Six on Saturday: Winter’s Air Fresheners

New daffodil leaves emerge among Arum italicum, Vinca, and native strawberry plants. Leaves still growing after late summer Lycoris bloomed have grown tall enough to spill over across the bed.

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During the winter months, after leaves have fallen and most herbaceous perennials have died back for the season, we still need an abundance of leaves to absorb and sequester carbon from the air.  Plants have the ability to absorb carbon based gasses and other pollutants and metabolize them to produce sugars and cellulose, powering their own continued growth.  Sweeping carbon out of the air is an effective strategy to combat the extreme warming which is changing our climate in surprising and expensive ways.

Each living leaf has tiny holes in its outer surface which allow it to breathe.  These holes, called stomata, breathe in carbon dioxide, carbon monoxide, nitrogen and methane and use these compounds in photosynthesis.  Pure oxygen and water vapor are exhaled by every leaf.  In this way, leaves ‘scrub’ and purify the air we breathe.  Indoor decorative plants purify the air in our offices and homes just as landscape plants purify the air in our larger community.

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Our need to scrub and sequester carbon based gasses doesn’t stop during the winter.  If anything, the need for a little help purifying the air increases.  And that is where evergreen plants can help.  Many of us include evergreen shrubs in our landscape for the structure they provide throughout the year.  Beyond aesthetics, living green plants continue their work of photosynthesis and growth through the winter.

Any plant in active growth helps to sequester carbon, including algae and turf grasses.  A great deal of research is underway to quantify how much carbon various plants can scrub from the air and store, annually.  Even as carbon can be stored in stems and leaves, so it, along with nitrogen, may be stored underground in the root system, which may be extensive and very deep.

So as gardeners, we ask ourselves what we can plant in our own gardens to absorb carbon when little else might be growing.  And the answers will depend on our own climate, needs, budget, skills and inclination.  While plant density remains important to protect the soil and to have the greatest effect, we can also remain aware of providing vertical density, through multiple layers of actively growing plant species.

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Mahonia aquifolium

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Evergreen trees like pines, cedars, other conifers, hollies and evergreen Magnolias not only sparkle and shine in winter sunlight, but also sweep many pounds of pollutants out of the air each year.   Many of these hang onto individual leaves or scales for several years before replacing them and often grow relatively quickly.  Even deciduous trees might host plants like mistletoe, which is evergreen and also absorbs carbon year round.  It grows attached to a tree, but produces its own food like any other plant.

Evergreen shrubs like wax myrtles form dense thickets to provide food and shelter for wildlife, privacy, shade, and fresh air.  Camellias, Mahonia, Pieris, boxwood, holly, heavenly bamboo and Ligustrum are just a few of the other evergreen shrubs common in our area.  Growing from just a few feet to perhaps 10′-15′ high in a few years, all of these shrubs have multiple benefits in addition to their ability to efficiently capture and store greenhouse gasses.  They bloom to support pollinators and produce drupes or seeds for birds.

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Mistletoe also carries out photosynthesis through the winter months.  Although it is anchored to the tree, it produces its own food, using carbon from the air.

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Woody, structural plants may be too large for some garden spaces.   Where there is space though, gardener’s can plant below them to increase their impact.  Where there isn’t space for large shrubs, gardeners can plant in pots, window boxes, or small planting beds.   Any evergreen perennial absorbs carbon.

Consider evergreen ferns like our native Christmas fern, the Asian Holly fern, and evergreen species of Dryopteris, like ‘Autumn Brilliance.’  While most new fronds are produced in spring and early summer, their fronds continue respiration year round.   These grow in shade to partial sun and help hold the soil against erosion.  While they don’t produce food for wildlife, most are also safe from rabbit or deer grazing.

Perennials like Hellebores sport huge leaves and begin producing new leaves, in active growth, throughout the winter months.  They also provide nectar for pollinators.  Arum italicum makes an attractive groundcover and ‘shoes and socks’ plant for shrubs, while producing new leaves beginning in September or October each year and remaining in active growth through at least May, as does Pachysandra.  Hardy Cyclamen actively grow from autumn through early spring, depending on their species.  Even subtle plants like Liriope, Carex, or mondo grass efficiently remove carbon from the air each day.

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Holly fern, Dianthus and Centaurea cineraria, or dusty miller, growth through the winter months in our climate.

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Succulents perennials and shrubs are important in areas warm enough to support them through the winter.  Whether large or small, each plays an important part in absorbing and storing carbon.  Some Sedums remain in growth for us here in Zone 7b, along with Yuccas, some Euphorbias, and a few other succulent plants.

Groundcover vines like Vinca, Ivy, and Smilax also retain their leaves and continue to grow through the winter. Even mosses and grasses can absorb carbon. So long as they remain green they can carry on respiration and photosynthesis.

We already have some emerging foliage from early bulbs here in Williamsburg.  In fact, I found a few clumps of daffodils already in bloom last week.  As their leaves develop, they are actively incorporating carbon into the growing plant, fueling growth above and below ground.  Geophytes store carbon as their bulbs, rhizomes, tubers and corms grow and multiply each year.  While we may plant them for their early flowers, let’s also appreciate them for the work they do purifying our air.

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Camellia japonica

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Perhaps this is why I will tolerate plant growth that others might label as ‘weeds.’  I see an active ‘carbon sink’ in every living, breathing plant.  I can see some value in the plant’s activity, even if it may not be the plant I would prefer to see growing in a particular spot.  Because once a plant is cut or pulled from the earth, and it is no longer carrying on photosynthesis, it begins to decay.  Carbon is released back into the air as the plant’s cells and molecules decompose.  While this is an inevitable natural process, let us consider the overall balance within the spaces we tend.

Let’s maximize the benefits derived from the plants we choose to grow, and look at the ecosystem we create functionally, as well as aesthetically.

Woodland Gnome 2021

Many thanks to the wonderful ‘Six on Saturday’ meme sponsored by The Propagator.

 

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