Perennials bloom at different times and come in seemingly endless varieties, habits, flowering forms and colors. Annuals certainly have their place, and many are beautiful, but the recurring costs make them more expensive in the long run, and they usually require more watering, fertilizing, deadheading and staking. Perennials generally don't flower as long as annuals, but keep in mind other traits as well, from leaf ornament and plant form to overall texture and even fall color.
Perennials have been central to the shift away from static, formal gardens of foundation shrubs and bedding plants to places of dynamic beauty that evoke nature, even on the city balcony. Where once the nursery's perennial section consisted of hostas wrapped in tarpaper or peonies in pots, whole areas now are devoted to hundreds of perennials in all shapes and sizes.
Divide and Conquer
Most perennials will need dividing, in some cases after just two years (as with certain daisies) but usually in their fourth or fifth season (as with daylilies and coreopsis). Digging up a mature clump of perennials, separating it into segments with new stems and roots and discarding the old core is an effective way to keep plants vigorous, free-flowering and disease-free. Since one old plant can generate four or five new plants, it is also an inexpensive and rewarding method of expanding your plant stock and sharing the surplus with others.
You will know a perennial needs dividing by its crowded look and the diminishing number and size of its flowers. Generally, early fall is the best time to divide, after the season's growth and before the winter halts root development of young divisions. Remember not to try dividing a plant while it is still in the ground.
Different plants have different structures, Some have roots leading to stems, others rhizomes or tubers between the stems and the roots proper. Whichever kind you are working with, look for the little nubs, or "eyes," near the crown that will become the new stems of the following spring, and dissect the plant so that one or more nub is left intact on each division.
Some clumps are best separated gingerly by hand, while others need encouragement with a sharp penknife. Some perennials have thick, fibrous roots and require much effort to split them up. Split them with a hatchet or cleaver, being careful to keep stems (and fingers) intact.
Know where you are going to put your new babies before delivery, and be prepared to plant them and give them a good soaking within a few hours. If you can't plant them for a day, soak them overnight (but no longer) in a bucket of water with a solution of Miracle-Gro or its equivalent diluted to half strength.
Staking If perennials need staking, consider whether they are worth growing. Some are worth the effort, notably peonies, asters, garden phlox and salvia guaranitica. Often, like asters, the plant simply needs twine tied around its outer stems to keep the stalks from slumping to the ground. Tall, skinny plants such as oriental poppies may need tying to a bamboo cane, driven a foot into the ground. Yet others, like peonies, will prefer a cage of wire or twine to grow up into.
If you decide that a plant needs staking, the best time to do it is before the stems are beaten down by wind and rain, or, better yet, just as the plant begins its spring growth. A perennial that is staked after it has grown leggy and become battered never looks as natural or attractive as one staked preventively. Typically, a perennial that grows to three feet or higher may need staking.
To avoid plants becoming leggy, place them in sufficient sunlight and deadhead the first flush of blossoms once they finish flowering.
10 Recommended Perennials
Our 10 recommended perennials were picked for their ease of care, pest resistance, long flowering period and beauty. While space does not permit every worthy perennial to be discussed, the plants included here are proven components of splendid Washington-area gardens.
1) Cranesbill
Cranesbills, or hardy geraniums, form lovely mounds of cutleaf foliage. They grow to a height of 12-24 inches. Most bloom from mid-to-late spring and early summer, though some flower in late summer. Popular varieties include Johnson's Blue (violet blue), Ingwersen's Variety (pale pink), Claridge Druce (rose pink) and Geranium sanguineum striatum (light pink).
Uses:Interesting foliage makes it a welcome addition.
Care:Plant in full sun, 18-24 inches apart.
2) Daylily
Daylilies bear a close resemblance to true lilies, but they are entirely different plants. As their name suggests, daylily flowers last for less than a day. There are tens of thousands of varieties in almost every size, shape, habit and flowering period.
Uses: A garden staple, the daylily grows famously from Louisiana to Maine, shrugs off pests and disease and lends itself to easy hybridizing.
Care: The daylily's biggest need is water, especially during the critical growing period. A good soaking once or twice a week as the buds develop in June will ensure many blooms.
3) Japanese anemone
The Japanese anemone's maple-like leaves grow throughout the season. Beautiful blooms then emerge from late summer to early fall. Popular varieties: Honorine Jobert (white), September Charm (pink) and Alba (white). They grow to a height of two to three feet.
Uses: Its September flowering makes the Japanese anemone indispensable to gardeners.
Care: Space plants two feet apart in partial shade.
4) Purple Coneflower
These are huge (three to four feet tall), daisy-like flowers that bloom in early to mid-summer, with rose-lavender petals radiating from a bronze-orange disc.
Uses: Showy and carefree, purple coneflowers thrive in narrow beds.
Care: Space two feet apart and plant in full sun. Avoid damp soil.
5) Dianthus (Pinks)
There are dozens of ancient (and modern) varieties of garden pinks, with colorful late-spring blooms in white, pink, crimson and magenta. Their foliage grows as evergreen buns or mats of leaves in a range of colors, including blue-green and silver. Pinks grow between 12 and 18 inches tall.
Uses: Easy to place with other perennials, fragrant when in bloom and highly ornamental when out of bloom.
Care: Plant in full sun or partial shade, 12-18 inches apart. Plant in free-draining soil to avoid crown rots.
6) Sage
Sage comes in colors from white to indigo, and can grow as tall as three to five feet. Its attractive foliage makes it a handsome companion to other sun-loving flowering plants. Look for Salvia x superba, mealy cup sage, Salvia argenta, Salvia gaurantica, and, for cooking, Salvia officinalis.
Uses: This diverse group of plants includes sage used in cooking and Victoria sage that brings spring freshness and color all summer and into fall.
Care: Sages generally prefer full sun (a little shade is okay) and well-drained soil that isn't overly rich.
7) Japanese iris
Japanese irises are revered in their native land, and it is easy to see why. The summer flowers are big but delicate, like giant butterflies floating on air. They typically are six inches wide but can be as broad as ten inches. The netting and veining of the petals on certain varieties is unlike anything else in the flower world.
Uses: Easier to grow and to place with other garden plants than bearded irises.
Care: Japanese irises prefer slightly acid, humusy soil and a sunny location. They will flourish in standing water during the growing months. Divide every three to four years.
8) Speedwell
This is a valuable, long-flowering summer perennial. It grows between one to six feet tall, by variety, and comes in blues, pinks, whites, and violets.
Uses: Smaller and dwarf varieties can be used as vertical accents in mixed borders. Larger varieties should be placed in the back of the border.
Care: Speedwell prefers ordinary, well-drained soil that is neither too poor and dry nor too rich and wet. Plant in full sun or partial shade, 12 - 18 inches apart.
9) Coreopsis
Moonbeam (pale yellow) is the best known variety of this early summer-to-fall bloomer. Also look for the lower-growing Zagreb (a stronger yellow), and C. rosea (pink with yellow-green centers).
Uses: Tall, larger-flowered C. grandiflora is useful for perennial beds or wildflower meadows. Low, growing mounding threadleafs (C. verticillata) are great as fill-ins around larger perennials and small shrubs.
Care: Plant in full sun to partial shade, 18 inches apart.
10) Peony
The large silky flowers of the peony come in soft pastel colors,magentas and hot pinks. Most popular garden varieties are doubles–dozens of ruffled petals with no discernible center–that are bred to be eye-catching and long lasting.
Uses: A star of the late spring garden, the peony can be employed as a low hedge or as part of a broader garden composition.
Care: Peonies are best planted in the fall. They will flower longer and retain more of their color if given a little dappled shade in the early afternoon.
Perennials for Dry Areas
Inevitably, there are garden areas that have poor, dry soil, and are in full sun in July and August. Yet these beds need not be eyesores. The perennials below are generally pest-free and disease-free, and when planted with similarly ironclad ground covers and ornamental grasses, produce a beautiful landscape.
Goldenrod (Solidago): Goldenrod grows to one to five feet (depending on variety), producing yellow flowers in later summer. Some consider this a weed, but there are lovely cultivars to chose from. It is often confused, inexplicably, with ragweed.
Sedum: Another late-summer bloomer, the fleshy sedum looks great massed in the company of creeping junipers, St. John's-Wort and dwarf grasses and in front of and between shrubs. Look for Autumn Joy, Ruby Glow and Brilliant.
Yarrow (Achillea): Yarrow is a little like Queen Anne's lace but with tighter, yellow flower heads and ferny foliage. As beautiful as it is tough, yarrow, which flowers for several weeks in early summer, deserves to be planted en masses. Varieties to look for: Coronation Gold, Gold Plate and Hope (Hoffnung).
Rudbeckia: Related to the black-eyed Susan (which is short-lived), rudbeckia's best variety is Goldsturm. Though used a lot, it is a wonderful, tough, long-blooming summer flower.
Purple coneflower (Echinacea purpurea): This falls in the same category as rudbeckia. It may be a little trite, but it is marvelous for those difficult summer beds.
Gaura lindheimeri: This is an underused native plant that is great for hot, dry spots. It sends up weeks of flower spikes with attractive, small white blooms.
False indigo (Baptisia australis): False indigo grows like a shrub, with pretty blue-green leaves and dark, indigo flowers clustered along showy spikes.
Plume poppy (Macleaya cordata): This is an upright, back-of-the-border, summer bloomer.
Penstemon barbatus: A useful if short-lived native plant, this species is noted for attracting hummingbirds. Look for an award-winning variety named Husker's Red.
Rose sundrop (Oenothera): Pink-flowering and low-growing, oenothera can do too well, becoming invasive. It is useful as a fill-in plant in hot corners or on embankments.
Perennials for Damp Areas
Especially damp areas can be problematic for gardeners. Yet there are perennials that welcome and thrive in wet soil. Those listed below are attractive and hardy additions to an area which combines full sun and damp ground.
Rose mallow (Hibiscus moscheutos): A large, showy hibiscus, this variety emerges in mid-to-late summer-with flowers the size of dinner plates.
Gooseneck loosestrife (Lysimachia clethroides): This forms attractive clumps, about three feet high, with long-blooming white inflorescences in mid-summer. It can be invasive.
Mints (Mentha): There are many mints from which to select. Popular varieties include spearmint (mentha spicata), peppermint (M. x piperita) and pineapple mint (M. suaveolens variegata).
Joe-pye weed (Eupatorium purpureum): Fabulous for the naturalistic garden, it is noted for drawing butterflies. It grows tall and flowers in late summer. Look for named cultivars.
Deer grass (Rhexia virginica): A swampland plant, deer grass grows on upright stems to 18 inches and blooms in late summer. The flowers are rose pink.
Turtlehead (Chelone obliqua): The native turtlehead, a late-season, pink-flowering perennial, benefits from some shade in the afternoon.
Cardinal flower (Lobelia cardinalis): Growing four feet high and capped with nodding bell flowers in rich scarlet hues, the cardinal flower is another useful native plant for attracting wildlife, particularly hummingbirds.
New York ironweed (Vernonia noveborancensis): A willing native for low-lying meadows, this plant flowers in late summer on five-foot stems. It makes a good companion to other natives and is not for formal gardens.
Cutleaf coneflower (Rudbeckia laciniata): This is another late-flowering native plant suited to natural plantings. It is tall-growing to six feet or higher. Another species, R. nitida, is a good substitute. Look for Goldquelle.
Knotweed (Polygonum): Two knotweed species are planted by connoiseurs afflicted with damp soil, Firetail (Polygonum amplexicaule) and Superbum (P. bistorta). Both will take partial shade, too. They are distinguished by their showy, bottlebrush flower borne on long stems above leathery foliage. Superbum flowers in early summer, Firetail in late summer.
Perennials for Shade Gardens
Many perennials do well in the shade garden. Large retail nurseries have whole areas reserved for them, growing under shade cloth. Also, visit public gardens to see what is flourishing in the shade. Shade-loving perennials generally are free of pests and diseases, except for slugs that can damage dead nettle and wild ginger.
Virginia bluebell (Mertensia virginica): This is a handsome native plant suited to the damp shade garden, but add lots of leaf mold to the soil. It flowers in April and May.
May apple (Podophyllum peltatum): A showy native ground cover, may apple is one of the delights of the spring woodland garden. It is a deceptively big plant, with leaves a foot across, and a colony needs room to spread. It is great at the feet of woodland shrubs and goatsbeard.
Goatsbeard (Aruncus dioicus): Resembling an oversized astilbe, goatsbeard is an underused perennial that thrives in moist, semi-shaded conditions. It can be used as a specimen in the smaller garden or en masse on larger properties.
Astilbe: With their decorative, lacy foliage and plumes of flowers, astilbes make fine perennials for shade-except that they resent wet soil during their winter dormancy. This can be fixed if you raise up damp spots with plenty of organic matter, Astilbes look best in a group of at least five. The pinks and reds can be dramatic, and you can't go wrong with white varieties.
Dead nettle (Lamium): This member of the mint family comes in many attractive varieties suited to massing in the moist woodland setting. It is mainly a foliage plant, and silver-leafed and variegated varieties are useful for brightening garden dark spots. Look for Beacon Silver.
Corydalius lutea: This is a finely textured plant for shade, with lots of tiny yellow flowers. Amend the soil as with astilbes.
Euphorbia palustris: Difficult to find bit worth seeking out, this perennial has shrub-like qualities, mounding to three feet, and is superb in habit and texture. It is best massed. It also is marginally hardy in our area, so mulch after cutting back the foliage in late fall.
Japanese butterbur (Petasites japonicus): A large, spreading plant with huge, lotus-like leaves, butterbur also is valuable in wet spots where little else grows. It needs lots of room and, once established, is hard to eradicate. The leaves can be three feet across. It is a good background plant for the banks of a large pond.
Wild ginger (Asarum): A terrific, low-growing foliage plant for light to deep shade, wild ginger is well suited to small gardens and shady nooks in larger ones. The most common type is the glossy-leafed European wild ginger, but look for interesting native species, too.
Hostas: Hostas are grown for their foliage ornament, though many varieties have flower spiked with bold decorative effect, especially when planted en masse. Some varieties, such as Gold Standard and Royal Standard, are suited to deep shade, but generally hostas perform best in partial, dappled or high shade.
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