If they are the old fashioned kind, then they'll be fine! Even if it's snowing, the part under the ground, which is the really important part, will be OK. Mine look like wilted lettuce above ground right now...It's been colder here over Easter than it was at Christmas, and today it's snowing! I'm waiting until the snow melts and it warms up a little, and then I'm going to cut them down to the ground, and wait for them to put up new foliage, which I'm sure they will do. It's early enough in the season that they'll recover without skipping a beat. I had a really big one (it was about 4' high and 4' around, like a big shrub) that got very damaged from a bad wind storm a few years ago - many of the stems were broken and the plant looked awful. I cut it down to the ground, crying with every cut, and it grew back up again in about 3 weeks, and even put out new flowers! These plants are very hardy - almost impossible to destroy. A little late winter weather will not kill them.

Does the radiator heat at all? If theres a lot of air in the pipe you sometimes have to wait a minute. Do you have the makeup water turned on when you're bleeding the air?

Here is a picture of the source water line for the boiler feed up there by the rafters. The tap is fully open. What is that first valve to the left of tap? Note is has a little lever on top pointing horizontally to the right. To the left of that is another valve with a different type of lever, this valve also has an outlet running down to the floor so I'm guessing it's an auto overflow valve of some sort. Can anyone tell me by looking if that first valve is open or closed by that little lever? I'm hesitant to even touch it for fear that water will start spraying everywhere.

glorifiedb, thanks for posting this question. I am experiencing the same situation in my house recently. I have hot water heat, large cast iron radiators. I have bled the air from all of them except the one in the kitchen whose bleed valve had been painted over by the PO. The kitchen one heats up though, so I don't think it's an air in the pipes issue. The kitchen radiator isn't one that "bongs". This is our third winter in this house, and the first winter where I've heard the most banging. The only thing we've changed this year is my husband put pipe insulation around the pipes leading to one radiator (the front hall's radiator). Here's an example of banging: heat goes on at 7am (we have programmable thermostats, two zones). It shuts off at 9am. The radiators do retain heat for a long time. Around 10:30am, the living room radiator (which is about 10 feet long) will give just a single "bong". It always comes from one end of the radiator, at the pipe when it goes down into the floor to the basement. Another difference is that this is the first winter we've lived here where we've had spans of cold weather for a week at a time. (We're northeast of Boston). The previous winters seemed to have more variability from day to day. mightyanvil, it sounds logical that the pipes are expanding and contracting going from cold to hot, and vice versa. But would this cause only a single "bong" at one point of the radiator? I can live with it, except I'm worried that it is a precursor to a serious (=expensive) problem developing. Is it something I should get a plumber in to nip in the bud? Could it possibly from having sediment built up into the pipes from sediment-filled town water as I bleed the air out and new water comes into the system? Our city had a major water main break at the end of 2007 which then sent sediment-filled water through the city. Should I be draining and flushing the system every year to clear it out? Thanks in advance!