And then, a familiar thing started happening. The heat hit and my plants started going down one by one in a blaze of glory. Does this sound familiar? Yup. It's the same thing I was whining about last summer. And just like last summer, at first, I just thought I had not planned properly for shade. But then I started seeing some posts on the Tucson Backyard Gardening Facebook group that started making me look closer at my plants.
The tomatoes and green beans were dying from the bottom up. The leaves were getting yellow. And here's what really got me thinking: they were developing brown spots along the leaves. That's not the look of a plant dying from heat. That's the look of a plant that's diseased.
I can't know for sure what my tomato plants and green bean plants had, but all signs pointed to fusarium wilt. (The only way to really know would be a lab test.) Looking back, it seems likely that a lot of my plants had fusarium wilt last summer too. So it seems pretty likely that the disease is living in my soil.
That's the bad news. The good news is that our climate is perfect for treating the problem without chemicals. To get rid of fusarium wilt (and many other soilborne pests), you can cook 'em out using a method called solarization. (Doesn't "solarization" sound like it's custom-made for Arizona?) Solarization is a process where you lay plastic over the soil to concentrate the sun's heat to raise the soil's temperature. In cooler climates, people use the technique to start growing plants earlier in the season, when the weather is cold. In hotter climates, we can use the technique to bake nasty stuff like fusarium wilt out of the soil without using chemicals. Cool.
The process is pretty simple: Till the soil to loosen it up, smooth it out so the plastic can lay over it very evenly, soak the dirt really well, lay the plastic over it very tightly, and let the soil bake for 4-6 weeks. (Times will vary depending on the weather.) To get more details, I recommend this excellent article from UC Davis, a renowned agricultural school: Soil Solarization for Gardens & Landscapes.
Lucky for me, I don't have to solarize my whole garden (just most of it), so I do have a few zucchini and melon plants to hold me over while everything else bakes. Good thing, or I might go crazy with nothing to grow for a month and a half! I'll let you know how things go. In the meantime, happy gardening and stay cool.