Recommended Readings:

The Garden Doctor books I, II, III – By Jacob Mittleider
Rodale’s All New Encyclopedia of Organic Gardening

Just like people, if plants don’t get all the nutrients they need, they will not develop like they should. It is so frustrating to plant seeds, watch them emerge as tiny seedlings, then develop deformed leaves, turn brown or yellow, then curl up and die.

Unfortunately, that is how it goes for many a first time, second time, third time gardener who is faithfully and hopefully trying to grow a garden. It can be so discouraging that you just want to throw in the towel and quit. It is of great value to learn to read the leaves of your plants in order to know what plant deficiencies exist. The leaves will tell you if the plant is happy and healthy or lacking in important nutrients.

The three most important and most recognized nutrients are Nitrogen, Phosphorus, and Potassium. If one of these is lacking, you will have a problem. It will show in the leaves. There are some others that are also very important, but seldom talked about. They are Calcium, magnesium, sulfur, and iron. Naturally occurring supplies of these nutrients are usually sufficient in most garden soils, but not always, especially if the plot has been gardened for a long time, or if the plant needs more of a certain substance than other plants do. The best way to insure there are correct amounts of nutrients is to run a soils test yourself (See our lesson on soil testing,) or send your soil sample into a lab for testing. Most people aren’t interested in being so scientific, yet if you are a gardener for long, you will become a scientist as well. Gardening, ph balance, nutrients, minerals, water, light, its all about science and experimentation. We want to shorten your learning curve though, so here are some things to watch for.

Yellowing leaves

The tricky thing is, leaves will turn yellow if they are deficient in iron, nitrogen, potassium, and magnesium. So how is one to know what to supplement with?

Even though yellowing is a common symptom, there are other signs – especially early on – that will give the observant gardener a hint as to what the problem is. So pay close attention to the leaves and then act quickly with the right soil amendment allowing the plant to overcome the deficiency before it affects yield or kills the plant all together. It may take as long as two weeks to see improvement and you will need to look for it in the new growth. Often the older leaves can not recover.
Here are some common problems that are easily remedied:


Nitrogen Deficiency A UNIFORM yellowing of the plant leaf that begins from the inside of the leaf and moves to the edges, leaves rolling upward (tomato plants.) Pale green leaves with oldest leaves turning yellow first. Ammend with compost, manure, or feed the microbes in the soil which will feed the plants (Nano Ag Answer products)


phosphorus deficiencyLook for purple color on leaf edges. Corn will be purple striped. Underside of potato leaves are purple and the leaf tips are curled. Veins will turn purple in tomatoes and leaves will curl. When you see purple think phosphorus. Note: sometimes it can be magnesium, but there will be other symptoms present with magnesium that are not present in phosphorus deficiency. Amend with bonemeal or rock phosphate.


Potassium DefIn potassium deficiency the leaves turn yellow too, however, they turn yellow from the outside in. It is not a uniform yellowing of the leaf. Often the inside is still green. The edges of the leaves will begin to go yellow and then they will turn brown and die. The leaf edges will begin to look ragged or burned. Two more early signs to look for are white dots or specks on the leaves and leaves that are not fully developed, are missing parts or look torn and stunted. These last two signs will help differentiate between other deficiencies that cause yellowing. Amend with greensand, granite, or lightly sprinkle with wood ash from clean wood (unpainted.)


iron-chlorosis-on-maple-treeIron deficiency can look just like nitrogen deficiency. It is always good to know what plant you are dealing with because some plants are just more susceptible to iron deficiency. Strawberries are a good example. In iron deficiency the leaves turn yellow, but the veins stay green. As the problem of iron chlorosis worsens, the leaves will fire and die. Poor overall growth is another symptom. Amend with chelated iron. If you use another iron product, it may not be in a form available to the plant and may have to break down in the soil for about a year before the plant can take it up. Also, it is very important to check your drainage. Poor drainage may be the problem. Correcting drainage can sometimes clear up an iron chlorosis problem.


Calcium DeficiencyI believe calcium is highly underrated. Calcium makes all other nutrients more available to the plant and is extremely important. To read more about calcium click here. It is a macronutrient and the building block of cell walls. Calcium deficiencies are usually seen in acidic soils and that is why farmers in those areas will lime their fields on a yearly basis. Typically calcium deficiencies will cause leaves to look warty or all puckered up. Often the leaf edges will look tight or sort of curl in. Sometimes the deficiency can be seen on the underside with brown sunken dots. Most often the leaves remain green but plants are dwarfed and stunted looking. In tomatoes the oldest leaves will turn brownish yellow on the inside and die. Amend with gypsum on alkaline soils and lime on acidic soils. Eggshells and oyster shells can also be used.


In sulfur deficiency the leaves turn a creamy color. Its like they are all washed out. It isn’t really a yellowing, but just a lack of color or sort of a bleached out creamy-white. The biggest difference between sulfur deficiency and nitrogen deficiency is the severity of the discoloration in sulfur deficient plants and the fact that the leaves are not uniformly discolored nor do they die back in the early stages of deficiency. Also, the young leaves are turning yellow, not just the older leaves. Sulfur deficiency is on the increase. As a vital nutrient to plants, yearly additions of sulfur should be about 100 lbs. per acre. I always say sulfur makes everything green. Amend with magnesium sulfate, potassium sulfate, calcium sulfate, ammonium sulfate, or ferric sulfate. Or you can just use sulfur. I feed my plants magnesium sulfate on a regular basis – especially my flowers in pots.

For a more complete list of substances you can use to amend the soil in your garden, refer to our resource section.


There are actually 13 essential nutrients which include: nitrogen, potassium, phosphorus, calcium, sulfur, iron, magnesium, manganese, copper, iron, zinc, boron, and molybdenum. If you are using crop rotation, applying compost to your beds, adding back the elements by applying products such as AZOMITE and feeding the microbes in the soil, you shouldn’t have much of a problem with deficiencies. However, as hard as we try, they will sometimes appear.

At Roberts Ranch and Gardens we practice “no till” gardening encouraging the earthworms to do that work for us. We rotate crops, add AZOMITE to the soil with every planting and a healthy layer of compost. We also supplement the micro-organisms with a couple of applications of Nano-Ag Answer every year, feeding the microbe community that in turn will feed the plants. AZOMITE is a mined product containing more than 65 elements and includes all of the elements I discussed above. I don’t ever have to worry about putting on too much because it is in natural form and the plant seems to take up what it needs.

If you’d like to try some Azomite we’d be happy to ship it to you! Click Here To Order!