For the next 'Dack Hack (Adirondack flower farming hack) here is a quick tip. I can't claim it to be my own. I spotted it on Instagram last year-- I think in a photo from a large scale sweet pea growing operation. Last year, we struggled with tying up the sweet pea vines. Our method was messy-- once and a while we used lengths of bailing twine to coral the vines up and attach them to the trellis.
This season, we're trying to prune more of our vines regularly and train the plants to put more energy into fewer, larger flowers - hopefully with longer stems, too. We don't know yet how successful it will be, but we'll keep you posted.
To attach the vines to the trellis and keep them a bit more organized (that is kind of crazy to say if you have seen or worked with sweet peas - but it's the goal) we are using plastic clothes pins.
Clothes pins are easy to re-use and remove from lower sections of the vines as the vines attach themselves. The plastic won't rot or hold moisture against the plant, and the metal springs are designed not to rust. What's also great is how they are designed. The "pinching" part attaches easily to trellis netting. The larger hole through the clip allows a vine to slip up and down a little as it grows or when a breeze passes by.
It is a little funny to see all the clips attached to the trellis, but they seem to be working. And, I suppose that they can be removed for photos down the road if we decide we don't like the look of them.