Two reasons for a low spud harvest

Now understand that I haven’t harvested any of these yet, but I can tell by looking at the plants that I will probably end up having to buy potatoes this winter. And there are two reasons why I think it’ll be a bad year for my homegrown spuds.

First, this spring I amended the soil in most of the raised beds with compost. And that’s great, but some of it was pretty rich in green or nitrogen material. And as you can see by the plants in the photo, I probably added too much of this compost.

See how tall the leaves are? They’re REALLY tall for potato plants.

Now I understand: We have the height of the raised beds which makes the plants look taller, but what’s really happening here?

The abundance of nitrogen, which is fabulous for heavy feeding plants like broccoli, tomatoes, celery, and peppers. But for root crops like potatoes, carrots, and turnips, too much nitrogen is not your friend. Carrots, for example, will develop forked roots. Which can be somewhat amusing. As for potatoes, you get too much top growth at the expense of tuber formation.

Now the good side is that these stems are fairly strong. The other day we experienced strong winds and heavy rain. But the stems remained upright. This would not be the case if I was using a high nitrogen chemical fertilizer, which creates weak stems and, how should I say, couch potato plants. Pardon the pun.

Second, and this has to do with the compost itself. One of the advantages to using compost is that it naturally neutralizes the soil. For example, when I planted my first raised bed some 35 years ago, the soil pH was very low, I think around 4.5. Great for blueberries, but not for lettuce!

This is mostly the result of ash deposited from volcanic eruptions on the Alaska peninsula. For those of you who are new to Kodiak, the island is located on the ring of fire. As a result, the soil is fairly sandy-like, and acidic.

But when I started adding compost to the soil, it gradually brought the pH into balance. Which is around 6.5 or 7.0 on the pH scale.

Now for most home garden crops such as lettuce, peas, kale, zucchini, cucumbers and tomatoes, a pH of 6.5 is satisfactory for the most part. But, for potatoes, a pH of 6.5 or 7.0 is too sweet.

It sets you up for harvesting potatoes that become dotted with scab. Scab, which looks like corky lesions on your potatoes, is caused by a bacteria that occurs naturally in most soils.

That said, let’s bust a myth here and now: Scab is not caused by varieties of potatoes. It’s IN the soil, but this doesn’t mean that all potatoes end up with scab, right?

Just like us, the bacterium Streptococcus pneumoniae is commonly found in the nose and throat. But it doesn’t mean we walk around with pneumonia all our lives. Only when the right conditions prevail will we succumb to it.

In soil, given the right conditions such as higher pH or soil that’s too wet or chunky, this creates the conditions where scab bacteria flourishes.

The appearance of scab doesn’t mean your potatoes are inedible. But they won’t store well. And they don’t look very pretty on the dinner plate.

So, lesson learned? No doubt. I will be really surprised if I get a decent harvest from these plants with such tall foliage, but I will keep you posted as to what happens.

So there you have it, two reasons why your potato harvest might not meet your expectations.

Meanwhile, check out my new YouTube channel, The Gardener’s Coach. Just go to YouTube and type in “The Gardener’s Coach” and remember, if you have a gardening question, get it off your chest: mygarden@alaska.net.