Thinking ahead to planting potatoes

No matter what kind of winter we have, gardeners are always anxious to have spring come. The list of questions gardening enthusiasts have seemingly has no end. I always get lots of questions about potatoes.

Already this year, I have been asked about the soil fertility for potatoes.

Many gardeners, including me, think rotating the crop and adding manure is good enough, until they get potato scab.  We strongly suggest you have your soil tested as a baseline before you plant.  You will have plenty of time this spring because potatoes shouldn’t be planted until the ground is warm.  You can pick up a soil test kit at one of our classes or come into the Extension Office in North Branch.

Gardeners usually ask potato questions when something is wrong with their crop.  Potatoes are started from seed tubers, not from true seed.  Obtain disease-free seed tubers from a certified grower or seed distributor.  I know of gardeners who use their own seed year after year, and that’s OK if they are satisfied with their crop and there is no evidence of disease in the plants.  Planting potatoes purchased at the grocery store is not recommended, as they may be sprayed with chemicals to keep tubers dormant.  Or they may be infected with diseases that can remain in the soil for a long time.

Potatoes grow best in well-drained soil with a pH of 6 to 6.5, but will tolerate soil with a pH as low as 5.  Before planting, incorporate well-rotted manure or compost, or 1.5 pounds of 5-10-10 fertilizer per 100 square feet.   I took some of this information from the University of Minnesota Extension, and they also recommended some side dressing when the tubers begin forming.

I cut out an article from a magazine that answered a question on potato scab, but I didn’t keep the name of the magazine.  However, the article made a lot of sense.  It stated a reason for scab could be that the pH is higher than 5.5.  Putting a couple of tablespoons of sulfur in a paper bag and dusting the cut up seed potatoes may lower the pH.  This will also help keep the newly planted eyes from rotting if the spring turns cold and wet.  Again, start with a soil test and if what you’re doing works for you, keep doing it.  I shouldn’t be planting potatoes if the ground is cold and wet, but if it is, I may try dusting the cuts with sulfur before planting.

Jerry Vitalis is a Master Gardener from Chisago County

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