It would be of great help if you posted pictures but the most likely thing is frost/freeze damage. Do the leaves look water soaked? if so your plants are suffering from freeze damage it is to early to plant them. Plastic covers do provide some protection but that amount can vary a lot depending on your set up. I have an insulated homemade cld frame and I get between 5 and 15* of protection based on how warm it was during the day but a single layer plastic sheet might only provide 1/2 - 2 * of protection.

I hope you have more broccoli seedlings indoors becuase it is a little late to plant those but you can start the lettuce again and it should be fine if you transplant it in a couple of weeks.

hope this helps and please post pics becuase you could have something else like cutworm or slug damage.

Thanks for your reply. I don't have any pics and won't be able to take any before dark, but yes, the leaves look water soaked.

That's crazy that the sheet only provides about 2 degree of protection. Really? I assume you mean overnight, right? Because during the day, it's certainly more than a couple degrees warmer under the sheet.

Mel seems to say in the Square Foot Gardening book that a little plastic cage can buy you a couple of weeks' head start on the growing season. But it seems like a couple of degrees temperature difference wouldn't really buy you much of anything at all in terms of time. Are the plastic-covered hoop houses more useful in the fall for extending the growing season, rather than in the spring for enabling early plantings?

I'm really very interested in extending my growing season. I don't have the means to build a heated greenhouse on my property here, but I'd definitely be up for building a more complicated plastic enclosure of some kind. I actually just ordered the Winter Harvest Handbook, which looks to have some information on double sheeted structures that create some kind of air gap in between--is this more what I ought to be looking at if I want to plant things early?

Also, it just occurred to me that maybe Mel is only referring to being able to *seed* things a few weeks earlier with some plastic sheeting, as opposed to being able to *transplant* things early--is this what I was missing?

Thanks for any & all help. I'm excited to start my garden, even if it is off to a bit of a rough start.

2 mil plastic will only keep the frost off. If you are well below freezing you'll want to throw a sheet or sleeping bag or something over as well.

Dan

Ok well it sounds like your seedlings got nipped by frost. I would start new seeds indoors as soon as you can and wait till the danger of a hard freeze is past below 28*. As far as season extension you don't need artificial heat to be successful. There are many ways to extend the season. I will tell you about some of the methods I've used.

Simple Methods.

1) soil warming: Even after the danger of frost has passed warm season vegetables can't be planted. You have to wait till the soil warms. One way to avoid this delay is to place black plastic over the soil and secure it to the ground with heavy stones several weeks before planting when the last frost is over the soil will be warm enough under the black plastic to plant.

2) Cloches. Usually made out of plastic or glass, a cloche is a hard clear covering for young transplants. You can make them out of old clear food containers just punch a hole in the bottom of the container and turn it upside down over you seedling. They don't provide a lot of protection from temperature but they do provide protection from drying winds.

3) Simple hoop houses with clear plastic covers

I don't use these . They heat up fast during the day but the insulation value (R Value) of thin plastic is not very high so they lose most of there heat at night they are good to protect some what cold hardy plants against light frosts and freezes no lower then 29*.

4) Insulated cold frame. This is the most effective option that is still relatively simple and inexpensive. There are many ways to build one including using a wood frame and glass pains but I'm going to describe the one I use which is easier to build.

The frame is made out of hoops. My hoops are mad out of bent branches but you can use anything PVC , Metal what ever. Ideally the hoops would be attached to a wooden frame using pipe fasteners but Mine is rather crude and isn't. You also need a crossbar at the top of the hoops running lengthwise. Next take poultry fencing and attach it to the hoops. this gives the whole structure some strength. Now take 4 - 6 Mil clear to white plastic and cover the whole thing. At this point it's time to make the sides. If your handy with a jig saw you can cut 4 pieces of ply wood to match the arc of the frame. If not you'll have to use plastic. Here is were it really helps to have a wooden frame. Attach one of the boards about 6" in from the end of the structure using L brackets. Then stuff the space between the board and the edge of of the frame with whatever insulation you have if you can attach fiberglass home insulation or styrofoam boards to the plywood but tree leaves will work if you have nothing else. Now attach the second board to the edge of the frame. Repeat on the other side. The rectangle of the cold frame should be oriented so that one long side faces south and the other north. On the south side cut a whole in the poultry fencing large enough for you to stick your hands in and reach all the plants. Reattach the poultry wire door with the plastic on it using wire to make hinges. now take more of the insulation and attach it to the north side of the cold frame. Then take black plastic and cover it. Finally take another sheet of the white to clear plastic and over the whole cold frame. attach it to the back (North side) of the cold frame but leave it loose on the south side. stick a twist tie in each of the corners on the south side and attach them to stakes to keep the cold frame closed. You now have an insulated cold frame good for about 15* of protection depending on its size and insulation (thew bigger it is the less protection you get.

I really hope this helps I can give you more info if you want.

daylilyfanatic, would love to see some pics :)