what you think is the actual amount of frost protection a floating row cover of that weight will provide

Well, I have used a "light" row cover for stuff other than toms. Does boost temps inside the mini-hoop which also warms soil to provide latent heat at night. Very much dependent upon cloud cover and wind velocity, however. They are NOT as effective as W-o-W for frost/freeze protection. An extended period of below freezing temps and little sunlight will result in unacceptably cold temps for tom plants inside hoops. I would not hesitate to use them, however, to provide higher than ambient temps for toms (and other stuff) when ambient temps are not likely to dip into the low-mid 30's for a significant period of time. Would not bet the farm on them because weather aberrations (in NE US) now seem, well, not to be aberrant.

They are NOT as effective as W-o-W for frost/freeze protection.

Agree that you will get much better protection from the WOWs. They protect even in a hard freeze. You'd get a better effect even from plain plastic wrapped around the cages to create a mini-greenhouse effect. They both have the added benefit of blocking the wind.

And the wind and its effect on temps is the limitation when using Reemay and similar row cover. Reemay claims 5-10 degrees with their heavyweight "depending on the wind effect". So medium weight would likely be somewhere in the less than 5 degrees. Of course you could double wrap with it for more protection but there will still be cold air exchange.

If you can afford to lose the plants then it is worth the experiment but better methods are available.

Dave

Agree with the above 2 comments.
But in the case of emergency, if you have long rows, and you cannot afford WOW for every plant, perhaps row cover can be helpful.
I make small cages from rabbit fence and wrap it with bubble wrap. It works like WOW. These devices mostly prevent wind blow and rapid cooling. Also as an open mini greenhouse can help the soil temperature to warm up a bit and stay warmer. for a longer time when the temps drop.

I'm talking about planting during a few week period before the last frost, but in a period when daytime temps are generally from the 60's to the 80's and while frost isn't a certainty, it is a possibility. Not at all likely the plants would be exposed to below freezing temps for more than 5-6 hours, and maybe only once or twice during that period. Only takes once to kill them, though.

I am familiar with the concept of the Wall of Waters, although I have never used it. How practical is the applicability of that on a scale of 150+ plants or maybe a few more? Any particular version of the WOW that you recommend? I forgot to mention, also, that these plants will not have individual cages for support, they will have a Florida Weave like we used last year.

WOWs wouldn't be at all practical for that many plants. Personally I wouldn't risk that many plants that early. The loss overhead could be substantial. All it takes is one exposure to kill or grossly stunt and damage the plants and you could lose them all.

We plant 150-200 plants as well but only push the planting envelope with about 15-20 of them. The rest are planted after last frost date. That way we have a number we can work with protecting if problems do arise, a risk level we can afford to accept and replace, and we get the advantages of early production if all goes well.

Nothing says all your plants have to be or even should be planted at the same time. :)

Dave

That 150+ plants is actually only slightly over 20% of the ones we're going to plant this year. They're the varieties that we primarily took to a few local produce auctions last year. The difference in price they were bringing between early July (sellers who already had tomatoes) and mid to late July (when ours started ripening) was significant, though. I'm willing to incur a little risk for the potential great reward, I just really wanted to know how much protection the medium weight floating row covers provide since I've never used them before.

i've planted several hundred tomato plants in black plastic and low tunnels covered with agribon19 in mid-april here 6a. it works very well. staking is a problem with this system.

Randy, did you leave them covered for a period of time, or just when it looked like there was going to be a frost that night? What state are you in?

VA. I covered them when i planted them and uncovered them june 1st when i was sure there would be no more frost. getting ripe early tomatoes this way is still weather dependent but you will be ahead of any other outdoor grower not using covers.

I too leave WOW way past their needed time. If you can create wind barrier, i.e. plastic walls with stakes and 2 mil clear plastic to add to your row cover protection? Here in windy Chicago, wind is more damaging than light frost, I have found it beneficial to spend extra $ on wind barriers.

Randy, were you drip irrigating your plants or letting them just draw from the moisture in the soil and get rain that soaked through the floating row covers? In the area where we'll be planting these, we didn't do any irrigating last year and the plants did really great, had plenty of moisture for the whole growing season. How much rain can really get through the floating row covers?

How much rain can really get through the floating row covers?

The light Agribon row covers I have used are a bit hydrophobic, at least on first-time use. What I did to help water permeability on these was to soak the things in water for a few hours before erecting the fabric. The stuff seems eventually to permit almost all water deposited on its surfaces to penetrate the fabric and find its way to the soil underneath.

i put t-tapes under the mulch plastic. the row covers provide wind protection. its common to have late may frost here which is why i wait. otherwise i want the wind for pollination once the plants start flowering.