I think you'll be fine, make sure the hoop house is staked well. Also, you may want to add a thermometer to inside it and on days when it goes above 80 inside the hoop house you should vent it a bit so the air inside doesn't get too hot.

Thanks, trudi!

I actually have a remote temperature sensor installed there which reads out to my main bathroom. That way, I can check the temperature several times a day, and it also tracks the high temp and low temp (since reset), so that I can go out and open a door if necessary.

It's not so much the highs that I am concerned about (I can vent those away), but the low temps. It will be in the single-digit lows in the next few days, and Nebraska is known for negative degrees, too!

There are a few established Russia kale plants, parsley, onions, and overwintering perennials already growing in there.

Will I "fool" the seeds into germinating, and then freeze 'em to death? Or is it safe enough?

You can increase your night temperatures a little by keeping jugs of water inside. Find some that are dark-colored, and try to place them so they get maximum sunlight. The water will warm, and hold warmth longer than the air inside the hoophouse.

The seeds your daughter sowed are of plants that will tolerate very cold weather.

Sounds like a nice set-up. For germinating seeds of hardy plants, you don't have to worry, I would think. For stuff that is already growing, Eliot Coleman of Maine (forget the name of his book) found that remay directly over the plants inside the covered tunnels made a big difference at the coldest times. In a large hoop house you will need a LOT of water jugs. Maybe some big barrels? As close to the plants as possible. Let us know how you do.

We are eating lettuce all winter with just mini hoop houses from cracked clear plastic totes. (Cracked, because we use the whole ones for their intended purpose inside the house!) I do put water-filled milk jugs inside. This year I started coloring the water to increase heat gain on sunny days. I can't compare to other years though, as we are having a mild winter.

Hepatica

Thank you, Hepatica, Trudi and Donn!

Yes, I have two of Eliot's books (and another on the way since he enticed me with hints about his compost methods that use a little clay--that I have too much of).

Unless I can add an additional purpose to them, I am not going to add any water jugs since even at close to 500 sq ft, space is so precious in the hoophouse. There are already several six-gallon buckets that often contain water that provide a little bit of temperature moderation. I also have some agribon fabric that covers some of the existing plants--chard, radish and kale.

This year I'm going to get more organized with the secondary row covers and the watering systems though.

Right now I'm playing around with the idea of winter sowing some ascelpias for my monarch waystation!

Asclepias are nice, in zone five I think that the blood-flower would be iffy, you might germinate that indoors in late winter so you have enough time for it to bloom (as an annual) but all the hardiest perennials should do fine. The common orange one can take two to three years to bloom from seed, swamp milkweed and common milkweed should bloom second year. Any asclepias, and there are so many, are wonderful additions to a habitat garden, however some of them can be pesky reseeders so lob off their seed pods before they ripen, fluff and fly away to settle and sprout EVERYWHERE.

T

I am bummed, bummed...

It's been almost two weeks now with no germination in the hoophouse. I woulda though that at least an arugula or a turnip would've poked its head up by now.

I started some turnip seeds indoors shortly after the outdoor sowing. They sprouted in two days, and then I moved the flat out to the hoophouse for the better light there. The seedlings are growing very slowly--almost in stasis.

Sorry--just being a wet blanket today. Had a small disaster with my new birdfeeder and that has me in a sorry mood.