I am growing seedless table grapes in zone 4b/a.
My plants are in 50 foot rows planted 8 feet apart, 5 plants per row. The trellis is a Geneva double curtain (2 parallel wires, 4 feet apart @ 6 feet from the ground). Rows run North – South.
Due to the cold I am growing multiple trunks to have backups in case of winter kill.
I have the following questions:
Is there a benefit to having a fewer number of trunks in that energy more easily reaches roots? Eg. 2 trunks with 1 or 2 canes each vs 4 trunks with 1 cane each.
Is it better to have fewer long canes or more shorter canes? Eg. 2 trunks with 1 cane each (2 canes total 8 feet long each) or 4 trunks with 1 cane each (4 canes total 4 feet long each)? Total cane length of each (mature) plant = 16 feet of canes.
General advice seems to be to trim trunk at top wire and in next year grow a cane from trunk along top wire and then either cane or spur prune. Right now my trunk has grown up to top wire AND 8 feet along the top wire. Why can’t I just leave the whole thing as one long trunk as opposed to trimming and growing a cane to replace the potion of trunk I cut off. The way I understand is that thick, extremely vigorous first year growth can be less hardy and even less productive. What would you do?
I am going to experiment with different growing options and cane vs spur pruning. Given that I have multiple trunks I will probably try both cane and spur pruning for each plant as well as laying down the trunk vs leaving trunk exposed during winter.
Now onto my training questions. I have several options. As metioned it is a Geneva double curtain running north-south with a east wire and a west wire. So to summarize.
Option A) 1 trunk growing up to east wire and growing cane 8 feet north with other trunk growing up to east wire and growing cane 8 feet south. I would alternate plants, eg the next plant in the row will grow on the west wire.
Option B) 1 trunk growing up to east wire and growing cane 4 feet north with 2nd trunk growing up to east wire and growing cane 4 feet south. 3rd trunk growing up to west wire and growing cane 4 feet north with 4th trunk growing up to west wire and growing cane 4 feet south.
Option C) 1 trunk growing up to east wire with 4 foot canes growing north AND south. 1 trunk growing up to west wire with 4 foot canes growing north AND south.
What do you think? For now I am leaning towards the 4 trunk option B as I am still not sure of the majority of these grapes hardiness in my zone and I will view it as insurance. Plus I can experiment leaving 2 trunks exposed all winter (1 cane pruned, 1 spur pruned) and I can bury 2 trunks (1 cane pruned, 1 spur pruned) and see what each plant likes.
I think more trunks is better in a climate that cold. Shorter canes is also probably better. In actual practice cover the trellis with the best live wood each spring. You aren’t going to have ideal canes just where you want them. So you won’t have all those choices each spring.
Biggest factor will be cane survival. If the canes are undamaged all options will perform well. If canes/buds are half dead none will look good.
Thanks. I appreciate that. I don’t know of anyone around me growing table grapes and for sure no one is doing it on a Geneva double curtain (for those interested I got my arms from www.agritek.com/wolverine_grape - UPS to Canada was brutal though). My 4mm monofilament and irrigation supplies from www.duboisag.com/.
I am still having a hard time with vine terminology but here is what I have decided to do so far. Some of my grapes that have been in the ground for 2 years have this year pushed up shoots from the base that are now 14 feet long (6 feet up to trellis wire and another 8 feet along the wire). Some of these have also put out side canes that are now reaching 3-4 feet long.
Those that are 14 feet long and not impinging on neighbors will be left (ideally 1 left up on trellis and other I will take down and bury to compare hardiness).
Those that have 3-4 foot long side canes coming off near the trellis wire will have the trunk cut at that level and that cane become the new cordon on the trellis.
Those that have the trunk just reaching the top wire will have a heading cut at that level and a new shoot trained up to trained along the wire to be the new cordon/cane.
In all cases I will be pruning similar to what is shown here starting at min 23 (https://www.youtube.com/watch?v=PZbePV9nw-0). For grape beginners I recommend this whole series of videos by this guy. There are 38 videos so it will take a while to get through them.
For first year of fruit I will limit myself to about 30 buds total for the vine (on my big vines that put out 4 trunks + 8’x4 canes along wire I will be more generous with say 50 buds. Given my climate and frequent late frosts (this year was May 23 when we got to -3 celcius) I will prune fruiting canes to 5 buds in very late winter and then at the time of terminal bud swelling will cut back to 2 buds to delay shoot growth.
I think that’s a good plan. Limiting fruit load will increase hardiness and improve berry quality. What I like about grapes is it’s easy to change pruning and training as we learn. No mistake is permanent. Good luck!!
To update, the 4 trunk system is definitely the way to go in my climate and with my soil. Some varities had 2 or 3 trunks die back. Others had 50% of the trunks have fruit bud death. BUT this means I still have 1 or more trunks that survived to produce fruit! I am now growing my plants with 4 principle trunks and then allowing 2 renewal trunks to shoot up as well. I lay down all trunks in the fall and then in the spring will wait to see what trunks have survived then if all 4 primary trunks survived I will cut back 1 and replace it with a renewal trunk. This means no trunk will ever be more than 4 years old so they will still be flexible enough to lay down each fall. The 2nd secondary trunk will be available if dieback was worse and I lost other trunks.
Good to know, I am always wondering how many trunks to keep going. I never thought of cutting one of them back and replacing it, I will have to do that next spring.
I have to mulch my grapes to keep them alive thru the winter. Last year I decided to roll them up like a wreath, lay it down and pin it to the ground with landscape pins. It worked really well and made it easier to mulch the wreath instead of having to mulch along the whole length of vine.