growing sun-loving plants in the heat of the summer!

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rosbeal
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growing sun-loving plants in the heat of the summer!

Post by rosbeal »

We need help with greenhouse issues:
a) We grow our tomatoes, cukes, melons and eggplants directly into beds in our greenhouse which receives daylight from the morning until 6pm in the evening. Ideal or not??? this past summer was extremely hot. All of our plants struggled even with multiply waterings, the windows & doors open and fans running. Earlier in the spring when everything was still shut because it was still very cool outside, but with the sunshine, the greenhouse warmed up to 40 C. We managed to save the small plants and started to pay close attention to opening doors and windows whenever the sun was shining. In addition to having doors & windows open, along with fan running, we set up a swamp cooler, covered the outside of the greenhouse with shade cloth (prevents 50% of sunlight) from Lee Valley; however in the heat of the summer, we struggled to keep the temperature down below 30C and often times it went well beyond this temperature during the major heat waves. How did you folks keep the heat down in your greenhouses? How did your plants do this past summer? Any problems with blossom-end rot this summer?? Help!!!

b) Additionally, we found that blossom end rot always accompanied the fruit off of the tomato plants during the hot spells last summer. We have been growing heirloom italian roma tomatoes from seed that a friend of my mother brought with her over 50 years ago. Progressively year by year we've lost more tomato fruits to blossom-end rot. We've been told the plants need more calcium but our soil contains: sea soil, mushroom compost, bohkashi - -all which should contain sufficient nutrients including calcium and magnesium. When this wasn't successful we even provided the plants with foliar sprays of kelp and calcium regularly (Terra-flora's Magi-Cal was recommended by Westcoast Seeds). What are we doing wrong? ?? We could use some insight from the experts!!!
Danoost
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Re: growing sun-loving plants in the heat of the summer!

Post by Danoost »

The more sunlight the better for the crops you mention.

I'm concerned with your spring temperatures rising to 40C. My mid-summer, however, these temperatures are almost unavoidable. Keep greenhouses ventilated in the spring when the sun is out. Close them at night. By around April 15 we keep the doors and sides of our greenhouse open until around September / October even on cool nights. You need to keep the climate in your greenhouse to reflect the outdoor conditions without exaggerating the extremes. Greenhouses for peppers, cukes and tomatoes in our region serve two purposes: (1) keep temperatures 5-10C higher than outdoor temperatures. (2) keep crops covered to prevent blight and fungal issues. Find ways to moderate the extremes.

That said, when we had 45C outdoor temperatures last summer, our greenhouse temperatures were around 55C. I watered overhead 20x per day for 1 min to cool plants. This is not my normal watering procedure but I needed to lower temperature through evaporative cooling.

Sometimes soils may contain all the essential nutrients for plants but plants can't uptake the nutrients for a variety of reasons. Temperature, lighting and moisture levels are sometimes the issue. The main reason, however, is because the soil food web members the plants need to work with are absent. Why are they absent? Because food is lacking or the conditions are unfavorable. Sounds like you are supporting your plants by giving them the nutrients they need. But do you have adequate aeration in soil? Is the soil too compacted? Are you overwatering?

For tomatoes, why not try a few hybrid plants alongside your heirlooms and see how they perform. Sometimes heirlooms are more prone to disease. Or at least try another heirloom variety and see how it performs compared to the plants you grow from your friends mother.
rosbeal
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Re: growing sun-loving plants in the heat of the summer!

Post by rosbeal »

Hello Dan, I am asking Damien to add a photo of our home-garden greenhouse for you to review and perhaps, given your great deal of experience, you'll be able to make some suggestions to what we have already tried (as recorded in my previous post) . Just this past week even with the vent windows on the upper wall fully opened, the greenhouse reached 28 C.

Also wondering if your greenhouse plants (aka tomatoes, cukes etc) are planted directly into the soil (ground level) of the greenhouse like we've been doing or if they are planted into pots?

Our greenhouse has 3 vents in the vertical portion of the roof and we leave the screen doors (both ends of greenhouse) open when it is warm outside so air can circulate. Dan, please look at the attached photos and see if there is anything else you would recommend.

Your help is really appreciated Dan.
Kind regards, Bobby
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Danoost
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Re: growing sun-loving plants in the heat of the summer!

Post by Danoost »

I think the greenhouse is beautiful.

Grow plants directly in the ground. However, because the pathway is quite wide, you can grow plants in pots as well.

Ventilation is more important than people think. It's not only to allow hot air to vent but also to keep air moving. Plant leaves are covered with microbes that require fresh air.

The biggest challenge with greenhouses is moderating the temperature. You may wish to consider overhead irrigation to help reduce temperatures on hot days. You can buy inexpensive misters of foggers that run on a timer on hot days. I always make sure leaves are dry by evening, however, to avoid mildew and blight.
rosbeal
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Re: growing sun-loving plants in the heat of the summer!

Post by rosbeal »

Hello again Dan. Enjoyed your webinar on growing sun-loving plants. Looking forward to more on this topic especially the pruning of cukes in the future.
Right now, we've got our heirloom italian roma tomatoes planted in our greenhouse and as you suggested we've also planted two new varieties (Hungarian heart & oxheart). We'll test to see if the environment in our greenhouse is just too warm in the summer for growing any type of tomato. Right now the greenhouse does warm up a lot on sunny days but I am concerned about the heat of the summer. So as you suggested, we've added more venting windows from the sides, as we already had 3 roof vents so we're are hoping that with these additions and the open doors, the wind can blow in on all directions.
You mentioned that you formerly struggled with blossom end root on your roma tomatoes but you never described what you had to do to remedy this. You did show us a beautiful picture of your clusters of roma tomatoes without this condition. So. .. what are you doing differently now than before?
Also, in terms of irrigation, we have a 1/4 inch drip/emitter hose with emitters on 6 inch centers sitting on top of the soil. Each emitter is rated at 1/2 liter per hour. Typically we let the system run for 15 minutes each morning. Is this adequate or how do you do your watering of the tomato plants? You mentioned that you really soak the soil but then let it dry out. Is this just for potted seedlings or is this the same for the tomatoes planted directly into the greenhouse? As you suggested, we' ve set up some overhead misters for the potential hot summer days. At what temperature do you run these misters and for how long?
Looking forward to hearing your suggestions, Bobby
Danoost
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Re: growing sun-loving plants in the heat of the summer!

Post by Danoost »

The additional venting will make a big difference.

To resolve issues around blossom end rot we've improved airflow and continued to add rich compost over the years. Our composts contain mostly decomposed woodchips, mushroom compost, chicken manure. We don't supplement with eggshells or other calcium rich sources. This would be a good idea, however.

My general theory surrounding fertility is this: woodchips from a variety of trees from different regions in my area contain all the essential minerals and nutrients for plants to thrive. We make these nutrients available to soil food web members. In healthy soil that has a flourishing soil food web, organisms absorb these elements and release them to plants. Sometimes these nutrients are inaccessible to plants for a variety of reasons: soil too wet/dry, microbial population is out of balance, too cold/hot, too much or too little of a certain element in soil, etc.

It's hard to give specific watering instructions because there are so many variables. Here's a general rule: keep soil evenly moist but not saturated. Water overhead in short bursts (2 min) for tomatoes to cool on hot days but it's essential plants are dry going into the night.
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