The acorn is considered to be egg-shaped, but, I think that is debatable. It is 5/8 inch to 1-1/8 inch long. It has a cap that is reddish-brown. The cap has tightly over lapping scales.
This paper discusses acorn development which is rather interesting when realizing if one is going to cut down trees, there needs to be acorns to grow new trees. This is everything you wanted to know about acorn development but were afraid to ask.
Northern red oak begins flowering at approximately age 25 (click here) but doesn’t reach maximum flower production until age 50 - 200 years. Flowers are incomplete and imperfect. Incomplete flowers lack one or more of the four basic floral parts such as petals, sepals, carpels and stamens (Raven et al. 1992). An imperfect flower contains only stamens or carpels but not both. Each oak flower contains either male or female structures. Northern red oak is monoecious (Sander 1990, Raven et al. 1992) which means that both the staminate (male) and pistillate (female) flowers occur upon the same tree. Cecich (1992) reported research by Irgens-Moller (1955) that the genus Quercus is capable of self fertilizing, but that Jovanovic et al. (1971) could not reproduce the same results....
