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perennials

A massive perennial garden in Colts Neck, NJ laid out, installed and maintained by the author. The key to a perennial garden like this one that will last for years is choosing plants that are acclimated to the area and maintaining them correctly. (Photo provided by author)

 

By Trisha DeStefano

Whether in a commercial installation or residential garden, perennials can offer more landscaping choices (particularly if you’re limited by growing conditions or wildlife), distinguish your firm from the competition and create a niche for your landscape business. The perennial plant trade offers thousands of species and varieties, and that list is constantly evolving. But with such an extensive palette, how do you choose the right plant? Here are three simple rules:

  1. Choose species known to do well in your area.
  2. Read the label. Match the optimum growing requirements; plant the right plant in the right place!
  3. Spend the extra time maintaining each species for its peak performance. Mid-summer trimming and regular deadheading can keep landscapes looking fresh throughout the dog days of summer and keep your maintenance crews busy (making money)!

Basically perennials are plants with a root system that lives through the winter from which fresh growth emerges in spring and dies back to the ground in fall. Most have low to moderate maintenance requirements and no matter how tough the conditions, there is a perennial right for the job: wet or dry, full sun or shade, fertile or poor soil. Many can even grow on steep embankments, hillsides and rocky sites.

It’s not necessary to plant 50 species in one landscape, or always use the trendiest cultivars. A stunning display can be achieved with just five species or varieties that have been in the trade for decades! Familiarize yourself with new hybrids that require less water and pruning, and have fewer pest problems, and an extended flowering time.

The following list includes my go-to perennials with tips on how to keep them going strong throughout the growing season. (See the USDA Plant Hardiness Zone Map at the end of this article for information on Zones described in the content below; zones are shown in color bar at right side of map.)

10 Easy To Maintain Perennials

Agastache (hyssop) ‘Mango Tango’, ‘Peachie Keen’, ‘Rosie Posie’ and ‘Blue Fortune’ etc.

Zones: 5-10, though other species can be grown in colder climates
Size: 18”-30” (some species grow 4’-6’ tall!), 2’ width
Exposure: full sun-light partial shade
Flowers: July-October
Maintenance: Sure to be a favorite, as these perennials are deer resistant, can tolerate moderate to dry soils (must be well drained), and with so many varieties, they’re incredibly versatile! They look great even when finished blooming, but to promote new blooms, deadhead by shearing below the flower spikes. Cut to the ground in late fall.

perennials

Agastache ‘Kudos’ (Kudos Hyssop)

Ajania pacifica (silver and gold pacific chrysanthemum)

Zones: 5-9
Size: 12-20” ht., 12-24” spread
Exposure: full sun to part shade
Flowers: September-December
Maintenance: This great plant has attractive foliage all season long, blooming in fall. Very tolerant of summer heat and humidity as well as poor soils, from normal to sandy or clay with acidic or alkaline pH. Cut back in early spring.

perennials

Ajania pacifica (Silver and Gold Pacific Chrysanthemum)

Allium ‘Millenium’ (Millenium ornamental onion)

Zones: 5-9
Size: 15” ht., 18-22” spread
Exposure: full sun
Flowers: July-August
Maintenance: Millenium’ is one of the very best Alliums! Before the profuse bloom, the shiny, grassy foliage adds texture to the garden. ‘Millennium’ is not bulbous so it grows over the spring and summer. It can tolerate most soil types including clay, and prefers dry to moderate conditions once established. When finished flowering, dead blooms can be cut off. Cut to the ground in fall.

perennials

Allium ‘Millenium’ (Millenium Ornamental Onion)

Amsonia hubrichtii, A. tabernaemontana (bluestar)

Zones: 3-9
Size: 18-36” ht. 20-36” spread (size depends on variety)
Exposure: full sun to part shade
Flowers: May-June
Maintenance: Easy to grow, best in a moist, fertile soil. Can tolerate wet soils for short periods. Not a long bloom time, but the texture, shape, and fall color make Amsonia showy all season. Shear back by one third after flowering to maintain a more compact plant in shadier or overly fertile conditions. Division not needed for 6-10 years.

perennials

Amsonia hubrichtii (Threadleaf Bluestar)

Aruncus dioicus (goat’s beard)

Zones: 3-7
Size: 4-6’ ht., 6’ wide
Exposure: part shade to full shade
Flowers: June-July
Maintenance: Although tall, staking is not necessary. Grow in moist, fertile soil, though Aruncus can tolerate drier conditions in full sun. Deadhead to control unwanted seedlings and prevent flopping. Great for slope stabilization. Division rarely required.

perennials

Aruncus dioicus (Goat’s Beard)

Astilbe chinensis (false goat’s beard) ‘Visions’, ‘Pumila’, etc.

Zones: 4-8
Size: 8”-3’ ht; 1’-2’ spread (size depends on variety)
Exposure: part to full shade
Flowers: July-August
Maintenance: There are other gorgeous Astilbe species, but A. chinensi is most forgiving, able to tolerate drier, less fertile conditions, though in general, Astilbe prefers moist soil in spring and summer, fertilized in spring. If plants dry up, cut back to encourage regrowth when cooler weather and moisture return. If plant crowns lift over the winter, topdress with organic matter. Flower bracts are showy even into winter, so cut back in early spring.

perennials

Astilbe chinensis ‘Visions in Pink’ (Visions in Pink False Goat’s Beard)

Coreopsis verticillata (threadleaf coreopsis) ‘Moonbeam’, ‘Berry Chiffon’, ‘Enchanted Eve’, ‘Starlight’ etc.

Zones: 3-9
Size: 2-3’ ht., 2’ spread
Exposure: full sun
Flowers: June-October
Maintenance: Drought tolerant; requires well drained soil. Vigorous spreader, can divide every 2-3 years in spring or autumn. New plants may bloom all summer without deadheading. Older plants flower in early and mid summer, rest in August then reblooms in fall. For best rebloom, shear plants in August with headge shears or string trimmer to remove dead flower heads. Leave flower heads in fall for winter interest and cut back in early spring. Mulch in zones 3-5 for winter protection.

perennials

Coreopsis verticillata ‘Starlight’ (Starlight Threadleaf Coreopsis)

Geranium sanguineum (blood red geranium) ‘Elsbeth’, ‘NH Purple’, ‘Max Frei’, and ‘Rozanne’, etc.

Zones: 3-8
Size: 6-15” ht., 2’ width (depends on variety)
Exposure: full sun to part shade
Flowers: May-September
Maintenance: Super tough and easy: drought tolerant, can survive in many soils, though do require good drainage. No need to divide, cut back, or deadhead these plants; their initial bloom is heavy and they will sporadically bloom the rest of the season. In late summer when the plants start to look ratty, shear to newly emerging basal foliage, which will turn deep crimson in fall.

perennials

Geranium sanguineum ‘New Hampshire Purple’ (NH Purple Bloody Cranesbill)

Helleborus orientalis (lenton rose)

Zones: 4-9
Size: 15-18” ht., 15” spread
Exposure: part to full shade
Flowers: March-April
Maintenance: The species prefers moist, well draining, alkaline soil with high organic matter content for optimum performance. Lenton roses provide some of the first flowers of the season, and the sepals are attractive for a long time after blooms fade and the deeply lobed, glossy foliage is evergreen. By winter’s end, the foliage is battered. Dead leaves can be pruned off for new growth and flowers. Warm, wet, humid conditions in summer can promote disease; remove and destroy affected parts/plants.

Helleborus orientalis (Lenton Rose)

Hibiscus moscheutos (rose mallow)

Zones: 4-9
Size: 3-8’ ht., 5’ wide
Exposure: full sun to part shade
Flowers: July-frost
Maintenance: Prefers rich, moist soil, good for wet sites. Stems are strong; no staking required. Does not need dividing for 10 or more years and they’re late to emerge in spring. Each flower lasts one day. Deadheading keeps plants tidy and encourages new blooms. Cut stems down after first frost or in early spring. Japanese beetles are crazy for Hibiscus, so be sure to take precautions. It’s worth the trouble; with so many varieties, their enormous colorful flowers, and giant glossy green to deep purple leaves, it’s a showstopper in the landscape!

Hibiscus moscheutos (Rose Mallow)

 

The 2012 USDA Plant Hardiness Zone Map is the standard by which gardeners and growers can determine which plants are most likely to thrive at a location. The map is based on the average annual minimum winter temperature, divided into 10-degree F zones. (Source: USDA.gov)

 

DeStefano is a garden designer and outdoor display horticulturist. She and her husband Rob own GreenCraft Associates, a comprehensive landscape architectural firm based in Hunterdon County, NJ that specializes in high-end residential, commercial, and municipal landscape site planning and design. GreenCraft incorporates sustainable design practices into all of their projects. Providing specialty horticultural services for over 20 years, DeStefano’s field expertise includes the design, installation, and maintenance of perennial, annual, container, and kitchen gardens.

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