Starting in 1977, each year Michigan State University Department of Horticulture’s Annual Trial Gardens has evaluated hundreds of new annuals grown from seed or cuttings. In 2015, trial selections were supplied by 36 private breeding companies and the plants were grown in MSU greenhouses and transplanted into either ground beds or containers after the last frost passed, which in 2015 was May 25 to June 9.

The performance of each plant in the trials is evaluated bi-weekly by MSU Horticutlure Gardens staff on vigor, uniformity, ornamental value-flowers and foliage. In addition, disease and insect susceptibility is noted as well as effects of the climate that season. Plants are rated on a 1.0 (poor) to 5.0 scale with 5.0 being exceptional performers. The purpose of the trial is to grow and evaluate new and old species and cultivars under mid-Michigan growing conditions that include, in most years, cool springs, hot-humid summers and a frost-free period from mid-May to early October.

All transplants are greenhouse-grown and no plant growth regulators are used. After transplanting to beds or containers, they are fertilized every two weeks and hand-watered as needed. No treatments were given in 2015 for insect or disease control in the annual gardens. Other than spider mites on the dahlias and typical damage from Japanese beetles, relatively few troublesome insects or diseases were noted this year.

Approximately 36 plants had an average rating of 5.0 for the entire 2015 trial season. Plants that were the best included 10 begonias, seven coleus, three petunias and four portulaca. See the full list of the top winners and best in class, download a PDF at: 2015 Top Performers at MSU Horticulture Gardens.