Spacing between plants is a matter of how deep you are planting the seed potatoes. If the trench is 6 to 8 inches deep, the potatoes should be placed in the trench at 12- to 18-inch intervals. If the trench is shallower because of environmental constraints or personal preference, then the spacing needs to be wider to allow the roots more room to forage for moisture and nutrients. The shallower the trench, the farther apart the seeds should be placed--up to several feet apart.
Each trench will eventually be filled in and more soil added throughout the growing cycle, creating a "hilled" effect. For large-volume crops, where equipment is being used to do this work, the rows need to be 5 feet apart. For the home gardener, 2 to 3 feet between rows is sufficient. This allows ample working room between the rows for the gardener to work and enough room below the soil for the roots and developing potatoes.
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