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White Pine boughs make a good winter mulch for garden beds

Now that the holidays are over, in northern climates the ground is frozen. Now is the time to apply a winter mulch to keep the soil cold and insulate it from alternate freezing and thawing. The action of freezing and thawing, which occurs throughout the winter season, causes shallow-rooted and fall-planted perennials to be heaved out of the ground and roots to become desiccated. I find that members of the coral bells clan—heucheras, heucherellas, and tiarellas– are particularly prone to heaving.  

At this time of year there are plenty of evergreen boughs and discarded Christmas trees around, free for the taking (save those pennies for new plants). These are perfect to cut up and lay gently on frozen beds and borders. If there is still snow on the ground lay the boughs on top. I never got round to cleaning up all the fall leaves, but the evergreen boughs will prevent them from blowing all over the place. As the weather warms in spring gradually remove the boughs to allow new growth to occur.

This Norway spruce is in danger of losing a few branches

Having taken a walk around our neighborhood today after the first snowfall of the season, it is pitiful to see how some evergreens take such a beating with wet heavy snow. One’s instinct is to bash the snow off as soon as you can, but beating on an already stressed branch from above is trouble. Always brush snow off gently from below with a broom so that it falls away from the bush. This Norway spruce is in danger of losing a few branches.

Dwarf mounding evergreens, such as some Chamaecyparis and arborvitae tend to open up in the center under snow. Wearing garden gloves, protect them by winding soft twine round them from bottom to top, keeping the twine just tight enough for them to hold their shape. Snow then will fall off more easily. It is too late for this Tsuga occidentalis ‘Rheingold’.

It is too late for this Tsuga occidentalis ‘Rheingold’

This year it was Thanksgiving weekend before I had a chance to start tidying up in my garden. I’m not exactly a “neatnik” but I do like it to look nice and garden hygiene is important too. Be careful to clean up any dropped leaves beneath roses for fear of spreading black spot spores when the spring rains come next year. The  spores overwinter in organic mulch (I like to remove the mulch) and will be splashed up onto new growth and re-infect the bushes. Spent annuals go on the compost pile, but there are a couple of schools of thought about cutting back perennials. Some like to cut everything down, cover the beds with a good layer of compost or shredded leaves, and head out of town for the winter. Those of us who stay put through the winter need a pleasing view all year.

Conservatory Garden, New York City

I took a walk in the Conservatory Garden in Central Park, New York City, to see how they handled the problem. Some cut and some left there as well. Ornamental grasses of course are dramatic against autumn leaves (purple smoke bush here with Miscanthus grass), and even more so in front of evergreens as the winter progresses. 

Others that I leave include rusty colored tall sedums such as ‘Autumn Joy’, ‘Garnet Brocade’ and ‘Frosty Morn’, purple coneflowers, black- and brown-eyed Susans, perennial sunflowers, Russian sage and all silvery-leaved shrubs (Caryopteris, butterfly bush, common sage etc.). Not only do these provide winter interest, they become popular feeding stations for resident birds that add so much to the winter garden.

Spore cases of ferns are also decorative, although some remove them for neatness. Here sensitive fern (Onoclea sensibilis) adds height and texture to a bed of Helleborus hybrids that will bloom next spring.  

Sensitive fern (Onoclea sensibilis) adds height and texture to a bed of Helleborus

In my garden, I leave the dried spore cases of ostrich fern (Matteuccia struthiopteris)  too under a canopy of Euonymus branches.