May is a good month for planting perennials. In milder, drier springs, April is even better, but I suspect a lot of gardens were unfit this year for April planting. Plants are abundant at nurseries and garden centers and should still be in good shape, bursting with growth potential. Some perennials are available in both 4-inch pots and gallons. Four-inch plants are cheaper and they tend to take off fast, sometimes making up the size difference in a matter of weeks.
Perennials provide some of gardening’s greatest opportunities for artistry. There is almost no end to the amount of ambition, skill and creativity you can put into it if you choose. Perennials vary radically in size, growth rate, longevity and character. Most bloom for a relatively short time — a week, two weeks, maybe a month. So a satisfying border of perennials must take time into account as well as shape, height, texture and flower color.
The pay-off is a border that changes constantly but always puts on a good show. The smaller the area, the harder this is to achieve. On the other hand, big perennial gardens can be a lot of work. What’s more, they don’t offer a great deal to look at in the winter, even in our benign climate. Luckily, there are a few considerations that help make smaller borders satisfying. Small-garden perennials don’t have to be small, but it helps a lot if they share certain characteristics.
Any perennial you put in a small space should have at least two of the following qualities, and preferably more: 1) You love it, 2) It blooms for a long time, or reliably re-blooms, 3) It does not need frequent division to perform well or to remain in scale, 4) It has attractive leaves or is otherwise nice to look at even when it isn’t blooming. New shoots, buds, dead flower stems and even dry leaves can all be interesting features.
Leaves often don’t seem that important to beginning gardeners, but their significance becomes apparent over time. There is a story told about a famous British gardener and consultant, when he was asked to comment on a border that the owner was unhappy with. After walking up and down a bit, GST pronounced, “Your leaves are all the same size.” It’s true that many classic border plants have rather boring, medium-sized, medium-green leaves. It makes a huge difference to mix it up: Look for large leaves, colorful leaves, dissected or “ferny” leaves, teeny leaves, long and narrow leaves.
Lastly, life will be simpler if your plants are well adapted to the conditions in your garden and have no very special needs. I consider a need for staking a special need. I don’t do it. Some plants look quite nice when they flop, sprawl and clamber, but generally I expect plants to stand up by themselves and stay more or less in the spot assigned to them. For a bit of drama, I like to include a tall grass or a canna lily. Or both. Even in a small bed.
My A team includes, for their long bloom period, Geranium “Rozanne” (blue flowers, and I do mean blue) or “Anne Folkard” (magenta). They sprawl and climb, but in a delightful way, and the roots stay in a clump. Aster x frikartii is almost as long-blooming, and does not “run” the way so many fall asters do. And the lavender blue flowers go with just about everything. Phlomis russelliana spreads a little faster than you’d like, but the leaves are cool and the flowering stems look great before, during and long after.
Taller plants that stand up straight and don’t run include Achillea “Coronation Gold” and Culver’s root (veronicastrum). Whether echinacea will stay put depends a lot on your soil, but I love the variety with ivory flowers, and they seem pretty static. Peonies and lupine-like baptisia bloom early in summer and are soon over, but they have handsome leaves and rarely need dividing.
Narrow leafed classics are crocosmia and daylily (both expand rapidly), kniphofia (torch lily, poker plant: expands more slowly) and iris, especially Siberian and Japanese (Iris ensata). Although I prefer the graceful Siberians, I plant Japanese more often. The clumps expand at about the same rate and share an all-too-brief flowering season. But I. ensata stays roughly vertical, while Siberians soon make enormous, arching leaf clumps — a good feature where there’s room for it, but sometimes a nuisance in tight quarters.
If you are afraid of grasses, I recommend trying variegated purple moorgrass (Molinia caerulea ‘Variegata’), a demure, stripy, trouble-free, front-of-the-border plant. It loses its leaves in winter, so you don’t need to remember to cut it back in January. And you won’t ever need a backhoe to get it out.