Heading into a crowded nursery and being confronted by row upon row of potted perennials can be a daunting experience for even the most seasoned gardener. Buying perennials should always be considered a long-term investment, so it's important to choose judiciously. Fortunately, plant tags usually give general information about mandatory light levels (from deep shade to full sun), moisture requirements (from dry or well-drained to boggy), as well as hardiness zones and plant size at maturity. (If this information is inadequate or missing, be sure to ask the sales staff.)
The problem that remains, though, is how to separate the wheat from the chaff and choose the best plant in the bunch.
1. When surveying a potential purchase, the first thing I look at is the soil: germinating weed seeds, moss or liverwort (Bryophyta spp.) that choke the soil surface are often signs of a neglected or poorly grown plant.
2. Next on the checklist are insects and disease. If lifting up the potted perennial sends an army of sowbugs or earwigs scurrying in every direction, this is an indication of a poorly maintained plant and may point to the presence of other less easily detected pests. Plants with leaf spot, rust or other foliar blotches and blemishes may harbour plant fungi or disease and should be passed over in favour of perennials with turgid, healthy, evenly green foliage.
3. The debate over whether or not to buy perennials when they're in flower is still being waged, but several species (particularly peonies and irises) suffer chronically from inaccurate labelling, so I prefer to buy them when they're in bloom, then remove the flowers before planting. This process, known as disbudding, ensures that your new perennial will focus all of its energy on establishing a healthy root system during its first season, in preparation for a floriferous future.
4. From there, my gaze shifts upward, but only about an inch, as the next area to investigate is the crown, where root, soil and stem meet (see page 2 for a description of what to watch out for).
5. Most perennials will appreciate having their roots gently loosened at planting time. If you do buy a completely pot-bound plant, rather than scoring and slicing its roots, simply divide it into two sections before planting.