This may be the last update on the kitchen garden and the heat wave. In my last post I talked about the amazing contribution of the weed mesh/membrane and the drip hoses that seem to be saving my garden. But I also noted that the tomatoes were not ripening, and I did not mention that quite a few of the flowers were falling off. With one solitary exception each, my two courgettes are only producing male flowers. The plants look healthy and the two round courgettes were lovely (although I let the first one get too bog because I thought I had planted a Rond de Nice not a Rond courgette). No idea what is causing the courgette issue, but I do know what is wrong with the tomatoes. Even with mesh and moist soil it is too HOT. And clearly mesh and water work for a while, but after a while they are not enough.
The back-to-back heat waves have killed a lot of people, so my garden woes are inconsequential, but my tomatoes are suffering some pretty some serious heat stress, that’s a given when temperatures are over 90ºF (32ºC) for more than a few days. When we got to day 10 with daytime temperatures between 95º F (35ºC) and 105ºF (40ºC) preceded by a 5 day break in the high 80s (30ºC) — which is when the Andine Cornue’s started to ripen — but that was preceded by 9 days between 95 and 103º in late June. After another short break at the end of last week, we are back in the low 90s again and today (July 20) we have an expected high of 96ºF. Tomatoes need to be below 85ºF (29ºC) to get back to health and turn their energy from survival to ripening. Last week I realized I needed to do something more.
Research Rabbit: How can I cool my tomatoes?
The folks at TomatoBible.com explain that “in unusually high temperatures, tomatoes fail to pollinate. Under prolonged heat stress, the flowers fall off, leaving you with far less fruit than your plant can produce. The plant will also put all its energy into survival, rather than producing fruit.” Sounds familiar.
The previous owner of our house, the one who provided the great soil for the kitchen garden, said he used to plant corn where I have it to provide shade for the tomatoes. I copied him and now I understand why he did that. My corn is not high enough (and I have too many tomatoes), but is shade the solution? Hmm. The website FarmStandApp.com offers some advice about that (including planting corn or pole beans on the southern side of the garden). One of the “7 Best Soil Cooling Techniques For Gardens” is mulch (which can include weed mesh – check), another is a drip watering system (check), and a third is to provide shade in the hottest part of the day. The kitchen garden is in shade until around 11 am but then the sun blazes on it for the next 11+ hours. The folks at FarmStand suggest using a PVC frame to suspend shade cloth 2-3 feet above the tomatoes, noting that ideally it will cut the sunlight intensity by 30-50%! Next year I plan to do just that. Updates to follow!
I’m happy I learned all this about tomato heat stress, but I wish I had some the research earlier. I knew they needed water and soil cover, but have never lived anywhere with weeks of 90º+ temperatures.
Shade cover I
I looked up shade covers online and found several, but no one could deliver in under two weeks. So, time to improvise. I tied garden twine between the tomato stakes (8′ rebar) to make a frame, and used clothes pins to secure the extra-long net curtains I bought from the states to use in the attic and elsewhere (currently my office, and the window and side door in the living room). And I could feel the temperature drop around the tomatoes!
The window nets did the trick, but (a) I didn’t have enough, and (b) the clothes pins weren’t holding very well. Time to head to Gaillac garden stores and see if they had in stock what the Internet does not. The folks at Gamm Vert thought this was an interesting idea but had never heard of shade cloth for vegetables. To be fair, they focus on flowers and pretty things more than food crops. They suggested hessian, which was not a bad idea, but that would be too heavy when wet — if it ever rains!
Shade Cover II
In desperation I thought I could use fine mesh nylon mostquito netting of the kind you can buy by the meter in Mr. Bricolage. So that was plan C if I really couldn’t track down shade netting.
I tried RAGT on the way home with little optimism, but just to check all of the boxes. And there, on the shelf by the weed mesh, were four packs of ombranet, 2m x 5m. Now the planted space of my garden I needed to shade is 4.5m x 4m this year, so not perfect. But close enough to celebrate. AND, there on the sign it said “soldes” — not only did they have them, but they were on sale! I bought 3 packets (actually, I bought 2 that day and then went back the next day for a third). And I picked up a few more garden poles so I was all set.
The next day was the one that should have had rain. It did not rain, but it was mercifully overcast so I could get to work. Next year I plan to make a frame from PVC pipes and secure the shade fabric so I can lower it when I need to do so and roll it up when not needed. I imagined two long frames on either side of the garden where I did not plant tomatoes this year, allowing me to rotate between the two spaces and plant tomatoes in the space between the following year. Walter got a look of concern and declared it “quite ambitious.” Yes. So more realistically, I will probably just rotate one side of the garden and then the other with a smaller tomato patch and more peppers, basil, chives, and maybe beans and peas on the other side. And corn at the bottom as this year. I can expand the planting area to 6m x 6m if I clear the rest of the weeds. So that’s the plan.
Meanwhile, I have a shade net and while the temperature is currently hovering around 90ºF (32ºC) in the shade, and around 27ºC under the net. That’s all I need. Tomorrow the predicted temperature is back to 96º with mid-90s for the rest of the week, so this is the test.
I can say this: after three days of shade (one with curtains and two with real shade net) I harvested another dozen red tomatoes and more are ripening. We ate some still warm, with just a little salt. I took some to Andrée along with a few of the roses I have been coaxing through the heat. Four of the five varieties now seem to be ripening (Carmello, Andine Cornue, and Saint Pierre, and the small yellow pears), and all are really tasty although Saint Pierre has the edge out of the red ones and the yellow pears are as sweet as always). I feel cautiously optimistic, but even if this fails to ripen all of the fruit, I have learned a lot and next year the shade goes up as soon as the temperature does!
