Inside the catmint trial

Under the auspices of the RHS, dedicated plant committees and trials teams grow different varieties of the same plants under controlled conditions, providing gardeners with unrivalled information. Judge Val Bourne reports from the Nepeta Trial

- Val Bourne

ONE of the most useful—and least trumpeted—services provided by the RHS is its Plant Trials. Many varieties of the same plants are grown side-by-side in controlled conditions at RHS sites around the country and observed by expert members of the relevant Plant Committees, sometimes over several years, to see how they perform. Varieties are judged on a wide range of criteria and the best will be given the RHS Award of Garden Merit (AGM). Plants range from favourites such as catmint, the subject of the trial we report on today, to the new and less well known and the results are published, free, online, so all gardeners can look up to see which plants will work best for them.

The current Nepeta Trial, being held at RHS Wisley, showcases more than 120 varieties of catmint from a total of 250 species found in Europe, Africa and parts of Asia. It includes established stalwarts, such as ‘Six Hills Giant’, alongside brilliant new introductions, including ‘Summer Magic’ and ‘Hill Grounds’. Some varieties definitely fall into the catmint category, with clouds of tiny soft-blue flowers rising above aromatic grey-green foliage. Others have showy, darker blue tubular flowers and green leaves, which indicate a need for better soil and a tolerance of partial shade. A third variation on the theme, Nepeta nuda, offers branching heads of pale flowers on tall, very upright sultry stems. These are suited to prairie planting, offering structure and winter silhouette, although they’re not very widely grown—yet.