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Potatoes

Potatoes
Solanum tuberosum


Potatoes are easy to grow and fun to harvest. Grow certified seed potatoes in soil high in organic material, water lightly, and avoid eating any that are green.  
Photo: pixabay

WHAT

  • Modified stem (tuber)
  • Cool season perennial grown as an annual
  • Native to the Andes region of South America

WHEN TO PLANT

  • Plant potatoes as early as February and as late as May.
  • Tuber production occurs underground until soil temperatures reach 80 degrees.

PLANTING

  • Plant only certified seed potatoes to avoid disease.
  • Cut large tubers into chunks about 1½ inches in size with at least two eyes. Spread the chunks on newspapers in a warm well-ventilated place to callus for a few days before planting. Small potatoes the size of an egg can be planted whole.
  • Plant 3 inches deep and 6 to 12 inches apart.
  • When the plant is 6 inches tall, cover with another 3 inches of soil. This is called hilling and can be done again after 6 more inches of plant growth. Hilling increases production and prevents greening.
  • Potatoes are easily grown in containers.

SOIL

  • Plant in loose, light, well-drained soil high in organic matter such as aged manure or compost.
  • Unlike most vegetables, potatoes prefer slightly acidic soil.  (pH 6.0 to 6.5).

WATER

  • Water lightly once or twice a week, just enough to keep the soil from cracking and to avoid rot.
  • Stop watering when the plant turns yellow and begins to die back.

FERTILIZER

  • If organic matter is inadequate, use fertilizer with more phosphorus and potassium than nitrogen.
  • Excess nitrogen promotes leaf growth at the expense of potatoes.

POLLINATION

  • Self-pollinating

HARVESTING

  • Potatoes mature in 90 to 120 days.
  • Harvest can be spread out over several weeks.
  • “New” (young) potatoes can be harvested soon after the plant starts flowering, but be careful when you peek to not damage the plants.
  • When 20% to 100% of leaves have yellowed, harvest potatoes by digging well back from the plant stem. Discard green potatoes as they contain a high level of toxic alkaloid solanine.
  • Alternatively, cut off the plants at ground level and leave the crop in the ground for another couple weeks without watering to harden off the skin.

STORAGE

  • Store potatoes in a cool, well-ventilated place. Exclude light to prevent greening.
  • Use within six weeks for best flavor and texture.

GOOD VARIETIES FOR MARIN

  • ‘Buffalo,’ ‘Bison,’ ‘Carola,’ ‘Carlotta,’ ‘White Rose,’ ‘Kennebec,’ ‘Chieftain,’ ‘Nargold,’ ‘Russet,’ ‘Red Lasoda,’ and ‘Yukon Gold’

HELPFUL TIPS

  • Plant only certified seed potatoes.
  • Practice 4-year crop rotation.
  • Avoid heavy, wet soil.

COMMON PROBLEMS

  • Scab, a fungus, may cause blemishes on the surface. Simply peel off.
  • Early and late blight, two fungal diseases, cause plants to collapse and make potatoes inedible. Use certified seed potatoes and avoid overhead watering.

PEST, DISEASE, AND MORE