And what is the significance of the fact that the seven good ears of grain grew on one stalk?
Ramban: It was a sign that the seven years of plenty would be consecutive.
Rashbam: It was a sign of the extent of the bounty, inasmuch as that, for every grain that was planted, seven stalks grew.
Moshav Zekenim: The good years will be equally good. The bad ears did not grow on one stalk, for one was worse than the previous.
Why does the Torah repeat the dreams three times (when he dreamed, when he told Yosef, and when Yosef interpreted them)?
Moshav Zekenim (16): The three mentions of seven bad cows and seven bad ears 1 allude to 42 years of famine for Mitzrayim. There were two before Yakov came, 2 and the other 40 were "paid" through exile.
How can we count both cows and ears? It was repeated to show that it will happen soon! Since it changed from cows to ears, we count both (Moshav Zekenim). This is unlike those who explain why he needed to dream about both of them - refer to 41:2:1:2. (PF)
Hadar Zekenim (27): Yosef said "Yihyu Sheva Shenei Ra'av." This was a Tefilah that they only be seven. Yakov prayed that they be only two.
רש"י: טודי"ל בלע"ז: מה בא רש"י ללמדינו?
גור אריה: בדרך כלל 'קנה' מתייחס לקנה הגדל באגם, ולכן הביא רש"י דוגמה מלע"ז שגבעול של תבואה גם נקרא 'קנה'.
רש"י: שייני"ש בלע"ז: מה בא רש"י ללמדינו?
גור אריה: 'בריא' בדרך כלל מתייחס למי שאינו חולה, ולכן הביא רש"י דוגמא מלע"ז שניתן לומר 'בריא' על בשר טוב.