Saturday, August 3, 2019

Observations on my Greenhouse Experiment

I've only had the greenhouses operating full scale for the past two months. But already I've been able to make several observations. 

..... Covering. Plastic film vs greenhouse tarp. The plastic film allows more light into the greenhouse than the tarp. But the plants don't seem to be having severe problems with that. I have zucchini, cucumbers, tomatoes, peppers, eggplant, and lima beans growing and none seem slow growing or stunted in any way. None appear to be abnormally stretching, trying for more sunlight. But then, tropical sun is quite intense here. Apparently enough sunlight is getting through the tarp. 
       The tarp is definitely a lot stronger and tear resistant compared to 6 mil poly film. I accidently dropped a 2x4 against the tarp and there was no damage that I could detect. Wonderful! 

..... The veggies I opted to grow are growing faster and larger than they did when I grew them in my standard garden plots. I'm guessing that the higher daytime temperature and protection from wind contribute to that. High humidity is normal here, but it is probably higher inside the greenhouses. 

..... Less pest problems. I'm finding a few grasshoppers that managed to sneak in, but not much else. Most importantly, no pickleworm moths! 

..... Watering. Since rain can't water the plants for me, I need to provide the water that they need. By trial and error, I've determined that each greenhouse needs close to 100 gallons of water weekly. 

..... Lima beans. The limas look great! Best I've ever grown. The extra heat seems to suit them just fine. And I'm seeing lots of pods that appear to be developing beans inside them. Time will tell if I actually get a crop of lima beans.  

..... Cucumbers. I'm growing only parthenocarpic greenhouse varieties. Some are doing better for me than others, though all have produced some cukes. The best ones so far are Saber, Nokya, and Socrates. 

..... Zucchini. In the past I've never been able to produce a single harvestable zucchini. To date I've harvested 28. Yes, 28. Yikes! I'd call that a success. I'm trying 3 varieties : Desert, Golden Glory, Black Beauty. Desert has been doing fantastic. Golden Glory is so-so. Black Beauty isn't worth growing again. Initially I let nature take its course, and without much fuss, the plants produced some zucchini. But as the plants aged, I saw more aborting. So these past 10 days I've been hand pollinating, resulting in more squash consistently setting on the plants. 

..... Powdery mildew. This is a real common problem where I am, so I've been expecting it to rear its ugly head. It's been 2 months since I started this experiment, and I'm just now seeing some powdery mildew on the zucchini. I haven't done anything to try to prevent it because I wanted to see what would happen and what I would be up against. And I needed a baseline to work from in order to develop some prevention methods that actually work. Plus I wanted to know which varieties had the best resistance to it. 
      Now that I'm seeing powdery mildew, I'm instantly removing any leaf that shows the beginning dots. This will only forestall the inevitable, but should allow me to harvest some more squash before the plants succumb. I haven't seen mildew on the cucumbers yet, but I fully expect to see it soon. 


  1. Excellent post. I'm very interested in your greenhouse experiment and observations, because we've been discussing a greenhouse too. No pickleworms?!? That's a huge encouragement! Have you been recording the temps in the greenhouses? That's the thing I've been most dubious about. The other day the soil in my raised bed adjacent to my hoop house was 104°F, so no wonder plants were struggling there. The extra heat in a greenhouse might be too extra for my part of the country.

    1. Leigh, I haven't thought to record the daily temperatures. That would be a really good idea. Next time I'm in town I think I'll pick up one of those hi/low recording thermometers. I'll keep you posted.

  2. Hi! I've dealt with the powdery mildew, it will spread to the cucumber pretty fast! Switching to a drip line helps tremendously. You can also spray the plants for a home remedy I use 3 tablespoons baking soda to 1 gallon of water! Hope that helps :)

  3. Gerty, I agree.....the cukes will get it too eventually. I'm expecting it.
    As for watering, I presently am using a hose to flood the soil surface. No water gets the leaves wet. In that I have no electricity within 600 feet of the greenhouses, I can't use a pressurized drip irrigation system. Our small house pump cannot drive water that distance. And setting up a water tower would be more expensive than it was worth. Plus I prefer to keep things simple.
    I've yet to determine an effective preventative/control for powdery mildew. I've already tried 3 suggested remedies: milk, baking soda, and urine. None were very successful, although daily diluted stale urine worked the best. This makes me think that possibly frequent applications of compost tea sprayed on the plant might help. Maybe surface microbes will have a bearing on the problem/ solution. That will be my next experiment-- various types of compost teas sprayed on various schedules.