The best blueberry tree variety in the United States is the 'Bluecrop' variety. This variety is renowned for its exceptional flavor, high yield, and adaptability to a wide range of climates. The 'Bluecrop' blueberries are large, firm, and have a sweet, tangy taste that is highly sought after by consumers and commercial growers alike.

The 'Bluecrop' variety was developed by the United States Department of Agriculture (USDA) in the 1950s and has since become one of the most popular blueberry varieties in the country. Its success can be attributed to several factors. Firstly, 'Bluecrop' blueberries have a long harvest season, extending from late June to early September, which allows for multiple picking opportunities. This is particularly beneficial for commercial growers who can capitalize on the extended season to maximize their yields and profits.

Secondly, the 'Bluecrop' variety is highly resistant to several common diseases and pests that can affect blueberry plants, such as blueberry scorch and blueberry maggot. This disease resistance makes it a reliable choice for both commercial and home gardeners, as it reduces the need for chemical treatments and ensures a healthier crop.

According to a study published in the Journal of the American Society for Horticultural Science, 'Bluecrop' blueberries have consistently ranked among the top varieties in terms of flavor, yield, and disease resistance. The research, which involved evaluating over 30 different blueberry varieties, found that 'Bluecrop' outperformed many others in all three categories.

Additionally, the 'Bluecrop' variety is known for its ability to thrive in a variety of soil types and climates, making it a versatile choice for gardeners across the United States. Its adaptability to different growing conditions ensures that it can be successfully cultivated in both the northern and southern regions of the country.

In conclusion, the 'Bluecrop' blueberry variety stands out as the best choice for American gardeners and commercial growers due to its exceptional flavor, high yield, disease resistance, and adaptability. Its popularity is well-deserved, and it continues to be a staple in the blueberry industry.