Most of mine are steel conduit poles, so grounded. I love them! Very easy to work with and work super well. You could use 1 irons! Lee Trevino said when lightning is around he only uses a 1 iron as not even God can hit a 1 iron.
Although I think he was struck twice by lightning. Yikes!

As a licensed electrician, if the metal tubing you are using is stuck into the ground, then your already grounded. If the tubing is embedded in a concrete footing in the ground then you are still grounded. Unless you have the tubing completely isolated from touching the earth, (nailed to the side of a building made of non conductive materials or raised off the ground with Plastic supports?) then that is the only scenario I can think of where you might want to ground it to earth. Regardless, IF your worried about a lightning strike, I doubt very much that any amount of grounding will save your plants from the intense heat and damage caused when lightning strikes it. But those are my 2 cents. Good luck.

It should be pointed out that the only time this is an issue is when the trellis adjoins, or is Jbozek mentioned; is affixed to a dwelling.
Row trellis (not affixed to a dwelling) may gain some benefit from it, but it could be argued that it is detrimental also. Either way, to my knowledge it is not required.
An exception to this would be in cases where an affixed electrical outlet was provided for grounds maintenance or frost protection etc, or if affixed electrical lighting was provided. Stand alone solar applications would not apply.

I think when they say lighting damage, they mean fire or maybe electric shock to humans? I think this is also why we are advised not to stay under the tree during lighting.

lightning damage?...yes that is the main concern here. however the concern is magnified when "lighting" is affixed for a couple of different reasons (we're talking about a trellis not affixed to a dwelling in this case). Any time an electrical circuit is involved the NEC will make a distinction to them even when not affixed because the potential for risk to the dwelling/inhabitants is still present. There is also a concern anytime a potentially grounded object is in proximity to an electrical circuit.

I sure am glad nature took all these pre cautions ahead of time. Sure glad we came along before it was too late.

This post was edited by dirtguy50 on Fri, Nov 14, 14 at 23:56

Since some author mentioned this, and I do not hear and see anything like this, I'm just curious.

Well, I figure if it is lighting outside, just stay home.

I think that wire trellises that are run between wood or plastic posts and don't go diagonally down to the ground at the ends would be the most at risk. Probably not much risk for most folks at home, as the runs are fairly short. But if you have a vineyard with long runs or the like it could be a concern. Probably more so if you live somewhere where there is a lot of lightning.

Easy enough to ground, but if you don't than you run the same risk as any long horizontal wires do (fences, antennas, etc). They can pick up charge from electrical storms (not necessarily by being struck by lightning) and potentially deliver a shock to someone/something nearby or in contact.

But if you live in an area where this is a potential danger, you likely have heard about it.

This makes sense. That book is for country home and small farm, and talking about 1+ acre.

But I've not seen this mentioned recently, even with commercial growers...

Sorta related. 52 cows killed by lightning when standing near or in contact with a fence.

Tree struck by lightning and traveled through the trees roots to a nearby metal fence.

more electrocuted cows