20 best perennial plants ❚ All products were chosen independently by our editorial team. This review contains affiliate links and we may receive a commission for purchases made. Please read our affiliates FAQ page to find out more. This competition is now closed 20 best perennial plants Perennials are the largest group of garden plants and offer magnificent diversity for every location from sun to shade. Plants range in size from ground-covering and clump-forming varieties just a few centimetres high, right up to statuesque giants a couple of metres tall. Growth is quick and most plants reach a mature size within one or two growing seasons. Perennials mostly flower in spring, summer, or autumn, with a handful blooming in winter, and many have attractive foliage too.