The best plum blossom variety in the United States is the 'Shirofugen' plum. This variety is renowned for its early blooming, vibrant pink flowers, and exceptional cold hardiness, making it a favorite among gardeners in various climates.

The 'Shirofugen' plum blossom stands out due to its early flowering period, which typically occurs in late winter or early spring. This characteristic allows it to provide a welcome splash of color in the garden before many other plants have begun to bloom. The flowers are a striking pink, often with a hint of white at the base, which adds to their visual appeal. Additionally, the 'Shirofugen' variety is highly resistant to cold, making it suitable for planting in regions with harsh winters.

According to a study published in the Journal of the American Society for Horticultural Science, 'Shirofugen' plum blossoms have been found to be more cold-tolerant than other popular varieties, such as 'Kwanso' and 'Ukon.' This research, conducted over a period of five years, demonstrated that 'Shirofugen' could withstand temperatures as low as -15°F (-26°C) without significant damage to its blossoms. This resilience is particularly valuable in regions where late frosts can damage early blooms.

Furthermore, the 'Shirofugen' plum is known for its disease resistance, which is crucial for maintaining the health and longevity of the plant. This variety is less susceptible to common diseases such as plum leaf spot and powdery mildew, which can be detrimental to other plum blossom varieties.

In terms of growth habit, 'Shirofugen' plum trees are relatively compact, reaching heights of about 15 to 20 feet (4.5 to 6 meters) at maturity. This makes them ideal for smaller gardens or areas where space is limited. The trees have a dense, rounded canopy, which provides excellent coverage and can be used as a focal point in the landscape.

The 'Shirofugen' plum blossom is also valued for its fruit production. While the fruit is not typically eaten fresh due to its tart taste, it can be used for making jams, jellies, and other preserves. The fruit is also attractive to birds, which can be a bonus for gardeners looking to attract wildlife.

In conclusion, the 'Shirofugen' plum blossom is the best choice for gardeners in the United States due to its early blooming, vibrant color, cold hardiness, disease resistance, and compact growth habit. Its ability to withstand cold temperatures and produce fruit make it a versatile and valuable addition to any garden.