Sorry: correction: the latter part of first line should read:
For the first time I'm noticing leaf chlorosis among a variety of plants, across the yard, that suggest a nutritional deficiency.

Thanks.

Adding chelated iron might help if the problem is a deficiency of iron in the soil...or if the iron present in the soil is not in a soluble form (a much more likely problem). But it's a bit more complex than that. Plant nutrition is affected by the interaction between many different ions in the soil. There may be iron in the soil that is unavailable to the plant at a given temperature or soil pH. Or the iron ions that were in the soil have found other elements to bond to and are now the anions of compounds. Excess phosphorus or aluminum can bind iron in the soil. Potassium-poor soils can lead to iron chlorosis in plants. Manganese deficiency can also look very much like Fe deficiency.

For fast correction, apply a foliar iron spray directly to the leaves. As a long term remedy, composting and adding manure or other humusy bulk to the soil will help to keep the iron in a chelated state that plants can use. You might try adding a bit of Ironite to a single affected plant and see if there's a dramatic difference. If so, the iron present in your soil is probably not in a sufficiently soluble form. Also try increasing potassium and see if that fixes the problem.

If you add iron be sure to research the different brands, some have led and arsenic. If I was eating from the bed I was adding iron to, I would only add human grade iron. What I mean is I would buy iron pills the kind humans take as in vitamins. But, maybe it is not iron per sec, it could be a lack of organic matter has lead to poor soil health and a lack of micro organisms. You can fix this with bagged soil amendments or start a compost pile. Go to the soil forum here to get more helpful tips.

Thanks for the useful information. Did some more research and most sites state that iron is seldom lacking; it's the plants' ability to absorb it due to other deficiencies. Also thanks for the tip on the food grade iron.

Heading to soil forum and will continue researching!

Some plants such as Gardenia tend to be exhibit signs of Chlorosis, but with an assortment of plants I would only add a finished compost, which will buffer any abnormality and over time correct apparent signs of chlorosis. Bay area soils, according to my lab man, will usually have an abundance of both potassium and phosphorus, though usually short of nitrogen which is easily leached away with our winter rains. Al

By the way some types of the liquid miracle grow plant food have iron and there is a osmocote type that has iron "osmocote plus", but not sure if these are safe. I just know ironrite is the bad one. But, I have used both of the above and get good results. A small dose of miracle grow in a watering can will correct leaves that are looking a bit yellowish.

And to add some additional info to Al's excellent suggestion, the addition of compost will help to keep the soil a bit more acidic which unbinds the micronutrients and makes the available for uptake. For most of us (not all, but most) in California, don't have a lack of iron or other micronutrients but our soil may be alkaline enough that in combination with our unseasonably cool and wet weather cause issues with uptake of micronutrients. Pile on the compost, water in, and if you then feel compelled to provide micronutrients to your ornamentals and citrus, apply a water soluble micronutrient product. Grow More Citrus Grower's Blend is a great choice for citrus, and can be applied either to the ground and watered in, or as a foliar spray. Check with your local garden center for other micronutrient options.

Patty S.

Patty S.