This may not get perfect answer. Just like to know what you folks use.
I could be sending some bare root fig and grape plants, from one, a couple to may be 5 or so. Just wonder what to use. Ziplock bag is too small for this purpose.
I presume the grapevines you would be sending are 18" or less in length? Either rooted one or two years? I would tie up the grape vines in a bundle and cut the tops back to 12"-16". Then wrap the entire bundle using a roll of saran wrap or other such plastic wrap. Put some moist paper toweling around the roots before wrapping up or put in some moist sawdust or moist peat moss around the roots before wrapping. They should ship fine. Basically the same way dormant scionwood for apples are shipped.
I’m talking about the outer plastic. Bare root plants are longer and larger than scion or cuttings. So gallon size ziplock bag is too small. I can just find an ad-hoc bag. But wonder if Amazon sells anything that is better to ship bare root plants.
Recycled grocery bags or garbage bags. Whatever you have that’s big enough. Stick it in, warp the extra plastic around the plants, double bag if needed, tie it all up with tape if needed, and box up.
U-Line products probably carries a bag that would be the size you want. They sell dozens of different size bags. I got the last of our plastic bags off of Amazon cheaper than any where else. We use them on the bare roots of our fruit trees.
I think stretch wrap would be a good option.
The kind they wrap pallets and furniture with.
Could cover roots with damp news paper / peat. And wrap them up
Stretch wrap will hold them and packaging / padding ,securely, is strong , water proof, fit any size / shape.
I’ve shipped a lot of plants over the years. Packaging is more important than most of the answers so far suggest. For example, I ship tomato plants in white boxes because I had too many incidents where the USPS left a box sitting on a porch in full sun. Brown cardboard boxes can hit 150 degrees inside in about 30 minutes. You can guess what the plants look like after 5 or 6 hours in full sun. Carefully consider how the plants you ship will be handled by the carrier and by the recipient.
You don’t necessarily have to use a bag. A carefully wrapped piece of plastic sheeting folded around so that it retains moisture works for many plants. I have used 55 gallon heavy duty garbage bags many times to transport pecan trees. You could easily cut a couple of the heavy weight plastic bags down to a size that would work to wrap trees.
More important than the bag is how the roots are prepared. Use moist sawdust, moisture gel, or even wet paper towels to keep the roots wet during shipment. If the roots dry out, the plant will die most of the time. The best prepared plants I have received were tied together with twine, packed with sawdust and moisture gel, roots wrapped with commercial plastic wrap, then placed in a shipping bag, then in a heavy duty box. Plants packed this way can be shipped just about anywhere with no problems. Each step is important so don’t skimp. Note that the roots are wrapped in such a way that they are “always” surrounded by moist media.
No experience shipping plants personally, but the nursery we purchase bare root trees from always has the roots covered in finely shredded newspaper clippings. Others use damp pine sawdust with success.