable for precisely determining lime and fertilizer needs. Soil tests are highly recommended for the first cropping season and at least every second or third year thereafter. Information on soil testing is available from county Extension offices.
While not ideal for every situation, the following fertilizer recommendations are satisfactory for most Oregon home gardens.
Complete 1:1:1 (approximately equal percentages of N, P2O5, and K2O) or 1:2:2 fertilizers generally are preferred unless soil test reports suggest otherwise. Materials such as 10-10-10, 15-15-15, and 10-20-20 satisfy these requirements. They are widely available from most fertilizer dealers and gardening centers.
Apply 10-10-10 at the rate of about 7 pounds per 100 feet of row or 23 pounds per 1,000 square feet. Higher or lower analysis fertilizers should be applied at adjusted rates to supply about the same level of nitrogen.
For example, 15-15-15 applied at the rates of about 4.5 pounds per 100 feet of row or 15 pounds per 1,000 square feet would supply approximately the same level of nutrients as 10-10-10 applied at the higher rates. Any complete fertilizer similar to the above, applied at appropriate rates, will perform satisfactorily (Table 1).
Table 1: Fertilizer application rates
Fertilizer | per 100-ft row | per 1000 sq ft |
---|
10-10-10 | 7 lb | 23 lb |
---|
15-15-15 | 4.5 lb | 15 lb |
---|
20-20-20 | 3.5 lb | 12 lb |
---|
Nitrogen usually requires more management than phosphorus and potassium because it is easily leached below the rooting zone by over-watering or heavy rains. Do not apply more water than the soil can hold in the top 15 inches. Prolonged heavy rains prior to late July may call for additional nitrogen applications.
Some western and north central Oregon soils are low in sulfur and may require up to 1 pound per 1,000 square feet each year. Magnesium also may be low in some instances. Soil tests are particularly useful in detecting shortages of these elements. Recommended materials and rates will be recorded on the soil test report.
Soil Amendments
Soil amendments, cover crops, manures, and composted organic materials are excellent for increasing organic matter and long-term fertility of the soil. Such materials also tend to improve soil structure.
However, high levels of undecayed organic matter can promote scab on most white- and red-skinned potato varieties. Therefore, the use of uncomposted manure except in the fall is discouraged. If you wish to use sludge or recycled organic matter in or around your garden, you should know the nutrient (NPK, etc.) content of the material. You also should know possible health risks.
Manures tend to be overrated as fertilizer materials but highly underrated as soil builders. A ton of fresh cow manure, for example, contains only about 11 pounds of nitrogen, 3 pounds of phosphoric acid, and 10 pounds of potash. Concentrations of N, P, and K in dried manures may be three to four times higher than in fresh manures.
Poultry and sheep manures tend to be about twice as high in nitrogen and many times higher in phosphoric acid than cattle manures. Potash levels are about the same for all species. Unless fresh manures are applied in excess of about 5 tons per acre, recommended fertilizer levels should not be altered.
A good legume cover crop plowed under just before planting can reduce fertilizer needs by up to 20 percent. Remember, though, that undecomposed organic matter such as fresh manure or cover crop debris can cause severe scab infection in susceptible varieties.
While scab does not affect eating quality or storability, the unsightly skin lesions definitely detract from tuber appearance and may severely reduce market value. If scab is a problem, use resistant russet-skinned varieties.
Heavy liming is not recommended for potatoes in most cases since it increases the soil pH, which causes scabby tubers in most round white and red varieties. The pH should be held between 5.2 and 5.8, slightly acid, if scab has been a problem. Otherwise it should be around 6.5, since other vegetables do best at pH 6.5 to 6.8. Russet-skinned potato varieties, especially Russet Burbank, are highly resistant to the scab organism.