I hate to ‘dig’ up bad memories, but, do you remember the wet summer we had last year? I know most of you would rather forget but there is a reason for the flashback. Last year was a terrible year for ‘potato blight’, or ‘late blight’. The blight, Phytophthora infestans is the very same fungus that caused the Great Irish Famine in the late 1840s.
Do you remember those dark blotches that appeared on the leaves and stems? In some cases, all the foliage turned black and died back right to the ground. The tubers had a brown decay starting at the skin and eventually caused the tuber to rot. Seemingly healthy potatoes later rotted in storage.
Blame it on the weather and P. infestans. The spores of this fungus over-winter in the soil. That is why it is so important to rotate your crops this new gardening season. Do not plant either potatoes or tomatoes in the same location as last year.
Potato Blight also overwinters in any tubers that were left in the ground. So get rid of those new ‘volunteers’ as soon as they pop up. It is important to remove all of the infected tubers from the soil. It is better to burn infected foliage rather than compost it. Sometimes the compost isn’t hot enough to kill the spores on the leaves.
To reduce the risk of infection, only plant certified seed that is free of late blight. Don’t overcrowd plants. Plant seed potatoes 40 cm (16”) apart in the row and have rows 90cm (three feet) apart. Avoid excessive vegetative growth resulting from over-fertilizing or overwatering. Irrigate early in the morning so foliage has a chance to dry out during the day.
Tomatoes are in the same family as potatoes so do not plant these in the same location as the infected potatoes. This year, we have a new variety of tomato that is tolerant to the late blight disease. ‘Lizzano’ is a patio cherry tomato with good flavor and lots of fruit.
I leave you with some good news about the lowly spud.
It has a bad rap for being high in carbohydrates and having a fairly high glycemic index (GI).
This year we have a variety with a low glycemic index (rating of 58). Nicola has an oval shape with rich yellow skin and yellow waxy flesh. Good for baking or roasting. Nicola is excellent for boiling and salads. I say, ‘Bring on the butter!’
Jean Atkinson is a horticulturist with Richbar Golf and Gardens.