Xtremehorticulture

Xtremehorticulture of the Desert

Both Nitrogen and Iron Fertilizers Contribute to Dark Green Plant Color

Leave a Comment / green color, growth, iron chelates, iron fertilizer, nitrogen fertilizer /

Q. Thanks to your previous advice I used an iron chelate, applied it to the soil in March, and got my plants to develop a dark green color rather than a yellowish green color. Shrubs that the reader was speaking about. Not sure but they do look like desert natives. A. There are many things that develop a yellowish color in plants besides needing an iron fertilizer or chelate. The plant you questioned appears to be native desert plant, a Texas sage. That is odd needing an iron fertilizer for native desert plants. They are usually accustomed to our soils and don’t need iron. Watering or a nitrogen fertilizer may be the issue. Not sure but I do recommend iron chelates that contain EDDHA as the chelating agent. It works in all the different alkalinities of desert soils. EDTA and DTPA iron chelates don’t. Regardless, the two fertilizers that can create dark green leaves are nitrogen and iron. If that plant is native to the Western US, then yellowing leaves is more likely issues involving either nitrogen or watering too often. Nitrogen causes stem growth as well as dark green leaf color. Adding only an iron fertilizer or chelate causes the new growth to become green but does not stimulate new growth that much. When iron is involved, the yellowing occurs on newer growth. Yellowing due to a need for nitrogen occurs all over the plant. Also, the yellowing of leaves due to iron may be a yellow leaf color while the veins of the leaves stay a darker green. wk Winter yellowing I call bronzing of a shrub due to very cold temperatures for Las Vegas. Two types of “overwatering” can occur; watering too often or giving the plant too much water all at once. It is easier for the plant to resist “overwatering” from the second kind than the first kind. It is easy to water desert native plants too often when placed on the same irrigation line as non-desert plants. Mesquite leaf yellowing and leaf drop during winter cold temperatures. Another reason for yellowing of plant leaves are cold temperatures. This type of yellowing is more of a “bronzish yellow” leaf color and happens during cold weather. Cold weather damage to mesquite leaves (yellowing or bronzing) is a common occurrence during cold weather just before the leaves may fall from the tree if it gets cold enough.

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Am I Applying Too Much Nitrogen?

Leave a Comment / nitrogen fertilizer, plant tonics /

Q. We fertilize all of our bushes early spring and mid fall with a 5-10-5 liquid plant tonic.  Hopefully this isn’t too much nitrogen. This concentrated fertilizer  has no nitrogen but very high percentages of phosphorus and potassium A. There are two ways to look at this question. Applying too much nitrogen can mean either applying it too often or applying too much in a single application. If you follow label directions, the amount of nitrogen applied should be correct. Apply nitrogen as often as 8 weeks apart if you want continuous growth.              Applying excessive amounts of nitrogen can damage plants or cause excessive growth of leaves and stems.             When judging how much fertilizer to apply and how often, observe the plant. If the plant does not have good growth or the flower size and numbers have diminished, apply fertilizers or “plant tonics” if you prefer. Applying too much nitrogen, the first number, is not normally a long-term problem. The potential long-term problem involves the over application of the second or middle number, phosphorus.  Phosphorus stays bound in many soils for much longer periods of time than nitrogen. Apply fertilizers containing high levels of phosphorus (middle number) less often than fertilizers that contain high levels of nitrogen. As a general rule of thumb, apply fertilizers containing phosphorus once a year to established plants, two weeks before flowering. The rest of the time use high nitrogen fertilizers. The exception is at planting time. Every time seed or transplants go in the ground, apply a high phosphorus fertilizer. Before planting, mix high phosphorus fertilizers in the soil to the same depth the roots will grow. Bagged compost can be hard to find. Most bagged products that contain compost are soil mixes, not straight compost. Consider using compost instead of a mineral fertilizer. I am talking about compost which is harder to find, not a soil mix that contains compost. Most composts have a good balance of nitrogen, phosphorus and potassium and can be used as a substitute for mineral fertilizers. Composts provide plants with a lot of minor elements not found in mineral fertilizers. Compost lowers soil alkalinity, stimulates good soil microorganisms and provides humus or “black gold” to the soil. It is a very powerful addition to desert soils.

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Legumes Should Be Supplemented with Nitrogen for Optimum Results

Leave a Comment / acacia, mesquite, nitrogen fertilizer, supplement fertilizer, supplement nitrogen /

 One of the bird of the desert bird of paradise, a legume. Most legumes have characteristic flowers and leaves. Q. Do nitrogen fixers like trumpet vines and locust trees provide significant nitrogen to nearby plants?  For example the Bermuda lawn surrounding the locust or the iris and daffodils in a flower bed anchored by a trumpet vine.   A. No they don’t produce enough for our high expectations in landscapes and gardens. Nitrogen fixers (such as legumes, there are others) supply enough to help make sure they can reproduce and make seed. The objectives (if I can put it in human terms) of plants and humans are different. Plants want to survive, reproduce and out-compete with other plants for their niche. In nitrogen poor soils nitrogen fixers, like legumes, take nitrogen from the air and supplement what they can’t get from the ground. In nitrogen poor soils, legumes are fantastic competitors. In nitrogen rich soils they are not. Typical legume flower leaf and pod             The expectations of humans for the plants they care for are far greater than plant objectives. We want beauty and lushness from landscape plants and we want a good production of food from our legume crops.             The nitrogen needed to meet human expectations is far greater than the nitrogen needed to meet plant objectives. So for this reason, we need to fertilize nitrogen fixing plants with nitrogen to meet our objectives. The basic rule of thumb I use is the question, “So I want my plants to meet what they consider to be adequate (reproduction and beat out the competition) or do I want them to do more than that?” Snow pea flowers and leaves are good examples of what many legumes resemble             Most people want these plants to do far more than successfully reproduce. Some people are purists and they want that “native look” or for philosophical reasons they prefer the plant produce what it can they are happy living in the “nitrogen cycle”.  Nothing wrong with that and it meets their expectations. If you want lushness or greater production, then add extra nitrogen.             The general rule of thumb you can follow is that many nitrogen fixing plants receive only about 25%, at best, of the nitrogen they need to meet our expectations. However you can treat legumes just like any other plant and feed them extra nitrogen. Plants can be lazy. If you give them all this nitrogen, they may produce little to no nodules on the roots (the nodules contain the nitrogen fixing bacteria). Hey, its alot easier to take available nitrogen than it is to build these homes on their roots for these symbiotic bacteria that take nitrogen from the air. root nodules of legume can resemble root knot nematode infestation             We are lucky in that nitrogen fixation by legumes is far more efficient in our alkaline soils of the desert than in acid soils of high rainfall areas. So to answer your question with a short winded response, no, they will not produce enough nitrogen for surrounding plants if your landscape expectations are high. If you are a eco-purist, then maybe they will.

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