Black Hamburg grapevine in greenhouse- How many bunches should I allow to mature?

Hi All, thanks for welcoming me aboard.
I'm seeking advice upon the above please but feel I should first give some reason for the question. The vine has taken well and is now in it's sixth year. In 2018, it's first year of cropping, it had a super crop of 30 bunches harvested in early November resulting in three gallons of wine! By contrast last year was a disaster as mildew began appearing on the fruit early on which I couldn't contain in spite of a regular spraying programme. I removed the entire crop in late July in the hope of giving it a rest and therefore a better crop this year! The roof was taken off the greenhouse(10ft x 6ft) for over wintering and the vine well mulched and fed. I replaced the roof, closed the door and replaced all glass panes in early March. Since then it has had fresh growth from all the spurs with at least 2 embryo bunches upon each cane. So, how many dare I allow to mature? One on each would return thirty, but dare I risk more?

 

I don't think more than one bunch per spur, but then I don't know how close to gether the spurs are or how long the vine is.
Mildew is a problem that is to do with growing conditions rather than over cropping.
Is the root inside green house?
If so I can only think you need to water more.

 

Hi Pete, thanks for response. There are two main arms with 12 spurs upon each over the 10 ft run so each are about 10" apart. The root is within the greenhouse, central at one end with 4" dia pipe adjacent to it outside going down approx 18" this is where I water and feed it from. Naturally can increase the frequency of watering if needs be. Perhaps a couple of times a week in the past. Once the chance of frosts are gone I leave it well ventilated by leaving the door open and removing a couple of panes of glass at the opposite end as well. There are three window openers, two panels in the roof on one side and a louvred one opposing the door. Hope the three photo's attached assist!

 

Sounds good Adrian, just keep up the watering, as you are going for wine I'm guessing you're not that bothered about the size of the individual grapes.

 

Or the Pips I've got a Back Hamburg in the greenhouse, lovely flavour grapes, but it would be nice not to have to keep spitting-out ...

 

I ripped my Black hamburg out last winter , couldn't cope with all the pips . I've got lakemont now. I only let one bunch per stem

 

Which Is why I'm trying "Flame" and "lakemont" outside, still waiting for a good crop.

 

Thanks for all advice to date the grapes have progressed superbly since and nearing full size. Don't know if I can test your patiences further, but as the Greenhouse roof is now decorated with vine leaves there's precious space anywhere for the sun to shine on the grapes. My understanding is that the leaves help to ripen/sweeten the grapes as does the sun so :- Should I leave all leaves in place or remove a few to let the sun shine through. Any thoughts?

 

Might I point out, Black Hamburg is NOT a greenhouse plant. It should be grown outside.

 

Well, that's mighty interesting but hope you won't mind if I don't tell that to mine. But guess if it does eventually find out I'll just have to remove all the panes of glass.

 

Think I might remove some of the leaves but I don't think the fruits need direct sunlight to ripen.
Removing leaves would help with ventilation though .
The fruit might look pretty much full grown but I think the ripening process takes quite a while really.

 

Many thanks for the advice Pete. As you suggest will take out a few from dudicious spots to allow some more light and air through. Yes, it seems to take a long time before veraison begins. A little like waiting for the kettle to boil perhaps.
Nice to receive a positive response. I wonder what the previous poster based his conclusion upon!

 

Well we all have our opinions, I know people who have grown Black Hamburg in or out, it does ripen ok outside most years I think.
But greenhouse means you can control things a bit better and obviously location makes a difference, although I'm sure it would be ok outside in Suffolk.

I think Monty Donn of gardeners world fame grows his in a greenhouse.

 

Indeed Pete, or even this one! Obviously nobody told the original vine that it shouldn't be grown under glass.

The Great Vine

 

He based it on over 40 years experience as an amateur AND professional gardener/horticulturist.