Answer: Those "caps" are used to protect young spring transplants from the cold, but would not be particularly helpful to your plants, especially in the heat of summer.
Options to protect your veggies include making a small wind fences out of weed barrier groundcloth or floating row cover material attached to stakes. These wind blocks, oriented across the prevailing winds, should give protection downwind for about 2 1/2 times the height of the barrier. A porous "wall" to block the wind is better than a solid wall as the latter tend to create turbulence whipping downward over the top of the barrier. These fabrics are available from local nurseries and mailorder from: Mellingers; 2310 W. South Range Rd.; North Lima, Ohio 44452-9731; 1-800-321-7444.
Another option would be to plant a living barrier, such as a vine on a section of fencewire to protect from the wind. Some gardeners alternate a few rows of corn every so often with other veggies to act as a windbreak. Just make sure the windblocks are not shading the other veggies too much. Good luck with your garden.
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