The answer to pretty much all your questions is yes.

The Silex set fruit because parthenocarpic varieties set fruit without pollinating the ovules. Non-parthenocarpic flowers with abort if the ovules are not pollinated.

Yes, some degree of humidity control is needed to keep pollen from clumping. Yes, many varieties will fail to self-pollinate in cool temperatures; however, there are varieties adapted to pollinating at cooler temperatures than typical.

Yes, tomatoes need wind to self-pollinate naturally or require bees to vibrate the pollen out of the anthers and onto the stigma. The bees are harvesting the pollen for protein and some of it falls onto the stigma rather than the bee's belly. Some growers keep colonies of certain bee species in the greenhouses.

Most hoophouse growers shake the plants daily to effect self-pollination. This can be done by beating the suspended support cords or the overhead horizontal support with a broomstick as you walk thru the hoophouse. Or you can use a battery operated vibrator on a stick to tease the flowers. Or you can rely to some degree on high volume ventilation fans creating sufficient breeze to rattle the blossoms as they would in a wind.

Sadly my low tunnel is not even large enough to walk inside, an adult would have to squat down to get in there (usually my wife does this when absolutely necessary). But I guess I could just keep an eye on the plants for opening blossoms and give them a shake or tap with a stick every now and then. Maybe I could tie a string running from all the plants and through a hole in the ground outside, then tug that every now and then to shake them? :) Do the flowers need to open to be pollinated, or does it take place even before they open?

Not sure how to handle the ventilation, since the tunnel is nothing but a flexible plastic sheet over pvc hoops, with all but one side buried in the ground. I am wondering if I should put some eyelets on the top of the tent to let the fog out, but I worry that I will drain heat out as well. As you can tell, it's a rather low-tech operation.

I'm new at this low tunnel thing myself (1st yr.). I've seen some use blossom set but I think it just prevents blossom drop and does little to pollinate. Is there a minimum soil temp for transplanting? or just day-night temps? I will be using a breathable material for a cover over arched welding rods. How much frost protection should I suspect? Will I be able to put them in the ground 3-6 weeks before my last probable frost date?

To be honest I only planted under the low tunnel after the last day of frost, but before average temps were warm enough for tomatoes to grow well. I think that a non-permeable skin would give a good amount of frost protection,and probably raise temperatures at night by at least 5 degrees if you use water bottles as a heat sink like I did, but I never measured exactly how much warmer it was in the tunnel. Maybe someone can give us an estimate?

My goal is to get my plants in the ground as early as possible without danger of death by frost rather than pollinating in the tunnel. My most probable last frost date is around April 20th. I usually plant around May 1st when my neighbors do. I read somewhere that blossom setting depends on ground temperature as well as air temperature. I will be using black plastic mulch in an attempt to assist the weather in warming the soil. I will be watching the weather for 60*f days and 40*f nights. I plan on using an opaque breathable cover to allow for light and air circulation (Co2) and prevent frost damage. I guess my question is will I be able to plant on the vernal equinox (March 20th) with this setup, and be safe from frost? or will I be better off with 4-6 mil. plastic? Is my best bet to use the thin cloth and keep the plastic handy? I've probably just answered my own question but if I'm doing something wrong please advise. I plan on digging a trench when the snow is gone and the soil is workable and storing the dirt under a tarp so that I will be able to plant regardless of spring rain/soil conditions as last year this was a big holdup. (way too muddy for about 3 weeks straight).

hardclay

Here are SOIL temps recommended for planting various crops, though I can't find the link that I got them from. And they may not be precisely optimal, but you probably wouldn't go wrong using them as a guide.

40 degree F soil - Plant endive, lettuce and pea seed
45 degree F soil - Plant carrot, radish and spinach seed. Set out cabbage transplants, potato starts, and onion sets
50 degree F soil - Plant beet, parsley, parsnip and Swiss chard seed
60 degree F soil - Plant snap bean, sweet corn, cucumber and turnip seed. Tomato seedlings
65 degree F soil - Plant lima bean seed
70 degree F soil - Plant okra, southern peas, squash, pumpkin and watermelon seed. Set out eggplant and pepper transplants
75 degree F soil - Plant cantaloupe seed. Set out sweet potatoes.

Thanks a bushel Anney;
That's exactly what I'm talking about! I'll be checking for these soil temps while watching for those day/night temps. While on the subject of weather did you get any snow where you are? I'm looking at a radar image that looks most unusual!
Ken

Ken

I keep those temps in my garden planning info., along with this link:

http://www.georgiaweather.net/

If you choose the tracking station closest to you, a window will open that has all KINDS of weather information for Georgia by region, including soil temperatures. Just click on "7-day Summary" in the right-hand column, and temps are recorded for 2", 4", & 8" soil depths in the area, along with some other information. You can change the dates if you wish.

Yes, we got snow yesterday afternoon, enough that everything is covered. It looks lovely but will melt as soon as the cold snap ends, I'm sure. It's been pretty cold these last few days, at least for this area.

Too much nitrogen fertilizer, nighttime temperatures over 70 degrees F., low temperatures below 50 degrees F., irregular watering, or insects such as thrips may result in poor fruit set. If placed where less than 8-10 hours of sunlight can reduce fruit set.

Low or high humidity effects pollin viability.

Ventilation is important. Stale air can effect pollination but also lead to diseases. Air movement is important to pollination; typical vibration of the blossom. You can physically vibrate the plant for 3-5 seconds several times per day for several days to ensure pollination. Even a stick tapping a thick stem will work.

Leave the tunnel ends open. It is not necessary to close the sides. The temperature desire is primarily directed at the top growth, especially growing tips.

Row covers will provide frost protection to a point if you really want to push last frost dates. Plants must still be hardened off to withstand daytime sun as well as temperature fluxuations.

If the air temperature outside the low tunnel was 60° what was the temperature inside the tunnel? If it is sunny outside, it might raise the temperature of the air inside the tunnel high enough to affect pollen viability (especially with it being humid in there.)

As organidan says, leave the ends open. If you expect cool weather, you can always close it down more.

Bets