Some of the grape growers here to avoid a damaging frost in the early spring turn on sprinklers from one to five AM. It does work, but most gardeners prefer to sleep those hours. Al

You can also spray your plants with Cloud Cover. If you have any in pots, you can move them closer to the house under the eaves or under evergreen trees. Stringing Christmas lights around them will help also.

Keep your plants watered. Frost sucks the water from the leaves and if the soil is dry there is no moisture to replace it. I use Cloud Cover every year along with keeping the soil moist.

Penny

Overhead watering to warm up plants only works if you keep doing it all night long, as Al said, so what you are doing is a waste of time. You would be better off covering your plants with old sheets or burlap, and tenting them with stakes so they don't touch the plants if you want no leaf burning. This works well enough if you only get a few degrees of frost. If a serious freeze is projected, you will need to add christmas tree lights or such under the tenting, and tent in a manner that you trap the heat, rather than just covering the tops of the plants. Agricultural row cover cloth works very well also, and can be left in place for days or weeks, as it still admits light.

A better strategy for growing too tender plants is to grow them in containers which can be moved under cover or indoors, or locate them in the garden where they will get overhead protection from roof eaves or evergreen trees. For smaller plants, you might also find that placing them amongst large boulders that get sun in the day may give an extra heat effect at night, as the heat reradiates away.

Last year, during the bitter freeze, I was out every night putting "Frost Cloth" covers over 4 big containers (and taking them off in the morning). All the plants survived, but my hands did not - I got a terrible case of eczema and am still battling the remains of it. The doc says the cold weather probably did it (we were also out there one night wrapping pipes), although I didn't think to ask him about the frost cloth - it clung to my hands in a kind of irritating way. For me, I've decided to not go all out like that this winter, but I can see that you really care and want to save your plants. The frost cloth covers were kind of expensive, but I think they really helped save those plants. I got them at a local nursery. They were round, with drawstrings at the hem, and came in different sizes.

I have wire cages around my citrus -- to keep the deer from eating them. Last winter I wrapped silver insulating sheets around the outside of the cages, then covered the tops with big towels for night. I had thought the heat-mass of the concrete stairs would protect the potted palms, but it didn't and they had major damage. I'll need to do something to protect them this winter.

Thanks for the input here, folks. I think I'm going to have to check out that Cloud Cover. I've never had a Princess Flower make it through the winter unscathed, but perhaps this year... :)

-Ray

I'll share my little invention that I use in my citrus. I start with a glass jar candle, like the little ones that are on restaurant tables sometimes. The one's I use are about 2 1/2 inches across and 3 inches tall.
Next I take a 1 pound coffee can with one end out, the regular way you open a coffee can. Then I punch several holes in the sides. I'd say about 6 neat the top (end with the end still in) and 6 two thirds of the way down. This is with the open end as the bottom so it can sit over the candle.
I set these out, with a little stick, maybe the size of a pencil, under one side so that the can is tipped. This lets a little more air flow through the can and gives air to the candle.
The cans do a couple of things. First, when it's 30 degrees out, the candle wax will be so cold that the wick will burn a tunnel right down through the candle and most of the wax won't burn. So the can keeps enough heat in that the wax can melt and the candle burns the way it should. Next they act as little radiators. The idea here is to heat a lot of air just a little. The heat from a candle by it's self would all just go straight up and not help the tree. They also keep the candle from blowing out in a light breeze.
I do this with about 120 candles for 100 citrus trees. Of course being out at 2:00 in the morning, freezing my fingers, lighting candles, is not a lot of fun, but it is a rather pretty sight.
Be careful for fire hazzard.
Do not place on or near mulch, branches, or other flammables. Clear a spot so that they are clear of any material that can burn.
Do NOT put these directly under the tree as that will be to much head and will "burn" them.
If you do this, you should monitor them closely. I will put a movie on, make hot tea, set a timer, and check them once per hour after I have them set.
I got all my citrus through last years hard freeze. We had 2 days of more than 12 hours of below freezing temps with a low of 10! and 2 more days with lows of 12 and 15. Nasty cold for citrus. The limes didn't fruit this year (the trees are ok though) but everything else did.
I also run irrigation water while doing this. the heat from the water helps too. Start irrigation water early, several hours before the temp drops below freezing, to build heat in that area. If you wait until it starts to freeze, it's to late.

What a wonderful idea! I have several of the jar candles. I just have to find some cans that are the right size. We get our coffee in plastic nowdays. It is hard to believe that a small candle can protect a large tree, but they do put out a lot of heat and just a few degrees can make a big defference. My trees are too far away for christmas tree lights(I don't have that many long extention cords), the candles might really do the trick for my 4 small 5 gal sized trees. Thanks so much for the idea
Donna

I keep a candle, matches and a can in my car and in my home earthquake kit.

This just might work for the Date Palms on the front steps. How far away do you place these candles?

how far away. I'd say about 4 feet. If you only have one or 2 trees you will need to use maybe 4, spaced on all sides. If there is a wall or up against the house, you don't need one on that side. In a group planting, I place one every other tree all around the perimeter. then scatter a few where I can within the interior of the planting.
AGAIN, BE CAREFUL ABOUT FIRE HAZARD. That would be a really bad day if you had a fire.
Remember, water running in basins under the trees is a tried and true help also.