I bought some plant tee-pee things that hold water and surround each plant, making a little greenhouse. They are a color variation on the Wall of Water product that I've seen in many gardens for years.

This is from the packaging:
"Position the Kozy Coat in your garden over your plant. Adjust the Kozy Coat into a teepee shape by making the bottom as wide as possible and gently squeeze the top together. If the garden soil is still cold (or even frozen!), place your Kozy Coats on the soil for a week to 10 days. When the ground has been warmed, remove the Kozy Coat and set your plant in the ground. Re-position the Kozy Coat over your plant.
When the weather is reliably warm (mid to late June), remove the Kozy Coat and store for use next season. Some gardeners in regions with moderate climate prefer to leave Kozy Coats on all summer. Peppers and Eggplants are heat-loving plants that will do better throughout the summer with a Kozy Coat.
The earlier you plant, the earlier you'll be picking. You don't have to worry about the heavy frost or late blizzards. Kozy Coats will protect your plants through the worst spring weather. Even if the water in the Kozy Coat turns to ice, your plant is still protected. (emphasis added) The Kozy Coat becomes an igloo, keeping in heat and warmth from the soil around your plants."
As you can see, the color is red, and that is supposed to make tomatoes want to grow fast and big and wonderful. We'll see. The gardening catalogs are also selling red plastic to put on the ground around your tomato plants as mulch.

I don't have much hope for cucumbers, and unless they do well, I won't try them again. Tomatoes and zucchini are what I aspire to master this year.
A couple of years ago, our friend Jondude told me that rhubarb plants do well when planted next to a sidewalk because of lime leaching from the cement into the soil. I have thought about this, and have finally figured out a spot to try it, where there might be enough sun and out of the way of the lawn mower. I'll buy a new plant to try it out.
There was a plant on the riverbank that might have been wild or my mother planted it 25 years ago when the trees there were tiny and it would get sun. By the time I got to it, it was shaded all the time, so never prospered. We moved it to a flower bed in front of the smaller rental cabin, but it hasn't taken off. I'm not going to move it again, I'll give it more attention and see if that helps.
This is not it:

As you know, the leaves of rhubarb are poisonous, but the stalks are very tasty. I've always have wondered how early pioneers figured this out - did they sacrifice a child, or maybe it was enough to see the cow die after eating the leaves.