Dave, probably around December. It gets very cold, but rarely below 32

They feel frost, they are doomed. Indeed. As long as the ground is warm, covering them with something when a light frost is expected is the obvious fix. Plastic tarp, big blanket, even a couple of sheets. Whatever. Just hold in the warm air coming off the ground. Seal the edges so cold air can't get in. DO NOT just wrap the plants. The heat is coming from the soil. Whatever you cover needs to include the soil underneath. Fling off the covers when it warms up.

The architecture will depend on how you have them growing. Are they bush beans close to the ground, or are they vertical on trellises?

They are in a container, and they are short bushy plants. One is slightly vining, but does not have a trellis. Worried that the vine would freeze and damage faster than anything else. However, the container is large and not easily moveable, and could not go inside. The pot is 2' by 9" I think

I could possibly move it to the garage, as I have a small grow light. But I'm afraid it won't get enough light with the grow light. But if it'll work, it's better than nothing!

On the cold nights when it is going to get below 39 degrees and little wind, you would want to move them into the garage. Once it warms up put them back outside. The cold weather will only last a couple of days and then warm back up. Temperatures in the 50s should not hurt them. If it gets down into the low forties the plant will slow down. Just keep a close look at the weather and remember they can be wrong by 4 or 5 degrees. Even being close to the house will raise the temperatures a few degrees. On windy nights frost will not form.

On a side note, the meyers lemon you have will not suffer damage to its fruit unless it gets below freezing. I have heard you are ok on lemons and satsumas as long as the temperatures stay above 28 degrees.

Here's what I would do: create a frame for the container using 10' pvc piping, cheap stuff. In this pic, the pvc is held in place by the wood frame of the raised bed but you could use four cinder blocks placed around the container.

Buy an old sheet at Goodwill and some of those old time Christmas tree lights, big fat bulbs. First lay the string(s) of lights on top of the soil, then drape the sheet over the pvc, hold in place with binder clips (from Staples) plug the lights in on those cold nights. Raises the temp under the sheet significantly. I did this all last winter with about a dozen containers of tomatoes. Worked great. Good luck!!

Without moving containers into a warmer place, protecting from a frost is harder than protecting plants in the ground. Why? Because the bed itself can freeze because of the cold air on the sides. But if your climate is anything like mine, the frost happens just in the early morning hours. Not all day. So you need to protect for a few hours, not for a few days, and for a large bed, only the edges of the bed will get seriously chilled. If you can get them in the garage for those few hours, the plants certainly won't miss any light.

That being said, I'd just get a big tarp and gently throw it over the containers, anchoring and sealing it it on the ground around it. As noted, a light bulb underneath will add some heat to the air you've captured there. Just one incandescent will do it, but keep it from touching the plants. Let's not turn this into a major construction project. The plants may get compressed a bit, but they'll recover.

I mildly disagree about the effect of wind. If the soil is moist and the air is dry, wind can cool it well below air temperature. You can easily get frost when the air temperature is above 32F. But the wind can also circulate air layers, preventing a layer of especially cold air.

"....just get a big tarp and gently throw it over the containers, anchoring and sealing it it on the ground around it."

Do not let the plastic tarp touch the plant. You need some mechanism to keep the tarp from touching the plant leaves/stems etc.

"Let's not turn this into a major construction project." Dan, if you are referring to my post above, that is not something I consider a "major construction project". However, to each his own. YMMV.

In a container? How many bean plants are we talking about? You have to balance effort and time with reward gained. Protecting a 30' row of beans is worth the work but is it really worth the extra effort to protect a few plants for a tiny amount of production? And if your frost isn't until sometime in Dec. then they have 6 weeks of production time left anyway.

But if you really think it is worth it then just stick a tall stake in the middle of the pot and throw a sheet tent over pot and all when it gets cold.

Dave

As to "a major construction project", I look at this thread as a what can I do NOW question. A visit to the hardware store and Staples, carting back cinder blocks and PVC, digging out Christmas tree lights, followed by cutting the PVC and erecting is, for a NOW project, kinda major. Unlikely it'll be done by tomorrow morning. I like your design, and it could be useful in the long term, but the long term lesson here is probably not to plant beans so that you'll expect to harvest in November, whereby you'd not need such a structure for this purpose again. A structure like that makes better sense for an organized effort to extend the season, rather than an emergency need.

Points taken Dave and Dan. BTW, pvc comes in 10' lengths, no cutting required. But I see your point that what I find easy to accomplish could be a challenge for someone without a truck. This discussion has good merit and I, for one, enjoy the discourse. ;-)

Dave's right.....stick a pole in the 2' container and toss a sheet over it. Carry on.

" but the long term lesson here is probably not to plant beans so that you'll expect to harvest in November, "

Excellent point Dan. I'll add - and plant enough of them to make it worthwhile doing.

Dave

But Mary, thank you for pointing out that 10' lengths are convenient for doing this kind of thing. It is cheap stuff. An arch like that would make a convenient ~6' spread. I can see a design like that for my squash row covers next year. Not entirely clear though. How do you keep them from falling over? I see strings tying them together, but that's not going to keep them from collapsing inward. Maybe a stiff wire brace along the top is the way to go.

Hi Dan, The string is really for the tomatoes to climb. I use mosquito netting over the top (the army navy store has the perfect product for that size bed, I think they were 6'x4'. I've broken those down now and am switching to in-ground planting) once you place the netting, and secure with the clips (I bought pricey clips originally that look like a short piece of pvc with a vertical space cut out, I'll try to find a pic) it helps to hold them in place but they *can* go cattywompers on you. Adding a brace is a good idea.