I did an experiment with some weeping willow to see about weaving green. It wove so beautifully. I was in heaven with nice long weavers. I also harvested some red osier for some color at the top.
I tightened it up as it was drying...but still it became loose and very open. So, listen to the books. They are right about weaving green. The material shrinks as drying and your basket will be floppy and want to come apart. This basket is still totally usable, if needed in a tight situation, you could weave green for an immediate need. But for a nice tight basket that will last, dry your material first. Then soak it when ready to use. Happy weaving!