Orange County Farm Supply
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The Role of Fertilizers on Plumerias*

We can safely say that all we plumerias enthusiasts are out to get those beautiful blooms! Besides ample sunlight, Plumerias require consistent fertilizing.

Fertilizers usually contain the primary nutrients: nitrogen, phosphorus, potassium. They should also contain secondary nutrients, which are calcium, magnesium, and sulfur. To complete the mix, fertilizers should contain the micronutrients iron, zinc, manganese, copper, molybdenum, boron, and cobalt.

Plumerias usually like low nitrogen, high phosphorus, and high potassium with all the secondaries and micronutrients. Nitrogen promotes growth and foliage development. Phosphorous promotes blooms, reproductive activity, and root development. Potassium helps with overall vigor, branch thickness, and resistance to insects and pathogens.

Chemicals VS Organics

Fertilizers that are chemically based should be thought of as feeding the plants and not feeding the soil. Repeated applications of chemical fertilizers can slowly deplete microbial activity in soils. However, the plus side is that chemical fertilizers are vey cost effective and results are quick and intense.

Organic based fertilizers should be thought of as feeding the soil. The plants get the nutrients from the soli and this process is more timely. Results are also intense but the negative aspect is that organic fertilizers are not as cost effective.

Typically, chemical fertilizers can be obtained in many forms, i.e., pellets, and water-soluble. There are also supplements like Epsom salts (magnesium sulfate), Sul-po-mag (sulfur, potassium, magnesium) and potassium sulfate (0-0-50). The magnesium in Epson salts is essential in the formation of chlorophyll. It should be used monthly as it benefits the roots and flowers. Epsom salts also helps prevent sunburned leaves on hot summer days. Sul-po-mag and potassium sulfate should be used in May to help strengthen stems for the stress of flowering and again in October for hardening the stems for winter. (Winterizing).

Organic fertilizers come in liquid as well as solid/granular forms. Fish emulsion and liquefied kelp are excellent liquid forms. Liquid kelp is great for foliar feeding but be careful to wash it off the flowers as it may temporarily stain them. Dr. Earth has an excellent granular fertilizer: Bud and Bloom Booster for Tropicals (4-10-7). It contains fish bone meal, feather meal, potassium sulfate, alfalfa meal, and kelp meal. In addition, it contains 7 different beneficial microbes to help accelerate breakdown and availability of nutrients, therefore it is biologically active, Good supplements are green sand for a potassium source (0-0-3) and fish bone meal (3-18-0), as opposed top bone meal (bovine) (2.5-12-0) for phosphorus source.

The last thing I think we should touch on is Mycorrhizae. Mycorrhizae are a beneficial fungus that has a symbiotic relationship with the plants’ roots. Think of it as a bridge between the plants roots and the nutrients in the soil. This beneficial fungus attaches itself to the tips of plant roots and extends deep into soils (much further than plant roots) and brings nutrients to the host plants. Think of this as an inoculants. The plant benefits as does the Mycorrhizae because the fungus receives the life force from the plants. It should be noted that use of fungicides will kill off Mycorrhizae and the over use of high phosphate fertilizers may decline the efficiency of this fungus. Phosphorous is key to flowering , so one way to overcome that is to foliar feed and not drench the soil with water soluble chemical fertilizers such as Grow-More 6-30-30.

For Plumerias, the best form of mycorrhizae is a water-soluble kelp based powder that contains 12 different types of fungi. All that is required is a teaspoon per gallon of water and drench the root zone. One inoculation can last for years.

In closing, you can feed your Plumerias monthly, during the growing and flowering season, do not fertilize or water Plumeria during their dormant season.

* Reprinted from Orange County Farm Supply Newsletter, Fall 2001, Volume 1, Issue 1