If you are a gardener that shops for plants that are perennial because you want to plant them once and have them forever, you may be wondering why some plants sold as perennials fail to return after a few years in a garden. You may blame a hard winter, the nursery that sold you the plants or bad luck for the plants death when in truth it may just have lived out its normal life span.
When gardeners begin to take an interest in plants as something other than decorating material they learn that plants have various lifespan categories, assigned by botanists as perennial, biannual (biennial) or annual. Annuals are those plants that live one season; they bloom and produce seed in their first year of life, then die. Biennials make some foliage growth in their first year, bloom the second year and then die. Perennials are plants that live more than two years.
The problem is that some perennial plants barely make it past the two year mark, and some of them are common garden plants. There are just some species of plants whose lifespan is short, even though they are classified as perennial. While they may give you a good show for a year or two they will need to replaced far more often than other types of garden plants. Gardeners need to be aware that not all perennial plants will last for a long time in the garden.
Culture and conditions contribute to plant longevity
While the normal lifespan is indeed a factor in how long a plant lives other things can also affect a plants lifespan. Plants that are at the edge of their tolerance range for cold or heat will probably live a shorter life than those that are in an ideal climate. Make sure to check the planting zone rating for the perennial you are considering. While most plant tags or descriptions will give you the cold tolerance rating very few list heat tolerance ratings for plants. A few nurseries now list heat tolerance but in general if you live in an area that gets very hot for long periods each summer you’ll want to look up heat tolerance ratings for non-native plants. Some plants won’t bloom without a certain number of cold days also. Tulips and daffodils are examples.
And don’t just check the zone for the species in general. Some cultivars or varieties of common garden plants may be less hardy than others. For example buddleias and lavender each have varieties that are quite hardy, surviving in Zones 5 or less, but they also have varieties that need warmer zones to thrive. Sometimes perennials or varieties of perennials that are not in the right zone will live for a year or two but then die when there is a colder winter or warmer, more humid summer.
Some climate factors other than temperature may have to be considered also. Plants who originate in regions that have dry winters may suffer and have a shorter life in wet snowy winter areas. Many plants that come from the Mediterranean areas, like rosemary, and some bulbs, like tulips, don’t like wet winters. Plants can also have varying tolerances for windy areas or long periods of drought.
When garden plants are hybrids of several species that have different lifespans in the wild or come from vastly different climates, some of those hybrids may have a shorter or longer life in the garden or perform better and last longer in some places than others. An example of this was the red coreopsis that was being offered several years ago. These hybrids rarely lasted more than the first season in the garden. It can take several years after a new hybrid of an old garden favorite is put on the market for its hardiness and longevity to be established.
Light requirements can be crucial to longevity too. If you plant a shade lover in full sun or vice versa you will probably shorten the plants lifespan. Soil type and soil pH ( acidity or alkalinity) are also factors. A plant that likes acidic soil for example, may survive in alkaline soil for a few years but it probably isn’t a healthy, happy plant and will be more susceptible to disease or insects or just disappearing from the garden. The old adage of right plant in the right place gives each plant the greatest potential to reach its normal lifespan.
How long a plant takes to reach maturity and how it handles competition from other plants may also affect its lifespan. In general a plant that is slow to reach maturity will live a long time when it does manage to reach that stage. But these plants may take a little extra care in getting them established or they will die out early. These plants will need to have more rampantly growing species around them kept from overtaking them or competing for light and water until they are large enough or well established enough to fend for themselves.
Plants that fool you
Sometimes plants that have been in your garden a long time are not the original plants you planted. But they are so successful in spreading or seeding themselves that the lifespan of the individual plant is less important. Hollyhocks for example are biannual plants, but they reseed so freely that once established in the garden you almost always have them. Plants that reseed freely such as comfrey and columbine may not have long lived individuals but persist in the garden. Even some annual plants may reseed and seem to be perennial in the garden.
In general plants that spread quickly through rhizomes or tillers (underground stems) are short lived individually but long lived as a species in the garden. Bearded iris put out new rhizomes each year but the old rhizomes die after blooming. A bed of irises may persist 50 years or more. Plants that produce “daughter” plants around the original plant and make large clumps of plants such as hosta, are also long lived, sometimes as individual plants or sometimes as a “family”.
Plants that have woody or semi-woody stems are also longer lived than plants that die to the ground each winter. Plants that remain evergreen (retain leaves) in the winter are generally longer lived than other types of plants.
So which plants live the longest in the garden?
When plants have everything they need to thrive and excellent care from you some will still live longer than others. There is a natural lifespan for each species, hamsters have shorter lifespans than dogs, coreopsis has a shorter lifespan than hosta. A perennial is considered short lived if it lives 2 to 4 years on average. It is medium in lifespan if it lives 5 to 8 years and long lived if it lives on average 9 years or more. Some plants, like peonies, may live longer than 50 years if they are in the right spot.
Long lived perennials ( averages more than 8 years in the right conditions)
These lists are for non-woody perennials.
- Acanthus mollis- (Bears Breeches)
- Aconitum spp.(Monkshood )
- Alchemilla mollis (Lady's Mantle )
- Amsonia orientalis(Blue Star)
- Anaphalis triplinervis (Pearly Everlasting)
- Aruncus dioicus (Goatsbeard )
- Asclepias tuberosa (Butterfly Weed )
- Baptisia australis (False Blue Indigo)
- Centaurea montana
- Chelone oblique- Turtleshead)
- Cimicifuga racemosa (Snakeroot)
- Crosmia spp.
- Dictamnus albus (Gas Plant)
- Ferns (various species)
- Filipendula rubra ( Meadowsweet)
- Geranium spp.(Hardy Geraniums)
- Helleborus spp.( Hellebore)
- Helenium autumnale ( Sneezeweed)
- Hemerocallis spp (Daylily)
- Hosta spp
- Iris sibirica (Siberian Iris)
- Liatris spp (Blazing Star)
- Lunaria rediviva (Money Plant, Honesty)
- Narcissus spp (Daffodil, narcissus)
- Nepata x faasenii ( Cat mint)
- Ornamental Grasses (most perennial species)
- Paeonia spp (Peony)
- Papaver orientale ( Oriental poppy)
- Platycodon grandiflorus (Balloon Flower)
- Pulmonaria spp (Lungwort)
- Rudbeckia fulgida (Black-eyed Susan)
- Sedum spp ( Stonecrop )
- Veronicastrum virginicum ( Culvers Root)
Short lived perennials (3-5 years)
- Aquilegia spp (Columbine )
- Coreopsis grandiflora (Tickseed)
- Delphinium spp (Delphinium )
- Dianthus spp (Pinks)
- Echinacea spp.( Coneflowers)
- Gaillardia x grandiflora (Blanket Flower)
- Gypsophila paniculata (Baby's Breath)
- Heuchera spp (Coral Bells )
- Hyacinthus orientalis (Hyacinth )
- Leucanthemum spp.(Shasta Daisy)
- Linum perenne (Perennial Flax )
- Lupinus hybrids (Lupine )
- Lychnis chalcedonica (Maltese Cross )
- Monarda spp. (Bee Balm)
- Papaver nudicaule (Iceland Poppy)
- Scabiosa spp.(Pincushion Flower )
- Tanacetum coccineum (Painted Daisy )
- Tulipa spp (Hybrid Tulips )
You’ll notice that some popular garden plants are relatively short lived. (Some reseed or sucker though.) Remember this if you are spending large sums of money on a new variety of one of these species. Some common garden plants aren’t listed because they fall somewhere in between long and short lived or that they have so many varieties and hybrids with different life spans. Roses for example can be very long lived in some species and hybrids and short lived in others.
This doesn’t mean that you should avoid certain perennials, just that you will need to replant some varieties if you want the same display in your garden each year. Some short lived perennials are popular because they are great performers in the garden while they last.
Here are some additional articles by the author you may want to read.
How to Divide Bearded Iris
How to store summer bulbs through the winter
Do you have poisonous plants in your garden?
To contact the author or sign up for her weekly garden newsletter please write her at firstname.lastname@example.org You can get a shorter version of the weekly newsletter by reading the authors blog at http://gardeninggrannysgardenpages.blogspot.com