Herself’s Houston Garden

In addition to Secondary plant nutrients, and primary plant nutrients. Micronutrients are essential for plant growth but only in extremely small amounts. Usually just adding a little organic matter ( worm castings, compost etc ) will take care of all your plants micro nutrients. This is more of an issue in food crops for humans and animals. Lack of micronutrients in food crops can cause diseases related to these deficiencies in humans and animals. So be especially sure your herb and vegetable garden get a bit of organic matter each year.

Signs of micronutrient deficiencies in plants:

Boron deficiency - newest buds die, stems may crack and split, young leaves are distorted in shape, plant may not set seeds.

Chloride deficiency - roots are highly branched with stubby tips, leaves wilt then become mottled and tip wilts.

Copper deficiency - leaves are very dark green, stunted growth plants wilt even when given sufficient water.

Iron deficiency - yellow leaves with green veins, yellowing begins at center of leaf where it attaches to the stem

Molybdenum deficiency - older leaves yellow, newer leaves are light green

Zinc deficiency - yellow and brown mottling of leaves, green veins, also small leaves that are distorted.

An excess of one micronutrient usually causes a deficiency of another micronutrient.

See also:
Secondary plant nutrients
Primary plant nutrients

More information:
Progressive gardens has photos of several deficiencies in plants

In the Houston area soil is poor for most of us.  We either have sand or clay.  Rare is the lucky soul with loam.  To make matters worse we tend toward alkaline soil, the more north and west you go the worse it gets.  Then the heat and humidity rapidly breaks down what little organic matter the soil contains.  This means we see lots of nutrient problems with plants.  Plants need much more fertilizer here than anywhere else you’ve lived.  But the biggest pollutant in our bayous is fertilizer run off.  So feed your plants lightly and frequently and watch for signs they may be missing something.

If you are seeing yellowing leaves with green veins you might want to check your plants secondary nutrients.  Iron is usually but not always the cause of green veined, yellow leaves.  Sulfur deficiency effects new leaves first, calcium and magnesium effect older leaves first.

Calcium deficiency - Youngest leaves looked bleached, especially at the tips of the leaves. Leaf tips rolls and appear scorched. Along the edges of the leaves the veins remain green while leaf looks bleached out. New leaves may be distorted in shape. Old leaves turn brown and die. Growth is stunted, new buds don’t grow. In vegetables you get blossom end rot and black spots in things like celery, carrots and cabbage. Usually this only occurs in very acidic soil.

Calcium is needed to build plant cell walls, and to help move nutrients through out the plant.

Calcium is usually not a problem if your soil pH is between 6-8. Too much or too little water can also effect calcium levels in the plant.

Magnesium deficiency - Older leaves become yellow, while veins remain green.  Leaves drop off plant. Leaves may curl up at edges and edges become red-brown-purple in color leaving a green arrowhead shape in the center of the leaf.

Magnesium is needed for photosynthesis it is the main element in the chlorophyll molecule. It helps the plant uptake iron and also to move nutrients around the plant.

Add epsom salts 1 teaspoon per gallon twice a year to fix a magnesium deficiency.

Sulfur deficiency - Youngest leaves yellow, veins remain green. Plant is slow growing. Often sulfur is not deficient but rather just low compared to the amount of nitrogen in the soil. Sulfur deficiencies are rare. Adding sulfur will help lower your soil pH, slowly and lightly, so don’t be afraid to add some to your soil if your pH is higher than 7.0.

Too much of these nutrients are not usually a problem except that other nutrients can’t keep up. So too much of any of these may cause a deficiency in another nutrient.

See also:
Primary plant nutrients
Soil testing

More information:
114 Photos of mineral deficiencies in plants

I know you’ve all heard of pH and those of you with pools are probably very familiar with pH. But why do you care about your garden soil pH?

The ‘p’ in pH stands for ‘potenz’ ( potential to be ) and the ‘H’ is for ‘Hydrogen’. So pH is just a measure of the amount of hydrogen in your soil. The scale runs from 0 to 14 ( acidic to alkaline ) and you are aiming for 6-7 but your plants will be thrilled with anything between 6-8.

I have no idea what my soil pH is, I’m waiting for my soil test to come back. However I’m told the Houston area has acidic soil, most everything north and west of us has alkaline soil.

The pH is important to plants because plant nutrients are not soluble when the pH is too high or too low. 98% of the nutrients your plant needs it gets when the roots take in water. If the pH is too high or too low the nutrients in the soil do not dissolve and your plants can’t use them.

Think about being stuck on a plane. You have a bag of cookies in a sealed plastic bag and nothing sharp to slice the bag open. You have the food but no way to eat it. This is what happens to your plants when your soil’s pH is too far from center.

If your soil tests below 6.0 you’ll want to add limestone to your garden. The amount you add depends on how acidic your soil is. Limestone takes a very long time to work its way down into the soil so it may take a while to see your results.

If your soil is about 8.0 you’ll need to add sulfur to it to lower the pH. This also is a very slow process. If you add to much sulfur too quickly you’ll wipe out your plants.

pH should be checked yearly. ( Yes, I know, I’ve been gardening forever and this is my first year testing but better later then never. It just shows you can teach an old gardener new tricks. ) You can send a sample to the county for testing. Many garden supply places carry soil pH kits.

Nitrogen, Phosphorus and Potassium are the three primary nutrients in any fertilizer. The three numbers on your fertilizer container represent Nitrogen (N), Phosphorus (P) and Potassium (K) in that order. The number is the % by weight of the nutrient contained.

Nitrogen is the primary building block for plant protoplasm. Protoplasm is the translucent substance that is the living matter in cells. It is needed for flower differentiation, speedy shoot growth, the health of flower buds and the quality of fruit set. It also acts as a catalyst for the other minerals.

If you have too little nitrogen leaves become yellow-green, the oldest showing yellowing first. You will see the tips of leaves turn brown and the brown will be surrounded by yellow than green. The brown and yellow strips are V-Shaped. Since the plant can move nitrogen, when it is low it takes it from older growth and gives it to newer growth. Growth is reduced, there will be less and small fruits.

If the nitrogen is too high then fruits take longer to ripen, will be soft and have short storage life. Too much nitrogen also hurts root growth and water efficiency of plants. It also will make your plants less tolerant of our cold spells.

When buying nitrogen for your plants spend the money for the slow release formula. Soluble can cause leaf burn and rapid growth for a week then nothing. Soluble must be reapplied frequently and in the end costs more because you need to apply it more often. Except of course in your vegetable bed where you want rapid growth for the short growth season.

Phosphorus is needed for energy transfer and storage in plants. It is needed for the formation of nucleic acids ( RNA and DNA ). It helps plants to mature and promotes root, flower and seed development.

Phosphorus is also mobile in the plant showing in older leaves first. Too little phosphorus causes leaf die back, older leaves stems and veins may appear purple. The plant will be slow reaching maturity with poor seed and fruit quality.

Potassium is needed to activate enzymes, form sugars and oils. It improves cold weather tolerance. Fruits will be a better quality with better color, less acidity and more oil and thicker skins.

Potassium is also mobile, too little potassium causes leaves to curl and distort, oldest leaves first. Older leaves may get brown edges and tips and drop. Stalks may be weak or short. Root systems will not develop properly.

If potassium is too high then there might not be enough nitrogen to keep up and a nitrogen deficiency can develop.

It is important to keep nitrogen and potassium in balance. Higher nitrogen and less potassium is good for leaf growth, your lawn and other foliage plants prefer this. High potassium lower nitrogen is better for flower, fruit and vegetable growth.

More information:
Progressive gardens has photos of several deficiencies in plants