Prune a grapevine after blooming

Grape vines should only be pruned when in the dormant, over-wintering stage, that is leafless.
Once the sap starts to run in spring any fresh cuts will weep sap and could kill the plant.

The sap running thing is often a little overstated. I always trim back any growth which extends beyond the top wire of our Guyot trained grape vines, as well as other growth not neccesary to ripening. I do it several times throughout the growing season, and never get any sap leakage and have yet to see any signs that the vines suffer as a result.

Commercial vineyards appear to do a fair bit of trimming too. Grape vines trained in the restricted forms of commercial vineyards put on a huge amount of growth throughout the Spring/Summer. If they were not pruned there would be a huge amount of unruly growth, not the neat rows you see in a well tended vineyard.

Mark

Thank you both for your interest. I will give my runners a minor prune after the fruit has set. It is my hope that the vigor of growth will go towards the fruit, not runners. I will try for a shape to fit my arbor, which must remain small due to deer and squirrels voracious feedings!
Again, thank you. Jim

I always prune the growing shoots when the fruit has set (about 2 leaves after the final fruit trus), I have found that you get better fruit when this is don as the plants energy goes into the fruit rather than the shoots.
And if you are into wine making then you can use the prunings to make some excellent wine.

LittleMark's comments about pruning need to be treated with a little care as he doesn't differentiate between hard wood and soft wood.

Yes softwood (this year's growth) pruning / pinching out / trimming back can be undertaken as you wish without any bleeding. BUT try and do that with the hard wood from previous years' growth and you will have a problem. That must not be cut except in the depth of winter when there is no sap running.

My father did it once - he was no gardener and my mother let him loose repairing the greenhouse once - and in the end he did manage to stop the flow with a hose clip tightened very tight.

The small greenhouse vine usually consists of main stem trained along the GH roof (4 to 5 years of growth). One side branch should be allowed to develop every 9" along the horizontal part of this stem - none on the vertical. Any additional ones should be removed as they start to grow, but check that there are going to be flowers on the retained one before removing all the extra ones. In an 8 ft long GH this should give you up to a dozen side branches.

Allow these side branches to grow to around 20" and train (carefully to avoid breaking the soft growth) to a wire stretched 6" below the GH roof. Any side branches without flower clusters should be removed. In a mature vine you can allow two clusters per branch - in a younger vine I would limit this to one.

Keep pinching out all extra side growths from the main stem and the side branches.

When in flower, run your hand gently down each cluster to spread the pollen.

I spray against mould about a month after fruit set fortnightly 3 times.

Just then enjoy the fruit.

In the depth of winter, cut back all the year's growth to 3" or so from the main stem. The idea is to get sufficient growth buds for the following year, but you will find in time that buds will appear pretty well regardless of how far you cut back on a mature vine.

And then you start all over again.

Rob

I prune back any new growth whilst grapes are forming to channel energy into the grapes.

Mr T chopped back some of our vines this spring - the things dripped like a tap for days.

Still haven't worked out how to get any grapes though.....................