The pink lady’s slipper may be the state flower of Minnesota, but if there was ever a popularity poll for perennials, the hosta would surely prevail. Reliable and hardy with countless combinations of leaf color, shape, and texture, hostas have won the hearts of northern gardeners with their fabulous foliage.
Hostas are herbaceous perennials, hardy to Zones 3 or 4, depending on the variety. Sometimes referred to as the plantain lily, hostas have fleshy roots and short spreading rhizomes; in spring broad leaves emerge from a central crown and develop into a mounded form. Leaves come in colors from bright green to gold and even blue tones; variegation can result in an edging or center of white, cream or gold; or splashes of color. Leaf texture varies and can be smooth, veined, or even puckered. Leaf size ranges from petite (few inches long) to gigantic (few feet long). Descriptions such as heart-shaped, lance-like, and cupped characterize different leaf shapes. Depending on growing conditions and variety, individual plants range in size from six inches high and a foot or less across to 3-4 feet high and 5-6 feet across.
Although hosta flowers are sometimes discounted as secondary, they can provide great ornamental value. The flower stalks, known as racemes, hold bell-like blossoms of white or lavender to blue. Some flowers are exceptionally fragrant as well as attractive to hummingbirds and bees.
While hostas are often referred to as shade-loving plants, too dark a location will lead to slower growth rates and compromised performance. Hostas can survive in deep shade, defined as 4 hours or less of sun, but really thrive in sites where filtered or dappled shade is available for much of the day.
Some hostas exhibit color variability, changing color according to the amount and intensity of light exposure. Yellow and gold hostas will actually benefit from 2-3 hours of morning sun, helping to develop richer leaf color. Blue hostas have a waxy coating on their leaves, much like the needles on blue spruce, and require a shadier site to avoid leaf burn and bleaching from intense sunlight. As this coating washes off with rain, the plant becomes more vulnerable to sun damage as the growing season progresses. Brown, scorched leaf surfaces or leaf tips on a hosta is a symptom of sunscald. This can be alleviated by moving the plant to a shadier location or providing more water.
For sunnier sites, plants in the Hosta plantaginea group will fare better, and actually develop more of the fragrant flowers they are known for; ‘August Moon’, ‘Sum and Substance’, ‘Honeybells’ are in this category. Hosta breeders continue to develop new varieties with greater sun tolerance; ‘Sundance’ and ‘Sun Glow’ fit into this category. At the same time these hostas will still tolerate shade, giving gardeners greater flexibility in site location.
Hostas prefer rich, moist soil that is high in organic matter, yet well drained. Having a soil test done prior to planting can be valuable in understanding soil condition and providing recommendations of what amendments can be added to obtain the optimum nutrient levels and pH range. Adding organic materials such as peat, composted manure, or leaves will help improve soil structure and tilth. That said, hostas are generally adaptable and survive in a wide range of soils, adding to their ease of growing and popularity.
Native to Japan, China, and Korea, hostas were imported first to Europe and later arrived in America in the mid 1800’s. There are hundreds of species and thousands of cultivars from which to choose. Besides ornamental attributes, gardeners should choose cultivars based on available light and space. Purchase plants from a reputable nursery, whether in person or online, checking to make sure they are free of obvious symptoms of virus, such as yellow or spotted foliage, dwarf, irregular or disfigured leaves, and other diseases. Some nurseries certify their stock as free of certain viruses.
Although hostas can be planted throughout the growing season, spring is generally the best time to plant. Hostas planted later when temperatures have warmed will need more water until their root systems have become established.
It is more affordable to purchase hostas as dormant, bare root divisions in the spring. Plant bare root plants with the crown (the root-shoot junction) even with the surrounding soil and the growing tips visible at the soil surface. Potted plants can be obtained throughout the growing season and should generally be planted at the same soil level as in the pot. Gently firm soil around the plant and water it in.
Hostas require an adequate supply of water to thrive. Hosta leaves have a large surface area and transpire or lose water easily. Consistent, even moisture equivalent to an inch of water per week is considered best for hostas. Deeper watering done with less frequency is better than frequent shallow applications that do not penetrate the root zone.
Hostas planted in dry shade will need attentive watering; rain does not always reach under eaves of buildings or through tree canopies in sufficient amounts. Planting hostas beneath shallow-rooted trees, such as maples (as pictured) or spruce will require watering for establishment and frequently thereafter due to excessive competition for moisture. Hostas in sunny locations will also need additional water to compensate for hotter conditions and increased transpiration.
Organic mulches, such as shredded bark, shredded leaves, or pine needles, will help to conserve and retain the moisture needed for hostas to succeed. Apply mulch after the soil warms in late spring to early summer to maintain a 2-4 inch layer, taking care to keep it away from the plant’s central crown. In addition the mulch will help to suppress weed growth, keep soil temperature even, and eventually decompose releasing nutrients into the soil.
Hostas can be fertilized with a basic garden fertilizer, however nutrients other than nitrogen optimally should be applied only if a soil test indicates they are deficient. Different formulations of fertilizer (most often granular or water soluble) are available and it is important to read and follow the instructions for rates and frequency of application. Some fertilizers are slow release, while others are faster release. A general garden granular fertilizer (often 10-10-10) is commonly found in the garden center and typically contains quick release forms of nitrogen. If a soil test indicates fertilizer is needed and one chooses a general garden granular fertilizer, it is recommended to apply it twice during the season for optimum growth: in spring as leaves emerge from the ground and once more before flowering. It should be noted that as communities regulate fertilizer for excessive phosphorous run-off, the analysis on some fertilizers may not contain phosphorous and may read 10-0-10, reflecting this change. It is always important to read label instructions before applying any fertilizer product. For more information on fertilization please see Soil Test Interpretations and Fertilizer Management for Lawns, Turf, Gardens, and Landscape Plants.
Keep fertilizer granules off leaves and from getting stuck between leaves near the crown to avoid burn. Water soluble fertilizers are easy to apply but need more frequent application. Although nutrients are released more slowly, organic fertilizers such as blood meal, bone meal, composted manure, and fish emulsion can be used, increasing organic matter in soil as well.
Discontinue fertilizing after the end of July as this may force active growth later than desired in the season and interfere with the plant’s ability to harden off and prepare for winter.
Common problems of hostas include slugs and deer. Less common problems can include variegated cut worm, viruses, earwigs, crown rot, foliar nematodes, leaf spots, mice, and voles. For assistance in diagnosing unknown problems visit ‘What’s wrong with my plant?’.
Weeds compete for water and nutrients, as well as detract from a well-maintained garden. However, gardeners will find that the broad leaves of hosta help to cover the soil and suppress weed growth with their shade.
Deadheading can be done at different stages according to the desired affect; some gardeners trim off hosta flowers before they mature so not to distract from the foliage display. Others wait until the blooms have died then cut the stalk off down to the crown of the plant. Leaving the flower to set seed can defer energy at the expense of leaf or root development.
Pruning is unnecessary during the growing season other than trimming off yellowed or hail damaged leaves or spent flowers for a tidier appearance. Raking up and composting or disposing of dead leaves as the plant enters dormancy helps to reduce build up of disease and insect pests.
Mature hostas may be divided, however it is not necessary for the health of the plant. Making more hostas is the usual motivation. In spring as the ‘eyes’ or growing tips start to emerge from the ground, dig up the clump and divide into sections with a sharp shovel or knife. In smaller plants or sections, it may be possible to gently pull apart the plants, leaving as much of the root attached to each crown or plant. Because hostas have fleshy roots, they hold moisture and nutrients which help the new divisions become established. Plant these new hostas, spacing them considering their mature size.
Hostas can be divided later in the season, although more damage will likely show for the remainder of the season. New transplants will need special attention with watering until established.
Hail damage is heartbreaking for hosta gardeners. Fortunately most hostas will recover in time. Early in the season remove the shredded leaves, water if necessary, and wait for new growth. Later in the season it may be necessary to live with some ragged leaves until new growth appears the following season.
Winter protection is generally not necessary for hostas. A standard layer of organic mulch already present during the growing season will help insulate the soil and prevent cycles of freezing and thawing. Providing some extra mulch for winter protection can be helpful, especially for plants transplanted late in the season. If diseases have been an issue, cut off infected leaves in the fall and discard them. When applying mulch in the fall wait until the ground has frozen to about 3 inches. Remove excess mulch in the spring as weather warms making sure it is away from the crown of the plants to avoid crown rot.
Hosta societies and grower associations are great resources for more information on hostas including the American Hosta Society and The American Hosta Growers Association. The American Hosta Growers Association has selected a hosta of the year each year since 1996. The choice is made based on the cultivar having consistently good performance across the US and that it is widely available.
Hosta of the Year winners:
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