When our Valley air is nasty, our gardens and plants have no escape

We’ve had many summers now of smoky air, some worse than others. I hope this is not the “new norm.” Many of us are forced to stay indoors, but what’s happening in our gardens?

We know some tomato fruits were smaller than they should have been for that variety and some were larger. What else was happening?

For one thing, the appearance of some leaves changed, altering their ability to create food for their plant by photosynthesis. Apparently NASA now is looking at air quality, especially pollution by ozone at the planet’s surface level in the light of the devastating fires in our country. Ozone forms naturally in the planet’s atmosphere, and when it’s very high up in the stratosphere, it protects us from harmful ultraviolet sun rays. When it forms at the surface level, it’s harmful pollution for humans, especially those with compromised respiratory systems. It’s also harmful to some plants.

Ozone forms when there’s a reaction between nitrogen oxides and volatile organic compounds in the presence of sunlight. Volatile organic compounds involved in ozone creation are usually identified as pollutants from fossil fuel burning, as in motor vehicles, but wildfires are also contributing. Add that to the fine particulates in smoke from range and forest fires, and the air isn’t fit for humans, beasts or plants. We’re advised to stay indoors, if possible. Plants have no refuge.

Plants create their own food by photosynthesis, with open stomata (pores) on the undersides of leaves to take in carbon dioxide, essential for that plant food creation. When surface level ozone is present, those stomata take in ozone, damaging plant growth, and visible symptoms result.

Ozone-affected leaves look stippled or finely spotted on the tops of their leaves. We gardeners know that stippled leaves usually indicate damage by thrips or spider mites, but that insect spotting shows on the under sides of the leaves, not on the surface, as the ozone contamination shows. Ozone pollution has no visible effect on the veins in leaves, but very sensitive plants show small dead spots and “general leaf collapse.”

Older leaves, having been exposed to that pollution longer than those newly formed, will show greater damage than the new leaves. Since photosynthesis has been compromised, some chlorosis (yellowing) may show too, and since the plant cannot manufacture as much food as it normally should, it will produce less fruit. Not all plants are equally susceptible to damage, some more resistant or tougher than others.

In my garden, cucumbers are showing some chlorosis and spotting on the upper sides of leaves, but the fruiting vigor of Poona Kheera cucumbers hasn’t slowed down much, if at all. Sweet potato leaves, though, show no such spotting on the tops of the leaves. They’re all dark green and vigorous, except for a few of the oldest leaves, and they have large black splotches on their tops.

Pepper plants are nearly submerged in sweet potato vines, but their color is dark green, very healthy. Most other plants in my garden are looking good, although some pole bean varieties are barely hanging on to life, and tomato plants look quite ragged. Tree fruits have been more than abundant, and this year, for the first time in many years, fewer codling moths attacked pears. We found no codling moth larvae at all in white peaches for the first time in at least five years.

▪  If you know of a group of young people who want to do community service, please ask them to volunteer to glean food for the Idaho Foodbank. I’m sure we’re not the only homeowners who have fruit trees yielding more than we and friends can use, and we certainly hate for that good food to go to waste.