Perennial Flower Garden Basics
By: Julie Day
Ice Plant (Delosperma sp.) quickly spills over walls and ledges.
A well planned perennial garden offers a constantly changing variety of flowers for years to come, making it well worth the initial investment and work involved. Here are some basics for how to plan, plant, and care for perennials in your garden.
Types of Perennials
Perennials are ornamental landscape plants that live for more than two years. Unlike annuals (which live for only one growing season), or biennials (which live for only two growing seasons), perennials return year after year.
Perennials are lower maintenance and more tolerant than other types of plants. And because they grow over time, perennials offer constant surprises – spilling over walls, peeking out from behind other plants, and bursting into riots of color.
Perennials are classified according to their life cycle:
- Herbaceous perennials have soft green stems that die back to the ground in the winter. The roots remain alive, and the plant sprouts anew in the spring. Most often, when someone refers to “perennials,” they’re talking about herbaceous perennials. Hostas and coreopsis are herbaceous perennials.
- Woody (evergreen) perennials have harder stems that go dormant, but remain above ground, during the winter. Technically speaking, shrubs and trees are also woody perennials, but the term is mostly used to describe smaller ornamental plants. Rosemary and artemisia are woody perennials.
Perennials can also be grouped by their growth habits:
- Clumping perennials sprout stems from a central clump, also called a crown. The clump grows larger and larger each year, and it can be divided to make more plants.
- Spreading perennials send out new shoots from underground, creating new little plants all around the parent plant. They can be propagated simply by digging up and moving the baby plants.
- Single trunk perennials are a woody plant that grows from a single trunk, rather like a small shrub. They can’t be divided but are propagated by stem cuttings.
Chrysanthemums (Chrysanthemum sp.) are great fall bloomers.
How to Select Perennials for Your Garden
When shopping for perennials, be prepared to be overwhelmed by the choices! There are perennials for shade as well as sun. They may be tall or short, invasive or restrained, climbing or trailing. Most perennials have a specific bloom period, which may be in spring, summer, fall, or even winter. You’ll find every color of the rainbow and type of foliage. To choose the best perennials for your garden, you need to answer these questions:
- What is the hardiness and heat tolerance of the plant? I’ve seen many disappointed gardeners who purchased a plant they thought was a perennial, only to learn that it will only survive from year to year in warmer climates.
- How does the plant grow in your climate? Some plants stay green year round in warmer areas but die back in colder climates.
- Does the plant require full sun, part sun, or shade? And what are the conditions in your chosen location?
- What are the water, soil, and nutrient requirements of the plant?
- How large will the plant be at maturity?
- How much maintenance does the plant require?
- Is the plant an invasive spreader?
- When, and for how long, does the plant bloom?
Thankfully, most nursery plants have a tag that provides most of this information, which leaves you with the task of deciding which ones best fit the location you have in mind.
How to Design a Perennial Flower Garden
If you’re planning a perennial garden from scratch, keep in mind these design tips:
- Choose colors and textures that complement each other.
- Stagger bloom times for a longer season of color.
- Group plants according to their soil, water, and nutrient needs.
- For a more dramatic effect, group multiples of the same plant together.
- Allow room for the plant to reach its full size without crowding or shading other plants.
Bee Balm (Monarda sp.) is a tall spreading perennial that attracts butterflies.
How to Plant Perennials
Planting perennials is pretty easy, since the root balls are usually small and manageable, and the plants quickly settle into their new home. Spring and fall are the ideal planting seasons, but most gardeners plant perennials when they’re blooming, so they can see what you’re buying.
Follow these planting steps:
- Dig a hole twice the size of the root ball (or till up your new planting bed), and work in plenty of organic material.
- Gently remove the plant from the pot. Be careful – the stems are fragile!
- If the plant is root-bound, gently loosen or slice the roots a little before planting.
- Plant perennials at the same depth they were in the pot.
- Fill in around the plant with soil, and tamp down gently. Sprinkle in a little bone meal (or other source of phosphorus) in the fill dirt, to help the roots become established.
- Water well. Plan to water every few days for the first week, then at least once a week for 3-4 more weeks. If you’re planting in summer, you’ll need to water regularly until the weather cools.
- Add a 2”- 3” layer of mulch around the plants.
Daylilies (Hemerocallis sp.) are popular clumping perennials.
How to Care for Perennials
Many perennials are virtually carefree, requiring only a little attention to keep them blooming and in shape. Here are some tips for taking care of your perennials:
- Spread a little compost, or add a balanced organic slow-release fertilizer, after the last spring frost.
- Once the tops die back in fall, they can be cut back anytime before spring growth begins.
- Deadhead perennials to prolong the blooming season.
- Clip back leggy-looking perennials to keep them bushy and healthy.
- Taller plants, such as delphinium or peony, may need staking or other structures to keep them from falling over. For best results, put these in place before they’re needed to keep from damaging the plant.
- Many perennials benefit from being divided every few years, to give the roots a little breathing room. Fall and spring are the best times to divide perennials.
Black-Eyed Susans (Rudbeckia sp.) are popular choices for perennial gardens.