My wife has a few 'plastic' pots that she uses for herbs, and places on the deck outside our kitchen. My biggest use of them is in starting the seeds each year. I used peat pots for many years, and was always annoyed at the amount of failures, and resulting re-plants. I have found a better way, especially for my tomatoes and peppers. I use these bio-sponges to germinate the seeds, and then when they have about 2 or 3 leaves, I move them into small plastic pots(square) that are almost 4 inches deep, and 3 1/2 inches square. (with potting soil filler) They have consistently done much better than the peat pots ever did. Some suggests that the peat absorbs too much moisture, maybe. When it comes to planting in the garden, they pop out of the plastic pots quite easily, with their roots well developed and holding it all together. This year, I tried using these foam shipping trays for wine bottles. I buy a case of wine, now and then, and when they are shippped, they come in foam formed containers for the bottles. I realized they are not too wide, but nice and deep, so thought I should try them for my seedlings. I lined each cylinder shape with wax paper, then put in the plant which grew in the biosponge, with the soil filler. I'll be putting them in the ground later this week, so will be anxious to see if they pop out easy enough with the wax paper. They also grew very well from the seedling stage. We'll see!

It is generally not recommended to put plastic sheets directly over trees for attempted frost protection. Any place the plastic touches the leaf will result in conductive heat loss and thus no frost protection. And, if the plastic is left on the tree in sunny days, even 50 deg., the tree will suffer heat damage. There is a permeable plastic product, actually polypropylene, being sold by frostproof.com for use on trees. The product may give a few degrees of protection, but on very cold nights, less than 28 deg., it may not help much. It also must be removed on each sunny day.

I'm using the empty water bottles themselves, cutting them in half then pushing the top half over the bottom half like you would with a 2L bottle so you don't have to worry about plastic or taping. So far they're tucked into the patio containers (which I haven't cleared out yet) or lined up in a clementine box. Others are using green 2L (like from mountain dew or ginger ale) so colored plastic doesn't sound like a problem.

Not sure about Cauliflower or Beets... Peas are cool season; can be put out early. I had mine out in April (both direct and wintersown) and frost wasn't a problem. They were finished up by mid June. Broccoli went out early too and finished by mid July. Found this broccoli production guide; you could use it as a guide maybe? Here is a link that might be useful: NC State U...Broccoli