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Wildfire brings more ozone problems

Sacramento Digs Gardening
BY Debbie Arrington PUBLISHED AUG 30, 2021

These citrus leaves show ozone damage. (Photo

courtesy UC IPM)

Hot, smoky conditions
create high pollutant levels

Plants may be able to cope with wildfire smoke better than people. But ozone is another matter.

After prolonged exposure to two weeks of wildfire smoke, foliage on many plants in the greater Sacramento area are showing signs of ozone damage. It starts out as stippling – little dots all over large leaves. Or parts of leaves may look like they were sun-bleached white or silver.

In my Sacramento garden, I noticed it in particular on a large dahlia plant. Besides funky foliage, its vivid red petals also were bleached white at the tips. That bleaching was accompanied by a build-up of soot on its leaves.

Ozone is what happens when wildfire ash and other pollutants get “cooked” by triple-digit heat. It makes our eyes water and throats hurt. And there’s a lot of it right now.

According to Sacramento region air quality monitors, our air quality is rated “very unhealthy” for the next several days with particle levels remaining high, especially in El Dorado and Placer counties. Through at least Thursday, Sacramento is forecast to rate 250 on the Air Quality Index. (“Good” is below 50.)

While ozone high up in the atmosphere is a good thing, ground-level ozone can be dangerous. In our case, it’s 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.

Ground-level ozone can prevent a plant's leaves from properly doing their job. Ozone enters the leaf's stomata and burns the leaf's 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, polar and plum trees are all on the ozone-sensitive list. Find it here: https://irma.nps.gov/NPSpecies/Reports/Systemwide/Ozone-sensitive%20Species%20by%20Park

Meanwhile, keep plants hydrated. Wash ash and soot from leaves. Lower temperatures later this week may bring some ozone relief, too.

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Keywords:

ash Sacramento plant vigor smoke wildfires weather gardening gardening in smoke air pollution heat air quality ozone UC IPM

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Garden Checklist for week of Nov. 3

November still offers good weather for fall planting:

* If you haven't already, it's time to clean up the remains of summer. Pull faded annuals and vegetables. Prune dead or broken branches from trees.

* Now is the best time to plant most trees and shrubs. This gives them plenty of time for root development before spring growth. They also benefit from fall and winter rains.

* Set out cool-weather annuals such as pansies and snapdragons.

* Lettuce, cabbage and broccoli also can be planted now.

* Plant garlic and onions.

* Keep planting bulbs to spread out your spring bloom. Some possible suggestions: daffodils, crocuses, hyacinths, tulips, anemones and scillas.

* This is also a good time to seed wildflowers and plant such spring bloomers as sweet pea, sweet alyssum and bachelor buttons.

* Rake and compost leaves, but dispose of any diseased plant material. For example, if peach and nectarine trees showed signs of leaf curl this year, clean up under trees and dispose of those leaves instead of composting.

* Save dry stalks and seedpods from poppies and coneflowers for fall bouquets and holiday decorating.

* For holiday blooms indoors, plant paperwhite narcissus bulbs now. Fill a shallow bowl or dish with 2 inches of rocks or pebbles. Place bulbs in the dish with the root end nestled in the rocks. Add water until it just touches the bottom of the bulbs. Place the dish in a sunny window. Add water as needed.

* Give your azaleas, gardenias and camellias a boost with chelated iron.

* For larger blooms, pinch off some camellia buds.

* Prune non-flowering trees and shrubs while dormant.

* To help prevent leaf curl, apply a copper fungicide spray to peach and nectarine trees after they lose their leaves this month. Leaf curl, which shows up in the spring, is caused by a fungus that winters as spores on the limbs and around the tree in fallen leaves. Sprays are most effective now.

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