Yard and Garden: Selecting and Planting Perennials in Spring

Perennials can help keep a garden interesting all season

Perennials are a great way to provide flowers and color in the garden and by planting perennials with different seasons of bloom, you can have interest throughout the growing season. In this article, horticulturists with Iowa State University Extension and Outreach provide tips for selecting and planting perennials in your Iowa garden.

What should I look for when purchasing perennials?
It is important to select perennials well-suited for the planting location. Be sure the soil moisture, light levels and winter hardiness of the garden site match the growing requirements of the perennial. Additionally, check the mature height and width of the perennial and be sure there is enough space for the plant to reach full size.

Select high-quality plants by first looking at the condition of the plant. The overall habit or shape of the plant should be well-balanced and not too big or small for the container. Perennials should be sturdy, robust and compact. Bigger is not necessarily better, as spindly or lanky plants do not transplant well. Leaves should not be off-colored or mottled. While a few brown leaf edges or missing leaves can be expected from a perennial growing in a container, avoid plants with excessive leaf damage or loss. Plants with overly dry or wet soil often indicate poor care and should be avoided. Plants should be firm and upright, not limp or wilted. Look under the leaves and near the crown of the plants for signs or symptoms of disease and insect pests. Do not purchase plants that show signs of insects or disease.

Remember, while flowers are pretty, they are not required for the purchase of your plants. Buying only plants that are in bloom often creates garden spaces with heavy spring bloom and little interest later in the season because many gardeners do most of their plant shopping in spring. Pretty flowers are nice, but are not a universal sign of good health and high quality.

How do I plant perennials?
Planting container-grown perennials starts with digging a hole at least twice as wide as the container. The depth of the hole should equal the depth of the soil in the container. It is important not to plant perennials too deeply as it may cause poor growth or flowering. Pull the perennial out of the container by squeezing the sides of the pot and then gently pulling the root ball out. Carefully loosen the root ball and roots, especially those roots that are circling the root ball. Set the perennial in the ground at the same level as in the container and backfill with the soil that came out of the hole. If the soil is of very low quality, such as those that are poorly drained or have a lot of clay, the planting hole should be dug three or four times the container’s width and the native soil can be amended with compost. In nearly all cases, amendments are unnecessary, and the soil dug out of the planting hole goes back into the hole.

Most perennials don’t need a starter fertilizer, but you can use one if you choose by following the label directions. Place 3 to 4 inches of mulch around the base of the perennial to help conserve soil moisture and prevent weed growth. The last step is to water the newly planted perennial. Watering after planting is important because it settles the soil and gets the roots in contact with the surrounding soil getting the plant off to a good start.

What are some good low-maintenance perennials?
All perennials require some maintenance. Watering, fertilizing, pinching, staking, deadheading, dividing and providing winter protection are common maintenance chores. Some perennials require frequent attention throughout the growing season. Others require minimal care.

Low-maintenance perennials for sunny locations include butterfly weed (Asclepias tuberosa), false blue indigo (Baptisia australis), hardy geranium (Geranium spp.), false sunflower (Heliopsis helianthoides), daylily (Hemerocallis spp.), Siberian iris (Iris sibirica), blazing star (Liatris spp.), daffodil (Narcissus spp.), peony (Paeonia hybrids), Russian sage (Salvia yangii, syn. Perovskia atriplicifolia), moss phlox (Phlox subulata), balloon flower (Platycodon grandiflorus), coneflower (Echinacea spp.), perennial salvia (Salvia x superba), sedum (Sedum spp.), speedwell (Veronica spp.) and ornamental grasses (various species).

Low-maintenance perennials for partial to heavy shade include lady’s mantle (Alchemilla mollis), Canadian wild ginger (Asarum canadense), heartleaf brunnera (Brunnera macrophylla), turtlehead (Chelone spp.), bleeding heart (Lamprocapnos spectabilis and Dicentra spp.), barrenwort (Epimedium spp.), hosta (Hosta spp.), creeping phlox (Phlox stolonifera), lungwort (Pulmonaria spp.), bloodroot (Sanguinaria canadensis), foam flower (Tiarella spp.) and ferns (various species).

Which perennials are long-lived?
Perennials are any plant that lives in the garden for three or more years. Some perennials grow well for a few years and then decline and fade away. When given favorable growing conditions and good care, long-lived perennials often thrive for 20 or more years. Long-lived perennials make great low-maintenance additions to the garden because they rarely need to be replaced.

Long-lived perennials include black snakeroot (Actaea racemosa), lady’s mantle (Alchemilla mollis), goat’s beard (Aruncus dioicus), butterfly weed (Asclepias tuberosa), false blue indigo (Baptisia australis), gas plant (Dictamnus albus), ferns (various species), hardy geranium (Geranium spp.), ornamental grasses (various species), daylily (Hemerocallis spp.), hosta (Hosta spp.), Siberian iris (Iris sibirica), blazing star (Liatris spp.), daffodil (Narcissus spp.), peony (Paeonia hybrids), balloon flower (Platycodon grandiflorus), lungwort (Pulmonaria spp.), black-eyed Susan (Rudbeckia fulgida), stonecrop (Sedum spp.) and Carolina lupine (Thermopsis villosa).