Refreshing that perennial bed

Short-lived perennials

When you plant a perennial it is with a sense of a job well done and taken care of. We often don’t realize that some perennials are just plain short-lived. One reason for this is that many of the short livers readily self-sow giving us the illusion that they have long lives when in reality it is their offspring that come back year after year.

Take many types of delphiniums, which may live three or four years but are generous self-sowers. The same is true of lupines and columbines, gaillardia and rudbeckia. Shasta daisies, coreopsis and even perennial flax will gradually disappear unless they are refreshed from time to time.

Also on the list of short livers are biennials, including hollyhocks and sweet William. These plants, too, will tend to self sow and many therefore appear to be perennials but are, in fact, biennials that take two years to flower, then die. This leads to their tendency to produce copious numbers of seeds.

Often, many of these ephemeral plants simply live their brief lives and then pass from the garden. If you want to keep their presence, it’s a good idea to let them go to seed and even to replace them every couple of years so that you won’t have a big hole in the garden when their time is up.

Longer-lived perennials may seem to be the answer to low maintenance prayers, but some of these plants may demand division every few years. Exceptions to this would be the really long livers such as peonies, which seldom require division, and hostas. The gas plant, Dictamnus alba, is another great plant to leave undisturbed for a long time. It has a clumping habit that slowly expands and each year makes it more spectacular.

Shady characters

Bergenia, commonly known as pigsqueak, is a wonderful shade perennial that blooms early in springtime, sending up fat stalks of pink or white flowers. Its leaves are big, paddle-shaped and shiny, offering a very good contrast to hosta and the feathery foliage of astilbe or ferns. A big patch of bergenia can make you look like a real pro in the garden. And speaking of ferns, native ferns will fill in a shady space and act as a great backdrop for smaller plants. They do travel, but slowly.

Pulmonaria is beautiful in the shade garden. The spotted leaves stand out very well and you have the added bonus of colour – pink, white and blue – in springtime. When the flowers fade be sure to pull the stalk they were blooming on right out or you will have a ratty looking plant as the leaves on the flowering stem die back and turn brown.

Brunnera, with its silver and mint, heart-shaped foliage, has a stunning variety called ‘Silver Heart‘. The foliage is more silver than green and the plant lights up the garden.

The many varieties of Ligularia will light up the shade garden in August. ‘The Rocket’ has tall spikes of sunny yellow and ‘Desdemona’, has ray-like golden blooms with lovely round foliage that has red undersides.

What to do about lilies 

While you are refreshing your perennials, it might be a good time to start thinking about how to replace the lilies in your garden, assuming the red lily leaf beetles hasn’t already done them all in. 

One option is Hemerocallis or daylilies, which are impervious to the beetle. While nothing will ever take the place of your lilies, carefully chosen Hemerocallis hybrids can extend the blooming period and add a lot of summer colour to the garden. ‘Sunday Gloves’ have pretty white flowers, with slender, ruffled petals and is a rebloomer. Daylilies are one of the most reliable plants that include yellow blossoms.

They will also go after the native tiger lily and, if hungry enough, the little red devils will go after hosta and even Solomon’s seal. 

For late summer colour, there is always Echinacea which now comes in almost every hue except blue: what used to be called the purple coneflower now offers a wide range of yellows, melons, corals, oranges and pinks. You need to plant several to have a real show and they don’t multiply the way your lilies did.

The sunny garden

For the sunny gardens, phlox, which can add just about as much colour as lilies, although not in yellows, is another option. My favourite is the white ‘David’. It is of medium height – about 30 inches – and mildew resistant. Many people are turning to the new varieties that feature a darker eye in the same colour as the petal. Phlox blooms in August and the flowers last a long time.

Campanula varieties are reliable and reasonably long-lived and will self-sow. There are just so many to choose from. Everything from creeping bellflowers (avoid these rampant travelers if you have limited space) to well-behaved clumping plants with bell-shaped flowers in a range of heights. Colours are limited to blues and white.

For structure rather than colour, try some of the clumping grasses. Still a favourite is Karl Foerster feather reed grass, which looks fabulous in fall when everything else is fading. 

Ferns are another option. Native ferns will grow in both sun and shade although they demand moisture. They will soon create a grove of greenery. 

It’s worthwhile to check longevity when planning your perennial beds. Prepare for replacement from time to time.

(First published on July, 2023)