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Sonia Uyterhoeven is the Gardener for Public Education at the New York Botanical Gardens. She will be contributing to these pages on a regular basis.
There is nothing inherently complex about hostas. They are easy-to-grow, readily available, adaptable foliage plants for the shade garden. The problem with hostas is that they have a predisposition toward mutation, and there is a glut of similar looking cultivars on the market.
Hostas come from Japan, China, and Korea. There are around 45 species of hosta with more than 7,000 cultivars. Two well-known species are the fragrant Chinese Hosta plantaginea and the waxy glaucous (blue) Japanese Hosta sieboldiana. They are parents to myriad successful cultivars on the market. Members of the plantaginea group tend to be heat lovers, while members of the sieboldiana group cannot take too much sun and warmth, as their waxy blue coating starts to melt and turn green.
Hostas are notorious for having split personalities, meaning they sometimes change color during the course of the season. There are terms for this type of color instability: A hosta that changes from yellow or white to green is called viridescence; a change from green to yellow is called lutescence; and from yellow to white albescence.
Often classified by size: dwarf, miniature, small, medium, large, or giant, hostas hate dry soil, so do not plant them directly under greedy trees such as Norway maples (Acer platanoides) or in dry areas. They prefer rich organic soil and good moisture. Before planting them, amend the soil with organic matter and add a light layer of organic mulch such as shredded leaves, which will help to continuously replenish the soil.
Hostas thrive in part shade and flourish with light morning sun. Afternoon sun is usually too hot, and the foliage tends to brown around the edges (this can sometimes be remedied with more moisture). As a general rule, green-leafed hostas require less sun, while variegated hostas need more sun. Variegated plants are unable to photosynthesize in the variegated areas, which lack chlorophyll. Thus they need more sunlight to make up for the decrease in photosynthetic surface area.
For hostas to shine as foliage plants, give them a boost by fertilizing once in spring and an optional second application in mid-summer. You can either let your hostas grow into large clumps or periodically (every four to five years) divide them into smaller plants.
The best time to divide a hosta is either in spring when the tips are emerging, or in August when the intense heat of the summer is beginning to subside. If you divide in August, you may want to cut off some of the larger leaves to prevent excessive water loss.
The largest concern for the hosta gardener is slugs; they have a preference for fragrant hostas and avoid thick-skinned varieties. The old fashion remedy is to place a saucer of beer in the garden to drown the slugs. Edging your prize hosta with either used coffee grounds (caffeinated) or with copper pennies also works, as does periodically sprinkling iron phosphate around your planting.
How do you handle your hostas? Let me know here.
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