How do I use this trellis for Cab & Merlot?

[Snafflebit]

I am taking over the management of a backyard vineyard with 26 vines located in Almaden Valley of San Jose CA. The owners do not know which vines are cab and merlot. I will need to identify that.

the trellis style was hard to identify but I think it is called a wye or double cross arm. The vines are planted 6’ spacing and are divided into 4 cordons. So I assume this will by managed like a TWC with a divided canopy. My question is why are there four wires on the top cross arm and what is the use of the inside two wires?

since this is a 4 cordon system this will of course double the number of buds. The cordons are spur pruned and typically 3’ long. So I calculate 9 spurs each of 4 cordons and 2 buds per spur is 72 buds which may be overcropping the vines. Would it be advisable to put vines at 3’ spacing and shorten the cordons?

Also 8 vines are dead. I looked at a cross section of a cordon and did not see streaking of the wood to indicate infection. The cordons are wrapped around the trellis wires and may be girdling but I do not know. Would it be worthwhile to attempt grafting replacements or simply buy new vines? I have no experience selecting grape rootstock. I have not grafted grapes, I have attempted citrus with limited success.

 

[Xnke]

I would use that trellis in that configuration as a Lyre style, basically just use the principles behind VSP with a divided canopy.

You could also use it as the Wye style, by letting the shoots grow up and arc over the top wire to the outside, which is what it appears has been done. Think mid-wire cordon with a top catch wire, because that's how it's been done in the past.

Cut all the vines back in the style of the dead ones, but I would leave between 30 and 40 buds, not 72. Others surely will have more informed thoughts on this-especially some of the members from California!

 

[Snafflebit]

I found this article by Lodi Growers that addresses using wye trellis for cab and merlot and quad cordon. I hit the jackpot. They suggest single bud spur pruning. It seems risky but I have seen it done around here.

https://www.lodigrowers.com/vine-growth-capacity-and-horizontally-divided-vines/