do all squash need trellising?

[Doug9345]

A wooden trellis would be being used; would it be strong enough to bare the weight of fruit? This is total weight of fruit per plant.

This would depend on how the trellis is built. If it is built out of lath, most likely not, but if it was built out of heavier material, yes. Your house is wood and will stand hurricane level winds.

If squash plant is positioned w/trellis correctly do you still have to train the vines, or will it climb up the trellis itself? If you need to train vines, how?

As far as I know squash won't climb like grapes do. You basically tie them to the frame work or get them to weave through the framework.

Was told you need to anchor trellis to support it; there are no trees, fences, etc. to attach the trellis to as support.
Could I anchor trellis legs into soil; will be using soil mix which is more loose than regular dirt. Will I still be able to anchor legs into soil? If trellis is anchored into soil, how deep?

Ropes to something like tent stakes in the ground or braces against stakes in the ground would work. The problem isn't just the weight of the plant and fruit, but wind. A large trellis with a squash plant on it has a large sail area. Loose soil makes it worst. I'd get the trellis as deep as I could.

Was told to tie vines to trellis; is this just the vines that have fruit?

I think you'll have to tie all the vines to the trellis because they won't naturally attach themselves.

[Keiththibodeaux]

I have never trellised my squash and still made more than we could eat. It is a very prolific crop.

[dustdevil]

Some people use mesh bags(like the ones oranges come in) to tie melons up to a trellis and give them support.