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Ozone can be stressing your garden

Hot, smoky conditions create dangerous pollutant levels

Sacramento Digs Gardening
BY Debbie Arrington PUBLISHED SEP 7, 2020

These pictures compare a normal tulip tree leaf
and one exposed to too much ozone.

(Photos courtesy National Park Service)

Smoky skies and record heat make gardening -- or just about any outdoor activity -- intolerable right now. Usually our gardens cope better with these conditions than we do; they can filter out the pollutants and conserve their resources.

But the air is so bad now, even plants are feeling ill effects.

Today (Monday) will be the 22nd consecutive Spare the Air Day for the Bay Area -- and the greater Sacramento region, a record for this current streak of poor air quality. Driving, operating gas-powered equipment, barbecuing and other activities are discouraged (if not prohibited).

The past few days that bad air has been accompanied by excessive heat, creating a ground-hugging layer of ozone. That's making our eyes water -- and our plants suffer.

Ozone is created by a combination of wildfire ash and other pollutants (usually nitrogen oxides and volatile organic compounds), intensified by bright sunlight and triple-digit heat. It can prevent a plant's leaves from properly doing their job. Ozone enters the leaves' stomata and burns the leaves' tissue.

Signs of ozone damage include dark stippling and bleaching of foliage. Plants lose their vigor and stop blooming or yielding fruit. Ozone damage weakens the plant and makes it much more susceptible to pests and disease.

Worried about the long-term effects of too much ozone, researchers and the National Park Service surveyed plants in national parks across the country and found hundreds of species with ozone sensitivity, from ash and asters to sycamores and yarrow. Maple, cherry, poplar and plum trees are all on the ozone-sensitive list. Find it here: https://irma.nps.gov/NPSpecies/Reports/Systemwide/List%20of%20Ozone-sensitive%20Species

What can you do to help your plants cope? Keep them hydrated. Offer them some afternoon shade. Wash ash and soot from leaves.

And continue to "Spare the Air." These smoky conditions are expected to last at least through Wednesday.

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Keywords:

gardening Sacramento heat ozone damage trees heat wave air quality heat stress leaves

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Dig In: Garden Checklist

For week of June 4:

Because of the comfortable weather, it’s not too late to set out tomato and pepper seedlings as well as squash and melon plants. They’ll appreciate this not-too-hot weather. Just remember to water.

* From seed, plant corn, pumpkins, radishes, melons, squash and sunflowers.

* Plant basil to go with your tomatoes.

* Transplant summer annuals such as petunias, marigolds and zinnias.

* It’s also a good time to transplant perennial flowers including astilbe, columbine, coneflowers, coreopsis, dahlias, rudbeckia, salvia and verbena.

* Let the grass grow longer. Set the mower blades high to reduce stress on your lawn during summer heat. To cut down on evaporation, water your lawn deeply during the wee hours of the morning, between 2 and 8 a.m.

* Tie up vines and stake tall plants such as gladiolus and lilies. That gives their heavy flowers some support.

* Dig and divide crowded bulbs after the tops have died down.

* Feed summer flowers with a slow-release fertilizer.

* Mulch, mulch, mulch! This “blanket” keeps moisture in the soil longer and helps your plants cope during hot weather.

* Thin grapes on the vine for bigger, better clusters later this summer.

* Cut back fruit-bearing canes on berries.

* Feed camellias, azaleas and other acid-loving plants.

* Trim off dead flowers from rose bushes to keep them blooming through the summer. Roses also benefit from deep watering and feeding now. A top dressing of aged compost will keep them happy. It feeds as well as keeps roots moist.

* Pinch back chrysanthemums for bushier plants with many more flowers in September.

Send us a gardening question, a post suggestion or information about an upcoming event. sacdigsgardening@gmail.com