Perennials can add flower color and foliage texture to a landscape. They can be grown as border plants among foundation plantings or as stand-alone beds. Perennial, by definition, means to return year after year. A perennial garden, if planned correctly with adequate soil, light, water and plants that are naturally tough and well-adapted to conditions will bring many years of satisfaction with very little work.
Success with a perennial garden is all about planning and knowing the conditions of your planting site. Full sun or shade; wet or dry; windy or well-protected; these conditions all factor into what should be planted. There are perennials available for any environment, so when planning a garden, be sure to choose plants according to the specific climate of your site.
Soil is one of the key elements to consider when planting a perennial garden. Most perennials prefer a compost-rich, well-drained soil but many will adapt to different soil types. If you have heavy clay soil, you may have to create a raised bed to provide adequate drainage or add organic materials annually to your beds to amend the soil. Clay soils drain poorly and bind up nutrients, causing sensitive plants to rot.
At the opposite end of the soil spectrum is sand. Sandy soil leaches nutrients and water but is a bit easier to amend with a lot of organic material to beef up nutrient content and soil structure. If you are not sure what type of soil you have, squeeze it in your palm. If it remains in the shape of your palm, you have heavier soil. If it doesn’t maintain a shape, you have sandier soil. The bottom line is that the more organic matter you can add to your planting bed, the better off your perennials will be.
Light and water are another two key elements to any successful perennial garden. Full sun perennials require 6 or more hours of direct sunlight to flourish. Sun/part shade plants require about 4-6 hours and shade plants about 2-4 hours. If you plant a full sun perennial in a partially shaded area, it will probably still be alright but it won’t bloom and grow to its full potential. Don’t try to fight nature. If your garden site is in a shady area, plant shade plants. You can always add annuals for more flower color if needed.
Perennials that are freshly planted will require supplemental water during the first growing season and any drought periods in subsequent years. Water in the morning so that the plant has the entire day to use the water and the roots will be less likely to rot. Once the plants are established they will need very little supplemental water. This can be a good reason to plant perennials rather than annuals.
When choosing what to plant, consider growth habits, flower color, foliage texture/color, bloom times and regional hardiness. It is well worth the time to map out what you are planting to get a feel for how much room (height/width) mature plants will need. Planting in odd numbers, drifts and repeating colors/plant types will help to define the garden and give it a finished look. If there are too many different plants in a bed, it becomes chaotic, messy and may not ultimately be as low-maintenance as desired.
Very few perennials bloom all spring, summer and fall, which is why foliage is also very important for looks. Foliage can be utilized as much for garden color as blooms can, but be careful that there isn’t too much color variety. You want your variegated plants, in a design sense, to stand out in contrast to your green plants. Foliage texture can be used very much the same way. Placing fine foliage such as a fern next to bold, large foliage such as a hosta will accentuate the individual attributes of each plant.
Choose plants with varying bloom times so that there will always be something blooming in your garden. You certainly want to ensure that a few groups of your plants are blooming in the spring, and that the colors go together. When the spring bloomers are finished, you’ll want another group to start blooming and so forth. A well-planned garden will always have complimentary plants blooming and taking up where others left off. See the chart below for bloom times.
One of the most important things to consider with plant selection is the hardiness zone. In New England, you want to select plants in the USDA Plant Hardiness Zones 5, 6 (-10 to -20, & 0 to -10 degrees) and under. Lower zones indicate colder climates. Any plant higher than a zone 6 can be treated as an annual in this area.
Maintenance during the growing season consists of periodic weeding, removal of spent blossoms (deadheading), staking (if necessary) and pest control. Spring cleanup consists of cutting back or raking up old foliage, spreading new compost or mulch, splitting any summer blooming plants and adding any required slow-release fertilizers. Fall cleanups are similar to spring; trimming where it’s needed, splitting spring bloomers and adding winter protection for tender plants.
After three to five growing seasons, some perennials may need to be divided to prevent overcrowding. Overcrowded perennials often bloom poorly or not at all. Spring and early-summer blooming perennials are usually divided in the fall (mid-September through mid-October). Plants that flower in mid to late summer and fall should be divided in the spring before growth begins. Some perennials have specific times for splitting. It is best to check if you are not sure before lifting the plants. Here are some basic steps for splitting:
- Use a spade, shovel or fork to dig around and under the plant and lift it out of the soil
- Remove most of the soil from the roots by hand or with a hose
- Use pruning shears or a sharp knife to cut apart the healthiest part of the plant, often on the outside. Most clumps can be divided into four or five smaller clumps after dead and discolored parts are removed
- Replant divisions as soon as possible after amending the soil. Protect with mulch (2- to 3-inch depth) in late summer and fall. Water as necessary
Perennial Bloom Times
Wild Ginger Asarum
Pinks, various species
Lilies of the Valley
Early Spring Bulbs
Mid-season Spring Bulbs
Late Spring Bulbs
Fern Leaf Bleeding Heart
‘Early Sunrise’ Coreopsis
Stella D’Oro Daylilies
Bearded and Siberian Irises
Fern Leaf Bleeding Heart
Asters some varieties
Joe Pye Weed
Tulips, Lily Flowering