Plant of the Month: Potato

Potatoes and Maine have a long tradition together. Potatoes have always been a popular crop in home gardens, especially since they can be stored for use during the long Maine winter. Potatoes can be grown in all parts of Maine in home gardens, but they need more attention and care than most vegetables. If you do a good job controlling insects and diseases, you’ll improve potato yields, and also protect Maine’s commercial potato industry.

Potatoes do best in fertile, well-drained soils. While they do well across a wide range of pH, potatoes prefer slightly acidic soils; a soil pH of 5.3 to 6.0 is typical for potato production. If your soil has a higher pH, chose a scab-resistant variety, such as “Russet Burbank.”

Potatoes are traditionally grown from seed pieces. These are not true “seed,” but pieces of a potato tuber. Do not use potatoes purchased at the grocery store for seed pieces. They are probably treated to not sprout. Buy certified seed from a reputable seed seller. Buying certified seed pieces assures varietal purity and a low level of diseases. 

A soil test will tell you whether to use fertilizer and, if so, how much. If you don’t have a current soil test, you might apply a balanced fertilizer (for instance, 10-10-10) at a rate of about 30 pounds per 1,000 square feet, or about one pound per every 10 feet of row. Manure is not recommended on potatoes. It tends to encourage scab development. Save the composted manure for other garden crops.

As soon as the soil warms up to 50 degrees F, potato seed can be planted. Seed spacing ranges from eight to 16 inches within the row and 30 to 36 inches between rows.  Close spacing in the row (6” to 8”) aids in reducing tuber size and increases the number of tubers set. Using close spacing can reduce hollow heart and growth cracks.  If you are planting larger cultivars such as Russet Burbank spacings of 12” to 16” will produce large bakers.

Make a furrow four to six inches deep, and, after fertilization, place seed in the furrow and cover with two inches of soil. Once the plants are about six inches tall, they should be hilled by mounding soil on top of the row. Up to three hillings may be needed to build a potato hill, depending on conditions. Tilling will help control weeds between the potato rows. But if you’re using a garden tiller, be careful you don’t damage potato roots and stolons.

Late blight and early blight are two potato diseases that are common in home gardens. Of the two, late blight is the real threat. Late blight from an infected garden can spread spores and affect commercial potato production miles away. You may wish to consider potato varieties with some late blight resistance, such as “Kennebec.”  Colorado potato beetles and aphids are common potato insect pests. There are insecticide/fungicide combination products that will control both these insects and foliar diseases. There are insecticides and

fungicides that are approved for organic production.  Contact the Extension Office for information on insect and disease pest control.

Potatoes are traditionally harvested at the end of the growing season but some gardeners can’t resist harvesting a few small potatoes during the growing season to eat with their other fresh vegetables.  Here is a chart of a few popular cultivars that home gardeners might enjoy.