Sunday, February 16, 2014

Planting and Harvesting Potatoes

It's time to get our potatoes in the ground.   They should survive just fine, even if we have another cold snap.  If green shoots peek above the ground and a freeze is predicted, just cover them with some straw or hay.

The soil should be light, fertile, and somewhat acidic.  Potatoes like soil between 5.0 and 5.5.  Do not use lime (high pH) soil for potatoes.  High pH soils encourage potato scab disease, which makes the potatoes unsightly, but usually not unusable.  See below for more on soil pH.

Cut the seed potatoes into planting pieces containing one or more eyes.  Allow them to dry and callus over for several days before planting to discourage rotting.  Dig a trench about 6 inches deep. Place potato pieces at the bottom of the trench with eyes up about 18" apart.  Cover with about 3 inches of soil.  When the plants are 5 to 6 inches above the soil, add soil to fill in the trench and as the plants grow, continue to mound up around them.  This will encourage the plants to grow potatoes in layers up the stem, and increase your yield.  Add a 10 to 12 inch layer of pine straw to insulate the soil, keep the potatoes cool and moist, and to keep any sunlight from turning exposed potatoes green and inedible.

For best yields and better storage, potatoes should not be dug until two weeks after the vines are dead.  For earlier harvest, cut the vines and allow the potatoes to remain in the ground for several weeks.  This allows the skins to toughen and reduces skin peeling and bruising, and increases storage time.   If harvesting when temperatures are above 80 degrees, potatoes should be picked up immediately and stored in a cool dark place.  Of course, digging carefully around under the growing plants and stealing a few small "new" potatoes to enjoy in the Spring is one of the pleasures of gardening.  You should be able to find small potatoes just right to eat when the plants start blooming.

'If your soil test shows a higher pH, consider working some sulfur into the soil such as granular sulfur sold as ammonium sulfate or magnesium sulfate. 

Adding organic matter to the soil such as well-decomposed compost, leaves, etc., will help to balance the pH.  Mulching with pine straw will lower pH over time, if used consistently.   Lowering pH is one of the hardest adjustments to make in soil composition

The pH of the soil is important because the proper pH is necessary for plants to access the minerals in the soil.  Your garden can have all the necessary nutrients, but the plants cannot utilize them unless the pH is in the right range.

Rotate your potato planting from year to year to discourage accumulation of plant diseases in the soil.  Don't plant potatoes where you had tomatoes the previous season as they are in the same plant family. 

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