| Important other 'hardiness zones'
There are four basic plant zones that should be rated for hardiness: the roots, the stems, the leaves and the flower buds. Plant labels, however, rarely tell the gardener what part of the plant is hardy, let alone mentioning things like summer heat tolerance, soil moisture requirements and so on.
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Hydrangea arborescens
"White Dome"
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Roses, for example, may carry a designation of hardiness to Zone 5, but my English garden roses all succumbed to winter, leaving only the hardy rootstock. On the other hand, my Seven Sisters rose has never had 1 inch of dieback on its 20-foot stems.
And while my macrophylla hydrangeas have never died from winter, the flower buds certainly have.
We can use rose cones or burlap to wrap plants, but with our wild temperature fluctuations we run the risk of injuring buds and stems with too much heat. We can mulch to help prevent heaving and winter burning of roots. We can also water well to close up air spaces in the soil and even sprinkle fruit tree buds at night to coat them with protective ice before an April plunge.
Sometimes we will get a note in a catalogue that says this plant or that "blooms two weeks later than the species," offering us Northeastern Illinois gardeners hope against a spring freeze nipping the plant's buds. But in the end, we will learn which parts of any given plant are hardy through trial and error. Hopefully more of the former and less of the latter.
Cutting back ornamental grasses
 Part of the charm in growing ornamental grasses lies in their three seasons of interest. The bronze- and champagne-colored foliage can add lots of appeal to the winter landscape. The first snow, caught in those feathery seed heads, is exciting to gardeners who enjoy watching the seasons unfold.
But aren't you supposed to cut grasses back? Yes, just not yet.
Besides being beautiful, the foliage of ornamental grasses also protects their crowns from winter damage, so don't cut them back too soon. Waiting until the new foliage begins to emerge in the spring, though, can make the haircut difficult. April is probably the best time to perform this task. Cutting back your grasses before spring bloomers take center stage will prevent the awkward appearance of bleeding hearts or tulips set against a straggly brown backdrop.
One grass that you may want to cut a bit earlier is the Calamagrostis 'Karl Foerster' or 'Overdam.' These are cool season grasses (unlike miscanthus and pennesetum grasses that grow in warm weather) and the new growth begins earlier in April. Cut these back as soon as you see new green sprouts at their base to avoid cutting off any new growth along with the old.
An easy way to cut back grasses is to tie two strings around the sheaf of foliage--one near the base and one at the top--then shear across the base with electric hedge trimmers. Make the cut about 6 inches from the ground. The bundles can then be burned, bagged or composted.
Tying brown twine firmly around the base of your grass after Christmas will also help prevent outer stems from falling and blowing around the garden.
Grasses are heavy feeders and a shovel of compost or organic peat sprinkled over the cut crown will give the plants a spring boost. Watering them well after shearing will also prevent the exposed crown from drying out.
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December Events
Now–January 7, 2007 | Holiday Door Décor & More
Annual gallery exhibit of vintage and artistic doors adorned for the holidays by regional designers and artisans. These exhibits include fireplaces, benches and other design elements that offer dozens of decorating ideas and inspiration. 9 a.m.-4 p.m. daily. Admission $4.
Klehm Arboretum & Botanic Garden, 2701 Clifton Avenue, Rockford
815.965.8146 | www.klehm.org
December 9 - January 7, 2007 | Winter Flower and Train Show
Several model trains including an old-fashioned steam engine, freight train and trolley will wind their way through a tiny village set in a field of vibrant red, delicate pink and soft white poinsettias.
Lincoln Park Conservatory, 2400 N. Stockton Dr., Chicago
312.742.7736 | www.chicagoparkdistrict.com
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