In this case the use of Nepeta has many uses...its amazingly colourful, flowers nearly all summer and early autumn, is scented, and its amazign at attracting beneficial insects to a garden, hense its close proximity to the greenhouse.
The nepeta today was alive with bees....by there thousands along it, and these bees (and other bugs) will help to polinate the peaches and other tender greenhouse fruits which live in the greenhouse.
You can try thuis yourself by planting some Nepeta Walkers Low beside your greenhouse, or even beside your rose bushes to help reduce greenfly....