Question
Mike

I need some help, for the last 2 years I grew kennebec potatoes.Both years the potatoes were huge grapefruit size or a little bigger. I planted them 12" apart. Which this was ok with the average was 4-6 per hill. Now the real problem, both years have very odd shapes almost like 2-4 of them grew together and were joined together almost looking like mickey mouses head with the two big ears. and some on the bigger portion it seemed like it split open during growing and healed over and continued to grow.Help Why is this and what can I do to grow semi perfect size and shape potatoes like you buy from the store?

Answer
Matt, based on your description, my guess would either be the soil composition or the harvesting time. Potatoes should be grown in loamy soil that has been highly supplemented with organic matter such as shredded leaves, compost, aged manure, and peat moss.  It also must have good drainage to prevent the potatoes from rotting. Heavy soil, such as clay, will cause them to distort and split.

Potatoes also prefer slightly acidic soil.  You can achieve this by adding some gypsum or sulfur in moderation.  You can these products at any reputable garden center.  If you're not sure what the pH level (measurement of acidity or alkalinity) is, you can test it with a simple kit that is also available at most garden centers.  The soil should measure a reading of 6.0 - 6.5 for potatoes.

If you don't have compost and the other supplements I described readily available, you can order organic soil by the yard from a local landscaping yard.  Just give them the dimensions of your planting bed(s), and they will advise you on how much you need.

Although you can plant potato seeds whole, I recommend cutting them into pieces, making sure that each piece has 2-3 eyes.  If your climate is wet, you must first dust the seeds with sulfur to prevent them from rotting.

Potatoes are a cool season crop and should, therefore, be planted 2-3 weeks before your last expected frost.  Just be sure to plant before the temperatures stay consistently above 80F. Never try growing potatoes from the grocery store. They are usually sprayed to prevent sprouting.  Instead, always purchase certified, disease-free seed potatoes from a garden center or nursery.

Space the seeds at least 6" apart and cover them with 5" of soil. As the vines begin to grow, make sure you continually hill or mound them with soil or straw to keep the tubers completely covered.  Otherwise, the potatoes will turn green and potentially toxic.

Once the vines begin to flower, stop mounding the soil and start mulching heavily with straw to conserve moisture.  Water deeply at least twice per week.  Do not fertilize with a high nitrogen fertilizer.  This will result in lush top growth and very small tubers.  As I mentioned earlier, I recommend planting the seeds in well amended soil consisting of compost and/or aged manure.  This will virtually eliminate the need to fertilize at all.

Once the foliage begins to brown and wither, the tubers should be fully grown.  Dig them by hand to avoid puncturing them with a spade or pitchfork.  Since they will keep in the ground for several weeks after maturing, you should wait until the soil dries before harvesting.

I hope this information proves beneficial. Please write again if I can ever provide assistance.

Regards,

Mike