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Wildfire brings more ozone problems



Blotchy green citrus leaves
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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Dig In: Garden Checklist

For week of March 24:

In between cloud bursts, try to catch up with early spring chores. 

* Attack weeds now! Get them before they flower and go to seed. Take a hoe and whack them as soon as they sprout. Aim for 1 inch below the soil line.

* Start preparing vegetable beds. Spade in compost and other amendments.

* Prune and fertilize spring-flowering shrubs after bloom.

* Feed camellias at the end of their bloom cycle. Pick up browned and fallen flowers to help corral blossom blight.

* Feed citrus trees, which are now in bloom and setting fruit. To prevent sunburn and borer problems on young trees, paint the exposed portion of the trunk with diluted white latex (water-based) interior paint. Dilute the paint with an equal amount of cold water before application.

* Feed roses with a balanced fertilizer (such as 10-10-10, the ratio of nitrogen, phosphorus and potassium available in that product).

* Prune and fertilize spring-flowering shrubs and trees after they bloom. Try using well-composted manure, spread 1-inch thick under the tree. This serves as both fertilizer and mulch, retaining moisture while cutting down on weeds.

* Cut back and fertilize perennial herbs to encourage new growth.

* Seed and renovate the lawn (if you still have one). Feed cool-season grasses such as bent, blue, rye and fescue with a slow-release fertilizer. Check the irrigation system and perform maintenance. Make sure sprinkler heads are turned toward the lawn, not the sidewalk.

* In the vegetable garden, transplant lettuce and cole family plants, such as cabbage, broccoli, collards and kale.

* Seed chard and beets directly into the ground.

* Plant summer bulbs, including gladiolus, tuberous begonias and callas. Also plant dahlia tubers.

* Shop for perennials. Many varieties are available in local nurseries and at plant events. They can be transplanted now while the weather remains relatively cool.

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