Selecting and Planting Perennials
Discover how perennials can brighten your garden with this guide on how to choose the best ones for your outdoor space.
Perennials provide spectacular flowering displays for many months of the year. Although some tall types require staking, most will look after themselves, reappearing year after year following their winter rest. Here's how to make perennials work in your garden.
From the towering Eupatorium purpureum to the low, sprawling Campanula poscharskyana, there is a perennial for any area or planting design. They are available in a huge range of colors and shades, making it difficult to decide which to plant. Begin by assessing your site and soil and selecting those that do best in these conditions. Next, map out your border or planting area, and assign plants according to their size and stature. Generally, lofty plants provide a backdrop to medium-sized and ground-hugging perennials, but remember that a few, such as the ever-popular Verbena bonariensis and elegant Dierama pulcherrimum, can be planted toward the front of a design because they have slender stems and an airy, see-through structure. Finally, take your pick from the wide range of flower colors and foliage varieties to complete your design.
For borders bursting with color, include a few flamboyant blooms. Try peonies, which boast large flowers prized for their ruffles of delicate petals in pink, red or white. Lupines join the peonies in early summer and produce eye-catching cones of small flowers in many hues, while in midsummer, the towering spires of delphiniums are hard to beat with their spikes of open flowers in shades of blue, purple, pink and white. Also add a selection of oriental poppies. Although their sumptuous blooms are relatively short-lived, the decorative seedheads that follow extend their interest.
Planning a Long Season of Interest
There are perennials for all seasons, starting with hellebores, which flower between late winter and mid-spring. Next are the dainty forget-me-not-like blooms of brunnera, and dancing flowers of epimedium and Dicentra spectabilis, all of which prefer some shade, followed later in spring by columbine in a variety of shapes and colors. A host of geraniums and vibrant avens then appear in the early summer. For dramatic color from late summer to fall, opt for blue or red asters and golden black-eyed Susans, toned down with the white daisies of Leucanthemum. In the fall, try the knee-high, sun-loving Ajania pacifica, which bears yellow button-like flowers surrounded by beautiful silver-edged lobed foliage. The evergreens then come into their own in the winter, with round-leaf bergenias and colorful heucheras leading the show.
Planting Depths Explained
Most perennials should be planted at the same depth as they were when in their original pots, but exceptions include those that dislike damp soil around their stems, such as Verbascum, Sisyrinchium and sedum. Plant these 1 to 1-1/2 inches above the surface, and pull up the soil around the root ball to encourage water to drain off. Moisture-loving plants, including hostas, prefer to be planted more deeply so that their roots are never exposed to the dry conditions nearer the surface.
Perennials for Difficult Sites
Versatile and beautiful, perennials can be relied upon to fill even the most challenging sites. Plan carefully, and you will be able to create year-round interest in any garden.
Alpines are perfect for squeezing between paving or the gaps in a dry stone wall. Aubrieta, Alyssum and Arabis will fill these areas with exhilarating spring color, while Frankenia and Cerastium offer later seasonal interest.
The grayish blue-leaf evergreen Euphorbia rigida is ideal for sunny slopes and produces frothy yellow flowers in spring, or choose the fernlike, silver-leaf Artemisia ‘Powis Castle’ for sun-baked gravel gardens.
In dry shade, use the pretty Vinca minor, with its waxy stems of evergreen foliage and beautiful blue spring flowers, or Lamium, with variegated foliage.
Most ferns are at home in deep shade, while other good choices for shady borders include low-growing Pachysandra, Alchemilla mollis, and brunnera, or Bergenia and Lysimachia where taller plants are required. For damp shade, try hostas, which produce attractive foliage (but most need protection against slug and snail attacks).
If you plant perennials in their optimal conditions, they should only need watering for one season after planting. Some may require extra irrigation during extended periods of drought, but don’t be tempted to water plants whose leaves droop at midday, because this is simply their mechanism for conserving moisture — they should bounce back again in the evening.
Once they are established, hungry perennials, such as Aster novae-angliae, will need an application of all-purpose granular fertilizer once a year in spring. Also mulch around perennials with organic matter, such as well-rotted manure, compost or bark chips, at the same time.
Tall plants, such as delphiniums and some asters, will need staking, especially in exposed sites. Insert stakes in spring when new growth appears, and tie in the stems as they grow. Stake single stems with bamboo canes; insert hazel twigs or pea sticks, or use link or ring support frames around clump-forming plants. These may not look very attractive at first, but the plants will soon grow large enough to disguise them.
Cutting Back Perennials
Perennials require very little other maintenance, and most will be happy doing their own thing for the rest of the growing season. Some plants, such as hardy geraniums, will form fresh foliage if you cut them back after they have bloomed. Others, including dianthus, will produce a fresh flush of blooms if deadheaded. In the late fall, cut old plant stems down to ground level unless their foliage or seedheads are attractive over the winter, in which case wait until spring. Remove the old foliage of evergreens, including bergenias, in the spring to allow space for new leaves to form.
The Chelsea Chop
In late spring, you may want to try what is known as “The Chelsea Chop.” Simply cut or pinch back plants by half. This technique makes them bushier, and plants will also produce more flowering stems, so although they will bloom a little later than usual, the display will be more spectacular. Plants that respond to this include sedum, black-eyed Susans, Echinacea and sneezeweed.