Mt. Cuba Center is located near Wilmington, DE, (USDA Hardiness Zone7A/6B). Five plants of each taxon are grown in full sun in a 15,000 sq. ft. trial garden protected from rodents by a 4’ tall wire fence within a 100-acre garden protected by a 10’ tall deer exclusion fence. The clay-loam soil in the trial garden has an average pH of 6.5.

The Trial Garden is maintained with the home gardener in mind. Plants are watered as needed during the first year in order to get them established.  After that, they are left on their own.  Pesticides are not used unless there is a serious threat to the trial’s survivability.

The perennial coreopsis trial ran for three years (2012-2014). Each taxa was evaluated weekly and assigned two scores based on a scale of 1-5 (see below). The first rating was for floral display and was predominantly based on flower quantity relative to plant size and overall appeal. The second rating was for plant/foliage quality and included attributes such as habit, vigor, and disease and pest resistance. These two ratings were then averaged, after which points were deducted for lack of hardiness. A loss of two plants resulted in a 0.1 point reduction of the final rating, escalating up to a 0.3 point reduction for the loss of four plants. A cultivar was not given a final rating if all five plants failed to complete the trial. It was our policy to replace dead plants after the first winter in order to compensate for poor establishment or initial plant quality. However, no replacements were made after the spring of 2013. Hardiness deductions were only calculated based on plant losses after the replacements were made.

Our numerical rating system ranges from one to five and can be interpreted as follows:

  1. Poor
  2. Below Average
  3. Average
  4. Good
  5. Excellent