Designing, installing perennial gardens


For the home gardener, the term Perennial means a plant with stems that usually die back in winter and a root system from which new foliage and flowers grow the following year. Most perennials have herbaceous stems, but a few have woody stems.

Landscape beds are usually mixed plantings incorporating annuals, perennials, shrubs and trees. Shrubs and trees provide the “backbone” of the landscape as well as winter interest, while annuals are used as year-round complementary color. In general, there are three types of perennial beds:

• Island bed: A freestanding garden, often raised to promote drainage, to be viewed from all sides

• Perennial border: Double or single border with a backdrop of a wall, fence or woody shrubs that is generally viewed from one side

• Naturalized area: Established in an area of native plants like a woodland garden or natural stream

Planning is the key to success when designing and installing a perennial bed. Know the plant’s requirements for sun or shade, food and moisture. One of the most common pitfalls is placing shade-loving perennials in afternoon sun, or sun-loving perennials where they get less than six hours of sun.

When designing large perennial beds that are to be viewed from a distance or by passing vehicles, a simple theme, both in color and species, is most suitable. In smaller beds, or beds close to where you walk or sit, it’s nice to have more variety with many colors and textures. Plan a continuous bloom sequence for year-round interest.

Know the habit and final size of the perennial to prevent a vigorous plant overtaking less vigorous specimens. Spacing perennials is critical as many start small and grow large in width and height. Space plants according to their mature size (the size they will achieve in the third year of growth). Pay close attention to the botanical name, or pedigree, which tells you how the plant will grow.

When to plant

You can plant perennials any time, however early fall is the ideal planting time, because new plants have a chance to develop a healthy root system during the fall, winter and spring, before summer’s heat stress. A well-developed root system will be better able to withstand dry periods and summer heat.

Preparing perennial beds

Make a trench three inches deep around the perimeter of you bed, remove or cover any plants you want to remain, and spray the entire bed with non-selective weed Killer. Glyphosate (Roundup or Kleenup) kills most grasses and weeds, however you may need special herbicides to kill established ivy, nutgrass, clovers, or onions. Wait until everything is completely dead before tilling, then spread peat moss or mushroom compost and till as deeply as you can.

Using mushroom compost or peat moss will break up clay, encourage roots to spread quickly, and help the bed retain moisture longer. Make sure any compost or soil amendment you

add is sterile (no diseases or weed seeds). Pull the tilled soil away from the bed edges to allow for the thickness of your mulch.

Choosing the right perennials

The perennial plant trade offers more than 3,600 species and cultivated varieties, and more are added each year. With so many choices, how do you pick the right plants? Here are three simple rules:

• Stick to varieties that are known to do well in your area

• Match the ideal growing requirements; plant the “right plant in the right place”

• Devote some time to maintenance; food & water, mid-summer trimming, regular deadheading.

You don’t have to plant 50 species in one landscape, or always use the latest and most fashionable cultivars – you can make a stunning display with five varieties that have proven reliable over many years. Pay attention to new hybrids that have improved tolerance to shade/sun, fewer pest problems, require less water and pruning, and have an extended flowering time. Make sure the plants you choose are hardy for our climate zone (6 or 6a).

Rainfall and drainage are a very important factor in plant survival. Inadequate drainage in clay soils creates favorable conditions for root rots, and dry soils cause plant stress from drought. In fact, more perennials die from wet winter soils than from cold. This is why raised beds, terracing and adding peat moss are so beneficial.

Feeding perennials

The most effective way to feed is to mix with the soil when planting, and then scatter it on the ground around the plant in later years. Use a well-rounded multi-vitamin/multi-mineral plant food like Espoma Plant Tone. Perennials need food early in spring or summer, when they put on growth, and not so much the remainder of the year. Unless the soil temperature is warm, plants don’t absorb food through their roots. If you cut back perennials midseason, you should feed them again.

Steve Boehme is a landscape designer/installer specializing in landscape “makeovers.” “Let’s Grow” is published weekly; column archives are online at For more information call GoodSeed Farm Landscapes at (937) 587-7021.

No posts to display