Permaculturing in Portugal

One family's attempts to live in a more planet-friendly way

Blighted potatoes

It’s been strange and untypical weather this Spring. A March as warm as June followed a very dry winter. In May, we had more thunderstorms than I think I’ve encountered in the rest of my lifetime, and periodic rain has continued into June. Wonderful weather for bringing the garden on. Wonderful weather for bringing on the various fungal diseases that thrive in warm, damp, humid conditions …

Potato canopy in potato bin

We’ve watched others in the valley and around spraying frantically and it doesn’t seem to have made any difference. Their crops are infected just the same. And inevitably, after more Smith and Beaumont periods in a month than you could shake a stick at, not to mention a downpour that gave the lush canopy a centre parting, I finally discovered potato blight (Phytophthora infestans).

The only thing to do in this instance was to cut the haulms before the blight had a chance to find its way into the tubers, even though there was no sign of imminent flowering.

After doing so, I dug down into a corner of the potato bin to see what we’d managed to grow from one plant. It was quite some depth before I encountered the first tuber. I had to dig down to the level of the lowest 2 planks. Good news from the point of view of the blight reaching the tubers. Bad news from the angle of proving the theory behind the vertical cultivation of potatoes.

Potato harvest from potato bin

This is what I harvested from this one plant. The potatoes are good, but there are few signs of any inclination to produce offshoots any higher up the stems than the first 20cm or so. If this is typical of the rest of the crop, then there are some questions to be answered. Is the lack of tuber-producing offshoots down to the premature harvest? The variety we grew? The environmental conditions which brought the potatoes on so fast? Other factors which I haven’t considered? Any combination of the above?

Reading up on potato blight, I was immediately struck by the fact that blight is not a problem affecting wild varieties of potato. It struck me because I’d made the same observation concerning the grapes on the quinta. All the cultivated vines are showing signs of black rot (Guignardia bidwellii), another fungal disease that thrives in warm humid conditions, but in cases where the vines have reverted to a wilder state in uncontrolled growth from the roots, there is no sign of disease and the growing fruit is abundant and healthy.

Black rot, Guignardia bidwellii, on grape leaf

Perhaps this is the lesson here? Rather than fight the processes of natural selection, we should simply adapt our tastes to the healthier, wilder varieties?

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  1. Bill McWatters September 13, 2011

    What do you mean by growing grapes wild. I prunedmy quinta this year and didnt note any signifigant growth from the roots

  2. Quinta do Vale September 13, 2011

    Maybe it depends on the variety. I don’t know a whole lot about grapes. But there are a lot of vines on this quinta which had this growth when I took it on. Many hadn’t been pruned in a long while and the energy of the vine was all in these offshoots cascading over terrace walls while the main part of the vine was weak and ailing. The leaves are a different shape and appearance from those sprouting from the main stem, and neither these nor the fruit growing on these stems appeared vulnerable to the rot.

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