Apple trees are generally small trees, and a given variety can be grafted onto dwarfing or semi-dwarfing rootstocks for smaller and less vigorous plants. If left untrimmed, a tree grown with standard (seedling) rootstock will often reach a height of 9 metres (30 feet) with an equally large crown diametre. The bark is usually brown and scaly. The simple leaves are roughly oval in shape and usually have fine teeth along the margins. Apple flowers are showy with five white petals, often tinged with pink, and numerous stamens. The flowers are pollinated by bees and other insects, and most varieties require cross-pollination for fertilization.

How is the ripeness of an apple determined?1 of 2
How is the ripeness of an apple determined?Learn what creates the signature taste and smell of one of the world's favorite fruits—the apple.
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applesBaskets of red, yellow, and green apples.
The apple itself is a pome (fleshy) fruit, in which the ripened ovary and surrounding tissue both become fleshy and edible. When harvested, apples are usually roundish, 5–10 cm (2–4 inches) in diameter, and some shade of red, green, or yellow in colour; they vary in size, shape, and acidity depending on the variety, of which there are thousands. Apple varieties fall into three broad classes: (1) cider varieties, (2) cooking varieties, and (3) dessert varieties, which differ widely but tend to emphasize colour, size, aroma, smoothness, and perhaps crispness and tang. Many varieties are relatively high in sugar, only mildly acidic, and very low in tannin. In the United States, popular dessert varieties include the Honeycrisp, Red Delicious, Gala, Granny Smith, and Golden Delicious. Apple varieties that ripen during late summer are generally of poor quality for storage, while those that ripen in late autumn may be stored for as long as one year. For long holding, temperatures only slightly above the freezing point of the fruit are generally desirable. Apples may also be stored in inert gases or in