Perennials
Growing Conditions
Selecting the Plant
Planting and General Care
Seasonal Maintenance
Perennials are any plant that lives more than one season. Herbaceous perennials are admired for their ornamental features as well as their ease of culture. However, that ‘ease of culture’ does not mean that they require NO maintenance. Attention to a schedule of seasonal watering, dead-heading and cutting back will allow your perennials to flourish at optimal appearance and bring texture and colorful foliage and/or blooms to your gardens and containers. There is no specific lifespan for these plants. Some are biennials: plants that grow only foliage the first year from seed, die down over winter and grow again in the spring to bloom, set seed and die. The seeds will germinate and begin the cycle again. Examples would be some varieties of Hollyhocks, Dianthus or Foxglove. Some perennials such as peonies and daylilies can be long-lived perennials that come back year after year. Other perennials such as Polemonium or Chrysanthemums may be considered short–lived perennials, depending on site location, due to our hot, dry summers and lack of snow cover in winter. A particular plant that may be vigorous in your friend’s garden and becomes a nuisance, may behave quite differently in your garden’s different microclimate, different care, even different soil. If you like a plant and it fits in your color or planting theme, give it a chance; in your location you may be pleasantly surprised.
Perennials are a very versatile group of plants with foliage of fine texture (Dianthus Arctic Fire, Astilbe Sprite, Fern Banford Beauty, Iberis Alexanders White, Lavender Munstead, Polemonium Heavenly Habit, Yarrow Credo or Sedum kamtschaticum) or coarse texture (Belamcanda Hello Yellow, Bergenia Winterglut, Coreopsis Sunray, Echinacea Ruby Star, Eupatorium Gateway, Hosta Elegans or Great Expectations, Ligularia Desdemona, Persicaria Red Dragon or Sedum Matrona)
Foliage colors can vary from many shades of green (Yarrow Terra Cotta, Aconitum napellus, Coreopsis Moonbeam or Hosta Guacamole) to golden yellows (Carex Bowles Golden, Heuchera Amber Waves, Heucherella Stoplight, Tradescantia Sweet Kate, Hosta August Moon or Lysmachia Golden Alexander) red/purple (Astilbe August Light, Gaura Crimson Butterflies, Eupatorium Chocolate or Geranium Hocus-Pocus) blue or blue-green (Festuca Elijiah Blue, Dicentra Zestful, Grass Blue Oat Sapphire, Dianthus Frosty Fire, Hosta Elegans or Hosta Blue Cadet) and even variegated or shimmering silver hairs on the leaves creating a silver look in the soft light Alchemilla mollis, Aubretia Whitewell Gem, Arabis Snow Cap, Cerastium Yo-Yo, Fern Japanese Painted, Euphorbia Blushing Bride, Carex Ice Dance, Grass Silver Feather, Hosta Diamond Tiara, Hosta Fire & Ice, Liriope Silvery Sunproof, Polemonium Snow & Sapphires or Yarrow Moonshine).
Plants range in size from mere inches for varieties of ground cover (Thymus coccineum, Ajuga, Cerastium, Dianthus Frosty Fire, Astilbe pumila or Sedum Red Carpet) to over 4-5’ tall for some ornamental grasses, Tree Peony, Eupatorium ‘Gateway’ (Joe-Pye-Weed) and Lily Casa Blanca or Black Magic.
Plants all have their own optimal growing conditions-light, drainage, moisture and exposure. These requirements are generally listed on the label or information sheet next to the plants. Plants will generally grow vigorously and thrive under these ‘ideal’ conditions. Many plants will grow under less than optimal conditions, but will sometimes struggle or be more prone to problems.
Shopping for plants for a particular area around your home, will need a some amount of investigation with regards to the amount of actual sunlight available (Full Sun is 6-8 hours direct sun/Part Sun is 4-6 hours of sunlight/Part Shade is 2-3 hours of sunlight/Shade is less than 2 hours of sunlight/Deep shade is total lack of sunlight). However, a location with full sun from 10am-2pm could be considered Full Sun, as this is the strongest sunlight of the day. Small leaved or thinly branched trees that allow sunlight to ‘dapple’ thru create only part shade. Bright ‘indirect light’ can be found in ‘Open shade’ along a north side of fence or building that has no other obstruction and is suitable for many varieties of Part Shade-Part Sun plants. Also, an understanding of the area’s drainage conditions, whether it dries quickly (hillsides, berms or areas under overhangs), stays constantly moist (swales and bottom of slopes) or is average soil that drains well. The final aspect to check is exposure, whether the plants will be along the East side of a structure or planting windbreak (protection from the Northwest winter winds or along a West property line, fully exposed.
Planting & General Care of Perennials
Bed Preparation: ADD 2 cubic feet of Sphagnum Peat Moss and 5 pounds of Sustane fertilizer per 100 square feet of garden space. TILL in to a depth of 12-18” for average soil conditions. DO NOT TILL IN weeds or live sod as the roots will often re-grow and infest your new garden. Use more peat and Sustane for extra sandy or heavy clay soils.
Container Plants: REMOVE plastic pot completely. Slit sides of root ball vertically ½” in 3 places and 2 times across the bottom. Dead-heading blooms will promote vigorous new root growth. DIG planting hole twice the width of the root ball. PLANT at the same depth as plant was growing in the container. Backfill hole halfway, water in, and finish backfilling completely. Water in thoroughly.
Mulch:Mulch all perennial plantings 2-3” deep with shredded wood mulch.
Watering: Water new perennial plantings every 10-14 days. AVOID OVERWATERING! DEEP watering is important. If you water lightly and often, you will create a shallow root system that will not support a plant during hot dry or windy periods. Established beds (at least 3 seasons) need a deep soaking every 10-14 days, 1 inch minimum each time. (These instructions are for average soil and weather conditions). If your soil conditions tend to be very sandy, watering may need to be every 10 days, if your soil is heavy clay, watering will be more to the 14 day frequency. If plants seem to wilt in mid-summer during the heat of the day, check soil first…if soil feels moist, mist the foliage to help the plant, but do not water unless necessary.
Dead-Heading: Remove spent blooms as they begin fade to encourage longer bloom time and more vigorous roots. Do regularly for the entire season. For fresh cut flowers, cut when blooms are ½ to 2/3 open, in early morning and place in water immediately.
Division: After plants are 3-5 years old, most varieties will benefitfrom dividing.
AS A GENERAL RULE, divide spring and early summer bloomers in Fall (September) and divide late summer and fall bloomers in Spring as soon as plants are up at least 6 inches. The smaller the divisions you make, the longer it will take the plants to recover and grow back to full size.
Early Thaw: Check your plantings in warm spells of winter (such as January thaw) as your plants may ‘heave up’ out of the soil due to freezing and thawing conditions. Gently push soil mound down and re-mulch.
Seasonal Maintenance of Perennials:
Late Winter to Early Spring(Late February-Late March):Remove any remaining foliage, stems and seed heads from beds by cutting back to 2”.Cut-back Grasses to 6” and sub-shrubs to 6-8”.
Early Spring: As new growth appears in beds, spread Sustane fertilizer at 5 pounds per 100 square feet. Also spread pre-emergent herbicide such as Preen at this time. Fluff mulch layer still in bed and topdress as needed to no more than 3” deep after pre-emergent application.
Spring/Summer: Vigorous growing, fall-blooming plants, such as chrysanthemums and some asters need to have growing tips pinched after reaching 6” in the spring and repeat every 2 weeks until July 4th, to delay blooming to late summer and fall. Dead-head spent blooms regularly all season. Remove yellowing or diseased foliage, if it appears, and dispose of in the trash. Water plantings as needed.
Summer: Often after first heavy flush of bloom, many varieties of perennials will elongate and will need to be cut back to control and freshen look of planting. DO NOT cut back plants by more than ½ of foliage growth to avoid excessive stress. Plants will recover more quickly if left with sufficient foliage. In late July to first of August, do a second fertilization with Sustane at 5 pounds per 100 square feet and a second application of ‘Preen’ to help control weeds into fall.
Late Summer to Fall: Many late season blooms (Shrub Roses, Coreopsis, Echinacea, Asters, Sedums, Grasses) can be allowed to go to seed to feed the birds in the winter as well as add interest to borders in winter. Some plants such as hardy Geraniums, Heucheras, Tiarellas and Vinca minor will add to winter with evergreen or colorful foliage. As foliage begins to yellow, remove from beds. As late fall frosts set in, remove any ‘water-soaked’ foliage to prevent smothering crowns of plants. Leave sturdy plants stand till early spring and topdress mulch as needed.
