When gardeners converse, the words border and perennial are frequently uttered together. They may be talking about gardens known as perennial borders, or border perennials, as the herbaceous perennial plants traditionally grown in those beds came to be called.
Herbaceous perennials – generally, plants that die back to the ground in cold winter weather but resume growing in spring – offer gardeners a mind-boggling selection of plant size, flower color and form, and season of bloom.
This smorgasbord of choices means that a well-designed border of herbaceous perennials can be a spectacular feature in a garden. But for most gardeners, border perennials are probably at their most useful in a mixed border, in which perennials are inter-planted with woody plants – plants that have woody stems, though they may or may not lose their foliage in winter.
In recent decades, as ideas about gardening have changed, many gardeners have opted to take their cue from nature, interpreting in the garden the layering tendencies of plants in the wild. (If you’ve ever looked at the area where woods border a field, you’ve seen these layers – tree canopy, understory trees, shrubs, herbaceous plants, and groundcovers.)
Mixed borders give a nod to this concept, allowing woody plants to add structure, height, texture and year-long interest to the garden.
“I feel it important that a border have a backbone, so that in the bleak of winter and also through the seasons, the garden looks interesting, alive and pulled together,” says Grace Romero, chief horticulturist for W. Atlee Burpee & Co. “Since most perennials come into and out of their peak seasons, small conifers, trees, and shrubs such as hydrangeas, physocarpus, caryopteris, roses, spiraea, weigela, cornus and viburnums tend to fulfill this function and provide structure.”
Of course, the overall size of your property, the amount of sun it gets, and its climate zone will dictate which woody plants you can grow, and which perennials, too. It’s easier to be successful as a gardener if you grow plants suited to the conditions in your garden, rather than trying to force plants to adapt to inhospitable sites. However, to accommodate the needs of urban or suburban gardeners with smaller plots, plant breeders in recent years have introduced downsized versions of a wide variety of conifers and shrubs, so there’s no shortage of options.
Once you have established your garden’s bones, “the ‘second skin’ for a border could include textural, mid-sized specimens such as amsonias, asters, shastas, monarda, grasses, daylilies, or hibiscus,” Romero adds, and you can flesh out the border with “anchors and filler plants such as gaillardia, coreopsis, salvia, sedum, veronica, heuchera, geranium, iris, dianthus and achillea.”
Borders don’t have to actually border a yard or lawn, or a path. They can be any shape you want, with well-defined edges and geometric design or with curving lines and effusive perennials that spill onto a path. For flowering continuity, choose perennials that will bloom at different times throughout the season – and keep what-blooms-when in mind as you design your border.
In general, the tallest plants should be towards the back (or the center, if it’s an island bed), mid-size plants in the middle and the lowest perennials in front – but don’t be too rigid about this, or your border may look like stadium seating.
You can design a perennial or mixed border to highlight color, or fragrance, or texture. You may want a border filled with shade-lovers or plants that have low water requirements. Or maybe you crave a border that will attract hummingbirds and butterflies.
Drought-tolerant plants include lots of sun-lovers that work well in many borders, such as artemisia, aster, baptisia, campanula, chrysanthemum, coreopsis, echinacea, gaillardia, gaura, hemerocallis, kniphofia, lavender, liatris, rudbeckia, sedum, and solidago.
Some of those perennials also work well to attract butterflies and hummingbirds. Monarda and cardinal flower are two favorite nectar sources for hummingbirds, which tend to like long, tubular flowers in bright colors such as red, orange and yellow. But to keep the birds coming all season, you need to plant perennials with overlapping bloom times.
Remember that if you want butterflies to grace your garden, you should also have host plants for the caterpillars that are part of their life cycle. Coneflowers, phlox, asters, daisies, salvias, sedum, zinnias, and eupatorium all attract butterflies, plus both common and swamp milkweed and butterfly weed, and just about any plant in the carrot family.
Plant tags, garden catalogs and web sites should provide you with all the information you need to choose perennials that fit your requirements, but you can also check out some excellent books on perennials, such as Allan Armitage’s color encyclopedia of garden perennials, or The Perennial Gardener’s Design Primer by Stephanie Cohen and Nancy J. Ondra.
And as Cohen and Ondra advise, don’t worry too much about the “rules” of perennial borders. The idea, after all, is to have fun and to create a border that pleases you.