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Diary of a Vegetable Gardener – White Mold

My potato blues

Everything was going so well in the garden and then disaster struck. I had placed a yellow marigold in between a row of potatoes to help draw aphids away from the potato plants, but I didn’t take it out of its original container. It was a forgotten plant in the midst of tending to an entire garden. When I finally remembered about it and took it out of its container, I was pleasantly surprised to find it still a healthy plant, despite the lack of attention. I was, however, horrified when I picked it up and discovered white mold in the potato field. I was devastated.

Nothing had prepared me for this. I am a researcher. I read a tremendous amount about growing potatoes before embarking on the journey. I read a lot about hilling with straw before deciding to use that as well. Never, did I encounter anything about white mold. I instantly googled “white mold in growing potatoes“. The results came quickly with studies from the University of Idaho Extension and Michigan State University Extension. There was a wealth of information on white mold and I couldn’t help but think, why wasn’t any of this in any of the articles and studies I had read originally? White mold is a huge problem for potato farmers.

Finding white mold answers

White mold on potato plants is called sclerotinia stem rot. It is an amazingly resilient mold that can exist in soil for years. I paused for a moment when I read that, and my jaw dropped. Years? The white mold is from a soil-borne fungus Sclerotinia sclerotiorum, that has a long life cycle. It goes dormant over winter and then in the spring when it warms and the top two layers of soil are moist for a period of time, it germinates. This is my first year growing potatoes in my garden that was completely barren land just a few months ago. How was this mold already present?

I continued my research feeling defeated. The potato plants look so healthy. The stems are strong with lush green color and beautiful purple flowers have bloomed. If you looked at them, you would think nothing was wrong at all. It was hard to accept that that was all a facade and soon the stems would hallow and wither. The flowers would fall to the ground and perpetuate the problem.

An epiphany

At 11:30pm, after a full evening of research, I had an epiphany. What if it wasn’t white mold on the potatoes? What if it was just white mold on the straw? I began a new wave of research. Photos of white mold on straw and questions on forums about white mold on straw instantly came up, and best of all, with answers. My breath caught and then my shoulders relaxed with relief. The photos looked like mine and the clear answer was that mold on straw was normal and part of the decomposition process. Could it really be this simple? Were my potatoes going to be OK? It was far too late and dark for me to venture down to the garden to check my theory so I had to wait until morning to confirm it.

Confirmation, the moment of truth

I woke up early and quickly made my way to the garden full of hope and anticipation. I opened the garden gate and took a long look around. Everything looked so beautiful in the morning light. Then I turned my attention to the matter at hand. I reached into the straw from one side of the potato hill and gently pulled it away. I was surprised how dry it was inside since the outside layer of straw was soaked from two days of rain. Hope grew as I moved the straw and reached the base of the plant. Nothing. A healthy green stem stood with glory. Nothing was wrong with it. Could this really be? I hilled the straw back around it and moved to the other side of the potato hill. I repeated the process slowly and found mold throughout the straw, but when I reached the potato stem all was well. Again, it was a healthy plant. The white mold was indeed only in the straw. A sense of relief flooded me and I looked up at the purple potato flowers with gratitude. They were healthy and everything was well.

A lesson learned

A great lesson was learned here: never lose hope. Gardening is an adventure with ups and downs. We can try our best to have a lush garden, but some things are indeed out of our hands. Knowledge and determination are the best assets we can have as gardeners. I had done so much research on growing potatoes but nothing had prepared me for the white mold. The discovery of the mold was devastating and I could have let that get the best of me, but because I didn’t give up, I learned a lot. White mold is simply part of the decomposition process of straw and how organic matter is returned to the soil. It’s a good thing, but it came with fear. With the absence of knowledge comes fear and that is why I constantly surround myself with knowledgeable friends, colleagues, books and more. It sounds a bit cheesy, but I’ll leave you with this thought, the more you know, the more you grow.

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