Unfortunately, the data as to ripening time given by originators
and introducers of varieties are not always reliable. This
untrustworthiness of data is readily accounted for in several ways:
First, growers do not generally agree as to when grapes are ripe nor
as to how long they are fit to eat. Again, much confusion as to when
varieties ripen and how long they will keep arises from the fact that
grapes ripen at different times in different places, and it is
difficult for the grape-grower in Maine to make allowance in season
for varieties, the time of ripening of which is given for Maryland.
There are also other causes than the seasonal differences in grape
regions for variability in ripening time; thus, some soils are warmer
and quicker than others, and on these grapes ripen earlier.
Application of nitrogenous fertilizers may delay the period of
ripening somewhat. Grapes ripen perceptibly earlier on old plants than
on young ones. Lastly, every vineyard in a particular region has its
own particular climate caused by the lay of land, nearness to water,
air currents and altitude which cause small differences in ripening.

The following table taken from Bulletin No. 408 of the New York
Agricultural Experiment Station gives the ripening dates of grapes at
Geneva, New York. It is necessary that the reader know something about
the conditions affecting the ripening time at Geneva. The latitude is
42 deg. 50' 46". The altitude is 525 feet above sea level. The vineyard
lies a mile west of a relatively large body of water. The soil is a
cold heavy clay which must delay ripening time somewhat. The land is
level. The data are given as an average for three seasons, 1913-1915.

The figures given for "weeks in common storage" cover a variable
number of years, but for all varieties three or more years. The
grapes, after being picked, were at once placed in common storage in a
room on the second floor of a building. There conditions were not
ideal, and no doubt the season of storage would have been prolonged
somewhat had the fruit been kept in a better storage-room.

TABLE V.--SHOWING THE RIPENING TIME OF GRAPES

=====================================================================
| WEEKS IN | | | | |
| COMMON | VERY | | MID- | | VERY
| STORAGE | EARLY | EARLY | SEASON | LATE | LATE
-------------------+----------+-------+--