The best variety of winter jasmine for American gardens is 'Jasminum nudiflorum 'Sundance'.' This variety stands out due to its vibrant yellow flowers that bloom in early winter, providing a stark contrast to the cold, gray landscape. The 'Sundance' variety is also known for its more compact growth habit, making it suitable for smaller spaces or as a hedge.

The reasons for choosing 'Jasminum nudiflorum 'Sundance' are multifaceted. Firstly, its early blooming period is highly sought after, as it can offer a burst of color during a time when many other plants are dormant. According to a study published in the Journal of the American Society for Horticultural Science, winter jasmine varieties that bloom early are more likely to attract pollinators and contribute to local biodiversity. Secondly, 'Sundance' has a more controlled growth pattern, which is beneficial for gardeners looking to maintain a neat and tidy appearance. This controlled growth is also advantageous in areas with limited space or where pruning is not desired. Lastly, 'Sundance' is known for its disease resistance, which is crucial for maintaining plant health in the challenging conditions of winter.

Data from the U.S. National Arboretum indicates that 'Jasminum nudiflorum 'Sundance' is well-suited to USDA hardiness zones 5 through 9, making it a versatile choice for gardeners across the United States. The plant's ability to withstand cold temperatures and its relatively low maintenance requirements further solidify its status as the best winter jasmine variety for American gardens.