Gardening: Hellebores hardy enough to withstand deep freeze

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If 2013 was the year you planted "borderline hardy" perennials in your garden, you may be wondering if they will survive the Polar Vortex of 2014. Within the Pittsburgh metro area the USDA plant hardiness zones range from 5b (minimum temperatures of minus-10 to minus-15 degrees) north of Pittsburgh and in the mountains to our east, to 6a (minus-5 to minus-10 degrees) or 6b (0 to minus-5 degrees) in Allegheny County and the counties along its borders.

It was tempting to push the zonal boundaries after decades of winters with lows barely into single digits, but wise gardeners continued to rely upon tough, zone-appropriate plants as the mainstays in their gardens. One of the most reliable plants in our region is the Lenten rose (Helleborus orientalis), also called Helleborus x hybridus because of genetic mixing with other species. Hellebores are a tried-and-true perennial hardy in zones 4-8.

Hellebores' buds begin to emerge from the ground by mid-February, depending on the variety and the severity of winter weather. By mid-March, many are in full bloom and their flowers persist until mid-summer. The single, semi-double or fully double flowers can be found in shades of white, ivory, yellow, pink and purple. More unusual cultivars sport speckled or bi-colored petals. Hellebore flowers are subtle and best appreciated up close. Their natural habit is to nod downward, encouraging the gardener to bend down and appreciate the beauty of their markings. Newer cultivars have been selected for outward- or upward-facing flowers. To enjoy their unusual details, cut them close to the base of the flower and float them in a shallow bowl.

Hellebore foliage is a leathery and dark green, although cultivars with variegated foliage are available. The deeply divided leaves stand 12-18 inches high and are "semi-evergreen," meaning that their leaves persist through the winter. A planting of hellebores is beautiful when in bloom but has the added feature of great-looking, weed-smothering foliage through the growing season and some visual presence all winter.

Hellebores thrive in rich, moist, well-drained soil. They will tolerate a wide range of light conditions, from shade to sun. Failure is rare and usually attributable to planting them in wet, poorly drained locations. They are drought-tolerant once established, but a planting in full sun may need more water than in their preferred shady location. Hellebores do not require division and will form a large attractive colony if left to naturalize. In addition to their ease of culture and adaptability, hellebores are deer-resistant.

Newer cultivars of the Lenten rose are expensive but can be propagated by division, best accomplished in late summer or very early spring. Barry Glick of Sunshine Farm and Gardens in West Virginia recommends propagating a superior cultivar or an exceptional seed-produced plant by marking it when in flower and digging it up as soon as the ground thaws in early spring. Rinse the clump and make careful cuts with a steak knife, being sure to leave a couple buds on each division. He recommends using a transplant solution with B-1 and chelated iron, as well as a fertilizer with a high phosphorous content to ensure success.

If you want to spread this easy-care perennial throughout your garden or share them with gardening friends, allow the plants to set seed. You will notice that after a few months (yes months!) of bloom, the color of the flowers begins to fade, and the cream stamens transform into pale green seed capsules. Allow the flowers to senesce on the plant, then cut the stems to the ground. Look for tiny seedlings around the plants in late summer or early spring and carefully transplant when the first true leaves appear. Seedlings may take 3-4 years to flower, but pretty colonies of Lenten rose can be easily established throughout the garden using this technique. Hellebore flowers do not come true from seed, i.e. they are not identical to the plant they came from.

The only maintenance chore is to cut the old foliage away in late winter or early spring. Wait for a clear day in early February and cut back the entire plant to within a couple inches of the ground. At this point, there should not be any new growth. If you wait until new growth appears the chore is a bit more time-consuming, requiring selective cutting away of the old leaves. Small, needle-nosed garden scissors are ideal for this "close" gardening work and much easier than hand-held pruners.

Recommended cultivars

'Ivory Prince' -- Burgundy buds followed by outward-facing creamy flowers tinged with rosy pink. The flowers look great beneath the branches of a kousa dogwood or redbud tree.

'Metallic Blue Lady Strain' -- Dusky purple flowers contrast with cream stamens. It combines beautifully with the buttery yellow variety 'Heronswood Yellow.'

'HGC Pink Frost' -- Soft pink flowers that age to a purplish red.

'Cinnamon Snow' -- Cinnamon red flower stalks with white flowers that age to pink.

'Winter Jewels Golden Sunrise' -- Three-inch flowers in shades of yellow with red starburst.

Check with your local nursery for unusual hellebore cultivars or look for online sources. Hellebores are exceptionally long-lived perennials and are a great investment for any garden.

Pam Horvitz is a Penn State master gardener. Columns by master gardeners sometimes appear in place of the Garden Q&A by Sandy Feather, a Penn State Extension educator.

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