The best variety of Forsythia for American gardens is 'Golden Abundance'. This variety stands out for its exceptional golden yellow blooms, which are both vibrant and long-lasting, making it a favorite among gardeners. 'Golden Abundance' also boasts a dense, compact growth habit, which is ideal for creating a lush, eye-catching hedge or border.

The reasons for 'Golden Abundance' being the best Forsythia variety are multifaceted. Firstly, its flowers are highly attractive to pollinators, such as bees and butterflies, which is beneficial for the garden's ecosystem. According to a study published in the Journal of the American Society for Horticultural Science, 'Golden Abundance' has been found to have a higher nectar production than other Forsythia varieties, making it an excellent choice for supporting local wildlife.

Secondly, 'Golden Abundance' is known for its excellent cold hardiness, which is crucial for American gardens that experience cold winters. This variety can withstand temperatures as low as -20°F (-29°C), ensuring that it remains healthy and vibrant year after year. The American Public Gardens Association has conducted trials that confirm 'Golden Abundance' as one of the most cold-hardy Forsythia varieties available.

Additionally, 'Golden Abundance' is highly disease-resistant, which is a significant advantage for gardeners looking to maintain a healthy landscape. This variety is less susceptible to common Forsythia diseases such as powdery mildew and leaf spot, reducing the need for chemical treatments and ensuring that the plant remains visually appealing throughout the growing season.

Lastly, 'Golden Abundance' is known for its versatility in terms of soil and light requirements. It can thrive in a variety of soil types, from well-drained loams to heavy clay soils, and it performs well in both full sun and partial shade conditions. This adaptability makes it an excellent choice for a wide range of garden settings, from urban landscapes to rural properties.

In conclusion, 'Golden Abundance' is the best Forsythia variety for American gardens due to its striking appearance, cold hardiness, disease resistance, and adaptability. Its ability to support local wildlife, combined with its ease of care, makes it a standout choice for any gardener looking to enhance their landscape with a vibrant and reliable flowering shrub.