Smoke and high heat? Watch out for ash, ozone damage

Maybe consider wearing a facemask while gardening?

Ash on the leaves of plants is a reminder: With wildfire smoke comes fine particulate matter. That stuff can get in your lungs – as well as clog plant pores.

So far this wildfire season, we’ve been relatively lucky in Sacramento; our air quality has remained “moderate” to “unhealthy for sensitive people” instead of downright unhealthy for everyone.

We already have unhealthy heat; the National Weather Services issued a “heat advisory” for the Sacramento region through Wednesday night with highs of 107 to 112 degrees possible.

Triple-digit heat coupled with wildfire smoke can create another problem for plants: Ozone damage. It starts out as stippling – little dots all over large leaves. Or parts of leaves or petals may look like they were sun-bleached white or silver.

Ozone is what happens when wildfire ash and other pollutants get “cooked” by temperatures more than 100 degrees. It makes our eyes water and throats hurt. (Think of a real smoggy day.)

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

Some plants are more prone to ozone damage than others. Researchers at the National Park Service surveyed plants in national parks and found hundreds of species with ozone sensitivity, ranging from asters to elderberries, sycamores and yarrow. Various maple, cherry, poplar and plum trees are all on the ozone-sensitive list.

In the meantime, tackle the ash and heat with the same remedy – water. Keep plants hydrated. Wash ash and soot from leaves. And look forward to lower temperatures later this week; more normal temperatures will not only bring some relief from the heat but reduce the change of ozone damage.