The best plants for zone 6 are those plants which are specifically designed or bred to be grown there. Hardiness zones, which were established by the U.S. Department of Agriculture in the 1990s, establish average annual minimum temperatures for an area, based on averages taken over the twelve-year span from 1974 until 1986. Each zone is divided into two sub-zones for further specificity.
Hardiness zone 6a includes areas where the average annual minimum temperature -- the average coldest temperature the area will experience throughout the year -- is between -10 and -5 degrees Fahrenheit, including cities like St. Louis, Missouri and Lebanon, Pennsylvania. Hardiness zone 6b includes areas where the average annual minimum temperature is between -5 and 0 degrees Fahrenheit; this includes cities like Branson, Missouri and McMinnville, Tennessee.
When you're planning to invest your time and money into a landscape or a garden, you'd do well to verify that the plants that you purchase and plant are specifically designed to grow in your region. Because if you attempt to plant something that's best suited to hardiness zone nine in hardiness zone 6, you'll quickly find it dead.
Most vegetables can be grown in a variety of hardiness zones. What matters, however, is when you plant them in those zones. For example, in zone four, asparagus can be planted anytime between the middle of February and the beginning of April while in zone 6, it should be planted anytime from mid-April and mid-May.
Many garden guides are available to provide you with an accurate planting guide based on your hardiness zone. If you follow the guides, you'll increase your chances for success, especially for tender plants. For example, if you plant collards too late in the year, they could be susceptible to damage from early frosts.
In hardiness zone 6, you can plant any of a number of flowers. As with vegetables, you should ensure that the specific species and cultivar of that species that you've purchased is perfectly suited to your climate.
At least three cultivars of the hybrid tea rose are suitable for hardiness zone 6, including the 'Rosa Tiffany,' 'Rosa Tropicana,' and the 'Rosa Sutter's Gold." Tulipa Schoonoord, a variety of tulip, is also perfect for hardiness zone 6. You could plant pansies, hyacinths, and Shasta daisies. This list is, of course, not exhaustive: hundreds of flowers and cultivars are well-suited to hardiness zone 6.
If you're looking for the best trees to plant in hardiness zone six, check out trees like the Lawson cypress (Chamaecyparis lawsoniana) and the convex-leaf Japanese holly (Ilex crenata 'Convexa'). Look into planting the Yoshino cherry tree (Prunus yedoensis) or the Japanese stewartia (Stewartia pseudocamellia).
The best advice that you can receive when considering the best plants for your hardiness zone is to plant species that are native to the area. Instead of finding species and cultivars that have been bred to withstand Branson, Missouri's climate, look to flowers and trees that are native. These plants are perfectly tailored to grow in your climate and in your specific conditions. Because a hardiness zone accounts only for average annual minimum temperatures and not for other conditions, such as soil content and humidity, it will be more difficult to find plants more perfectly suited to your area than native plants.