Hi Sheila,

I don't think the Agribon-19 will necessarily give you 8 degrees of protection if doubled, but it should give at least 6 or 7. A lot depends on how warm the ground still is (this works in your favor since this is the first big cold spell of the season and the ground remains relatively warm), how windy it is (uh oh....this front will be bringing the wind!) and when you cover up the plants.

When I use Agribon-19 doubled, I do expect 8 degrees of protection and likely I get it, but it just isn't guaranteed.

To ensure your Agribon-19 will keep your plants as warm as possible, put it on the plants long before sunset. You want for it to capture and retain as much of the daytime heating that has warmed up the earth as you possibly can. I like to get the Agribon on the plants shortly after lunch time while the earth is nice and warm. With the row cover over the plants, more of the heat will be retained.

Be sure you weigh down the edges of the fabric as completely as possible. I normally use metal fence posts or pieces of rebar laid along the edges of the row cover to ensure the wind doesn't lift it up and expose some plants. I have used the U-shaped metal landscape staples that often are used to hold landscape mulch fabric in place and they work well enough but they put holes in the fabric (which isn't the end of the world). You can use anything that will hold down the edges of the fabric in the face of strong wind.

Your cool-season crops normally start to show damage when the air temperatures drop below 24-25 degrees. Most of them can tolerate some amount of frost and with some of them, like kale or brussels sprouts, exposure to cold weather actually improves their flavor. Most of the crops you listed would tolerate the temperatures you're expecting, and they might even tolerate 25 degrees with little to no damage without being covered, but.....

The big "but" in all this relates to how much cold exposure they've had prior to this cold spell. If they've already been exposed to a lot of near-freezing temperatures, they likely have hardened off some to the cold and are less likely to be damaged even if uncovered. However, if your weather has been relatively mild and warm and they have a lot of tender growth that has little prior exposure to freezing temperatures, they could suffer more damage if left uncovered.

Based on the plants you listed, I wouldn't expect damage if they are covered with a double layer of Agribon-19 unless your temperatures fall significantly lower than expected. If you were to get sleet or freezing rain, all bets are off.

One way to help the plants stay even warmer is to put containers of water alongside the rows of plants and cover the containers with the row cover. I like to use 5-gallon buckets and cat litter buckets, and after saving them all for the last 15 years, I have quite a large supply of them. However, in a pinch when we were having either very late frosts/freezes in spring or very early frosts/freezes in fall and I had more rows of crops than I had buckets of water, I've even placed a case of bottled water (16 or 20 oz. bottles) out on the driveway or concrete patio all day to let the water in the bottles heat up and then I've laid the bottles horizontally on the ground alongside the plants right before I covered them up. The bottles function as solar collectors and help keep the ground and surrounding plants a little warmer.

I've used Agribon-19 for at least a decade and I normally don't see damage on plants covered with a double layer of it until we hit roughly 24-26 degrees. It depends on the other factors above, and obviously in the fall I've seen less damage due to the warmth of the earth. In February or early March when the earth is a lot cooler, a double layer of Agribon-19 might only give 6 degrees of protection. I've always wondered how much of a difference wind chill makes, because I know that I'll see more damage on very, very cold nights if the weather was windy than on wind-free nights with the same temperatures.

Remember, too, that even if your plants were to be significantly damaged by this week's cold weather, they are likely to survive. I'd had fall garden plants freeze completely to the ground in 16-18 degree weather, and then almost immediately begin putting out new growth within a couple of days of the date that the freeze damage occurred. However, if they've been exposed to 10-12 degree weather and they freeze, they may die, although I've had Swiss chard survive down to the mid-teens uncovered, and it has survived single-digit temperatures under two layers of Agribon.

Last year, using a double layer of Agribon-19 and cat littler buckets filled with water, I was able to keep lettuce, collards, turnips, and other winter greens growing and producing until we had an 11-degree night. After that night, everything in the ground froze, but the lettuce in containers near the concrete patio survived all winter. I did have their container (which is a black rubber cattle feed trough that sits elevated a foot or so above ground on metal legs) surrounded by cat litter buckets filled with water and covered in a sheet of black plastic to help the water buckets heat up and retain the heat). On extra cold nights (anything with a forecast low below 20 degrees), I threw a couple of moving blankets over the floating row cover for extra protection. At about 16-18 degrees, the plants in the trough suffered minor freeze damage if they were covered only by a double layer of row cover, but with the blankets over them on those really cold nights, they weren't damaged until the temperatures got down to 11-12 degrees. It is the first time I've kept lettuce alive all winter outside, and we were able to harvest and eat the lettuce and mesclun greens from that container until about April. By the time they were starting to bolt, the spring-planted lettuce was large enough to harvest and use.

It is extra-important to make sure there's no where the wind can blow the fabric off the plants. I had the fabric rip loose and blow around in a windstorm one night last year, and the plants in the area of the rip had freeze damage while the covered plants had none. The damaged ones were half covered because only part of the fabric came out from underneath the pole that was laid on top of it, but being half covered wasn't good enough.

Hope this helps,

Dawn

Thanks Dawn
Helps a lot. Tells me I goofed up when I covered them to protect from the 35 and 36 nights. Would have conditioned them a little but oh well you live and learn. I will cover them again tomorrow and we'll see what happens. Sheila

Well I covered the plants with 2 layers of agribon It is very rigged. I do not have pvc pipe so used small shepherd hook basket holders. Wish I had more of them. stuffed other things under there to help hold it up but it is still touching some plants. Best I had to work with. I think the air could probably come through in a couple of places so I covered all around the outside with hay. Hope it works. Next year I will have hoops!!

Sheila, I hope the plants made it through this cold spell. I love my hoops! Back in the spring when we kept having one or two nights a week where temperatures were near or below freezing, I left the hoops in place and I put bird netting over them to give the plants some protection from hail. I left the bird netting on the hoops from April through very late May or early June. I finally had to remove it because the tomato plants were hitting the bird netting and about to start growing through the netting. Tim had made extra tall hoops for the tomato beds so I did get to leave them covered until the plants were a little over 3' tall. When cold weather threatened every week, I just pulled row cover over the hoops and weighed down the edges to hold it into place. With the infrastructure of netting-covered hoops already in place, the process of covering up the plants went pretty quickly even though I was covering a huge area. I didn't have hoops over the rows of corn and keeping them covered for the last two cold days was pretty hard because they were knee-high by then and I was worried the heavy frost blanket with a lot of wind might damage but the plants, but it didn't.

Normally I just let floating row cover float freely as it was designed to do and that has worked fairly well except with the most delicate of crops like tender young lettuce plants. At least it always worked with Agribon. After I bought the significantly heavier DeWItt frost blankets that give 10 degrees of protection, I developed a deeper appreciation of the hoops because a single layer of the frost blanket is fairly thick and heavy and a double layer is even more so. I don't especially like putting it on young, tender plant growth without hoops.

I have about 40 containers of plants in the greenhouse now---everything from tomato plants to ornamental sweet potatoes to brugmansias to lantana and cosmos. Since the greenhouse is unheated (I could buy a heater and put it in there but I don't especially want to do that because it just would mean a higher electric bill), in midafternoon when it was all toasty warm in there, I dragged the floating row cover out of the garage and put a double layer over all the plants in the greenhouse. So far today, our low temperature at our house has bottomed out at 22 so I don't know how the plants in the greenhouse fared, but usually I can keep them alive until the low temperature outdoors hits18. Obviously there were no hoops over the plants in the greenhouse, but these also are not young tender plants that might break under the weight of heavy cover---they are tough old survivors.

I did resist the urge yesterday to run out and dig up all the plants that still were blooming in the garden (lantana, scabiosa, cosmos, autumn sage (which is perennial so I wouldn't actually have dug it up, of course), four o'clocks, many kinds of zinnias, moss rose, angelonia, angel's trumpet, basil, etc. I had toyed with digging them up and potting them up into containers to keep them going a bit longer because I just hate not having a lot of flowers in bloom in the winter. Of course, doing that would have made no sense at all since I would have had to prune them back, thereby cutting off all the flowers.

I had intended to harvest the catnip so the cats could enjoy it, but I forgot. When it warms up today, I'll go out and cut down the frozen catnip and bring it inside so the cats can enjoy it. They won't care that it froze.

Dawn

Well they made it through and looked great today. Tonight is suppose to be a little colder. Working on getting hoops ready before it does this again next week. Saw some using black water line over rebar but didn't say what to clamp it on with.

Dawn
You talked about hardening them off to the cold. Monday the forecast is 36. Since I have covered them do you think leaving them uncovered for that is too cold if it frosts