I received some very interesting advice a month or two ago,concerning
the thinning of vertical shoots for grapes trained in the Double Guyot
method.I pruned the sidehoots to one or two leaves earlier when the
canopy was in full growth,and since the beginning of August have left
more on.I removed some lower leaves just before netting a few days ago
to help ripening.
I have an excellent crop this year,which seems to be ripening well.My
mini vineyard is in Herefordshire,England,and we have to be satisfied
with Brix values maximising at about 18 for reds or whites.However one
of my reds is already at 14.0,a couple of weeks before harvest,which
will be early this year in England.Our temperatures have not been
great in the daytime at 20-22C,but the night time temperatures have
not fallen below 15C.I live about 120 miles from my vines,so have to
make a judgement when to visit.The average temperature (24hr average)
at present is about 15C,and I am wondering if anyone uses a rule of
thumb to estimate the increase in Brix/day for a given average(24hr)
temperature.

I have had a good example this year of the role of leaf area in
ripening fruit.We have a large damson tree in our garden,which
produces a good crop of sweet damsons each year.This year there has
been an enormous crop (twice or three times normal),and they have all
fallen now,but with none of them ripe.I assume that this is the same
with vines.The balance of leaf to fruit is crucial,and with a large
crop,it is important to maintain a maximum leaf area,consistent with
keeping protection against powdery mildew-good air flow and spray
coverage.

I have also for the first time put on a three inch layer of garden
compost around each vine in the early spring period.I had not done
this previously,since I thought the vines were vigorous enough in our
cool climate.However,although the vigour has increased somewhat
further,the vines look incredibly healthy,with little powdery mildew,
and I had a very good flower set.I think the compost keeps the soil
more moist,thus avoiding a major powdery mildew attack in very dry
spells.

Michael