I thought that I would try again to further my understanding of
observations on my vines in England this year,based on the very useful
replies and discussion.There will always be disagreement,but as
someone new to growing grapevines,I hope that I can understand the
issues.I apologise to doubi..for my recent comment,and hope that he
can continue to help.
Let me try again to summarise my recently gained knowledge:
1)Using wood chip as a mulch on the surface around the vine can
greatly help in the stabilisation of upper soil moisture content,and
will not affect the nitrogen of the vines-rotovating or digging in
wood chip will rob the soil,and this is my gardening experience.Garden
compost could be even better,as it introduces a living worm population
which may help soil texture.
2)Wasps or other insects are not the source of primary damage to
ripening grapes,but can spread the rot to other grapes in the bunch.A
primary source of damage could be a heavy rain shower,causing
splitting,followed by wasps,etc moving in.I think that this is what
happens with plums after they split when nearing ripeness.My culling
of the majority of the wasp population will still help,I believe.
3)I thought that darker vine leaves to be an indicator of too much
nitrogen.I would like to know what the indicators are for vines
needing more phosphates,or potash,so that I know what fertiliser to
add to my compost.
4)One indisputable fact is that my vines and grapes are sofar much
healthier this year. I believe that probably the main cause is the
long very warm dry spell here in June-but I do not really know.It
could be the compost keeping moisture levels stable.
5)My original post was about pruning of laterals or sideshoots for
vigorous vines in a cool climate.My policy now is to remove most of
them in June and July to prevent a dense canopy developing,thus
encouraging powdery mildew,and then leave them alone after veraison to
have maximum leaf for the ripening period.
I hope that my understanding is improving and welcome your comments
The following link provides pictures of grape leaves with various
nutrient deficiencies. Potash (potassium) and magnesium are the most
common. Magnesium can be easily supplied with a few spoonfuls of
Epsom salts. I read the other day that grapes usually don't need
You hit the nail on the head about the benefit of mulch. If you had a
long warm, dry spell and your vines remained healthy, it was due to
the stable moisture levels enabled by your mulch.
Thanks for that,Stephen.I have two questions.
1)When my grapes are ripening,the lower leaves seem to die back
naturally.Is this the time to look for mineral deficiencies
e.g.potash,or at an earlier stage?
2)What are the symptoms of nitrogen deficiency or excess?
The lower leaves dying back during ripening is a natural occurrence.
these are the first leaves to open during the season. Leaves reach maturity
and are no longer contributing after about 60 to 90 days. It is the young
leaves at the top of the vine that are contributing to photosynthesis and
At this time of the year, the old leaf die back is natural. If it
occurs prior to veraison, it can be a sign of drought stress (which
can be lessened by the use of mulch). Drought stress may be manifest
by signs of nutrient deficiencies. If you get yellow/red/purple
streaks in your leaves prior to ripening time, it is nutrient
deficiencies showing up like in the pictures on the link.
Nitrogen needs are variety dependent to a degree. I have seen Merlot
described as a "nitrogen hog", meaning if it has a lot of available
nitrogen it will grow like crazy and not produce many grapes. If a
vine has rampant growth but little fruit production, it probably has
too much nitrogen. If it is a weak grower with small pale leaves, it
may benefit from a little extra nitrogen and other nutrients.
Although I do not live in a semi-arid part of the world,my
sloping dry limestone south facing soil does dry extremely quickly
during the summer.The grass on the adjoining orchard becomes a pale
straw colour for a couple of months,and the planting of fruit trees in
the orchard is almost impossible without regular watering in the first
couple of years.So it may be the case that mulching in March helped
the vines over the very warm dry June period,and stopped any powdery
mildew developing.In other years,I have some powdery mildew,even
though I spray regularly with wettable sulphur.This year I have not
detected any powdery mildew on any of my four varieties of
vines.So,maybe the jury is still out as to whether the mulching has
helped the vines in my particular situation,but I am tempted to mulch
again next year.
It's well documented that fungus preys on unhealthy plants. Plants
that are stressed or made to suffer. Sound familiar? Also the
mychorrrizal fungus in the mulch is helping the roots and vine. On the
lateral issue, As I said before, laterals are produced by the vine
after bloom to help with ripening. Depending on when bloom is is when
you should stop pruning laterals. I wouldn't base my lateral pruning
based on a date but on the date of bloom. The vine will most likely
not produce laterals until after bloom and the most important set of
laterals are the ones closest to the base of the shoot ( closest to
If you had a sunnier and warmer season than usual thus far, that could be
the major reason for lack of powdery.
How many rows do you have?
Could you do an experiment and mulch some and don't mulch others and see if
there is a difference?
"Could you do an experiment and mulch some and don't mulch others and
there is a difference?"
I already did that. There is a big difference in the mulched vines
compared to the unmulched vines. Micheal is just confirming what I and
shbailey have seen. Why don't YOU do the experiment? You seem to be a
typical viticulturalist, a stubborn dinosaur regurgitating old myths.
My response was to Michael - NOT you.
I don't need to. My vines are healthy and there is no issue with lack of
moisture where I live.
WHY don't you answer my questions?
Where do you live. What varieties are you growing and how many vines do you
have? Have you ever worked at a commercial vineyard?
Hardy har har. I am a Geologist but putting me in the realm of dinosaurs is
stretching it a might.