Gardening with Perennials

Written by Barbara Gee

Gardeners in southern New England live with truly erratic weather! Take last year, for instance – the spring was long and wet, the summer was kind of blah, and the winter was just plain weird – my cherry tree was trying to bloom on Christmas Day! Even the experts were not sure what this would mean for the spring this year. 

Planting perennials is one way of dealing with the questionable aspects of weather. But this does not mean that “perennial” is synonymous with “easy.” It can be if you choose the right perennials. But just because an established perennial plant survives for many years does not mean that it can do so without assistance. 

Perennials produce seeds and blossoms more than once in their life span. A perennial comes back year after year – in the right conditions. You have to give your perennials the conditions they want or they will not be happy. A plant like Mandevilla, for instance, that gorgeous vine with electric pink blossoms, is perennial in its native land of Brazil but behaves more like an annual in Rhode Island. The winter is too harsh for it and the plant dies, unless brought inside and overwintered. 

Perennials are classified as either herbaceous which means they have soft stems and tops which die back to the ground in the fall, like Bleeding heart (Dicentra), or woody which means they have stiff, shrub-like stems, like Russian sage (Perovskia). 

Perennials are also defined as hardy, semi-hardy or tender depending on their ability to survive the winters here. Hardy perennials, such as bellflower (Campanula), need very little protection through the winter; half-hardy or semi-hardy perennials need some protection, such as mulch; and tender perennials like salvia’s do not survive the winters. Tender perennials, often tubers such as dahlia’s, can be left to die or dug up and stored through the winter to be replanted in the spring. 

Perennials in the Garden
“Perennial borders” often contain a mix of shrubs and annuals because very few perennials bloom all through the spring, summer and fall. Plant form, structure, and foliage are just as important as flower color. When choosing perennials go for ones that have beautiful foliage so that when they are not in bloom they still look good. If you use plants that loose their foliage even while still blooming, like ornamental onion (Allium), plant something like Lady’s mantle (alchemilla) that will come fast behind and cover up the spent foliage. But if you love color through the seasons then choose perennials that bloom at different times.

Perennials for Sun or Shade?
Plants have different needs – give them what they want. Some, like nicotine plant(nicotiana), need full-sun, which is 6-8 hours of sun a day. Others like partial sun or shade. Cimicifuga, hostas, ginger, ferns… love the shade.  

 Island Beds or Straight Borders
Traditionally perennial borders are placed against a backdrop such as a wall or hedge. These are designed to be seen from the front. But island beds have become more popular in recent years. They are free-standing and designed to be seen in the round, from all sides. Front-viewed borders usually have taller plants at the back, gradating down in size to the low plants in the front. Island beds require the height to be in the center but it can also be a garden structure such as a teepee.

Plant in groupings of three or five and continue the groupings along the border to give a cohesive look. 

Most people think only of annuals in containers but don’t pass up the opportunity of putting perennials in containers. You will probably have to bring it in to overwinter, but if the foliage and structure are great then it may be worth it. Bergenia, for instance, looks great in a pot. The wonderful leaves and red stems continue to look good even when its pink flowers have gone by. 

Buying Perennials
A perennial is a plant that should be around for a good number of years so buy strong, healthy plants from a reputable nursery. Check the plant to make sure there are no signs of disease, or lack of care. You can always shake a plant gently out of its pot to make sure the roots are healthy. 

Take note of the size the plant will become at maturity, and plan accordingly. 

If friends offer you a plant from their garden don’t take it just to be nice. Make sure it is something you want and not a plant that will take over your garden.

Perennial Care
Healthy soil will ensure a healthy plant. Care for your soil and the plant will take care of itself, pretty much. If your soil needs amending add organic material, like compost, when preparing the bed. Fall is a good time to do this – the amendments will have time to settle in before you plant in the spring. 

Plant in a hole that is big enough to accept the spread of the plant’s roots. Add a little fertilizer to give the plant a boost of nutrients and plant the crown of the plant at soil level. Then water. Keep watering regularly for the first week or two, after which you can ease off and establish a regular watering routine. It’s helpful to cut or pinch back a plant with heavy top growth so that its energy goes into the roots rather than the foliage. Perennials don’t necessarily look great when they’re first planted. They grow to look better the second year and get better after that.

In general, the best time to transplant a perennial is after it has finished blooming, either in the spring or the fall. Don’t transplant too late into the fall or the plant may not have time to settle into its new home before the cold of winter hits.

Garden Maintenance
Plants need water either from you or nature so make sure they are getting it. The other tasks include deadheading, pinching, pruning and cutting back. These all make the plant look nicer and help it put energy into root growth and new bushy upper growth. You may need to stake tall plants like boltonia.

Keep the garden weed free – they compete for everything – nutrients, water, air, space. 

A late-fall cleanup of the garden makes it look tidy and makes less work in the spring. Removing debris ensures a clean garden which cuts down on conditions conducive to pests and diseases.

Keep records of what you planted when, and where.

There is nothing more fun than seeing perennials peek through in the spring. You feel the garden come alive. There may be sad moments when your favorite dianthus doesn’t appear, but then you see your new cranesbill (Geranium) beginning to show. Perennials just keep on giving if you treat them right.

Great Perennials for Rhode Island
Daffodil (Narcissus), yellow

Candytuft (Iberis sempervirens), white

Bleeding heart (Dicentra spectabilis), deep pink

Lady’s mantle (Alchemilla mollis), chartreuse and green

Ornamental onion (Allium aflatunense), purple           

Cornflower (Centaurea), blue

Catnip (Nepeta mussini), lavender and gray

Meadow sage (Salvia x superba), blue

Queen-of-the-prairie (Filipendula rubra), lavender

Snakeroot (Eupatorium rugosum), white