There is nothing more satisfying than getting a plant species to flower. Then, after understanding a plant's life cycle, more attention can be focused on the ecology of a garden. Figuring out how your plants interact with their surrounding environment is imperative and makes it a lot easier to tweak conditions to improve plant growth and garden productivity.

The selection of nutrients, additives and supplements available in the gardening industry is extensive and it is important to understand the interaction between the grow media and roots when deciding what to feed, and how to care for, plants.

After becoming familiar with a plant's life cycle, subtle changes in leaf color, shape and texture become regular observations. Noticing this, I experimented with different nutrients, supplements and additives to counteract the deficiencies and gaps in my indoor ecosystem. After researching tons of fertilizers, I noticed a common ingredient amongst all of them, EDTA, and I decided I needed to figure out how it was affecting my plants.

Some fertilizers contain chelates (i.e., ironEDTA) that act as a packaging system to deliver essential micronutrients to a plant. A chelate is a chemical compound made up of a metal ion and a special molecule called a chelating agent. The molecular structure of a chelating agent, or ligand, is interesting because it forms multiple bonds with one metal ion, making it super stable.

Macronutrients like nitrogen, phosphorus, potassium, calcium, magnesium and sulfur are absorbed relatively easily by plants. The metal ions required for plant growth, called micronutrients (iron, zinc, copper, manganese, chlorine, boron, nickel and molybdenum are a few examples), can bond with another ion or molecule in the grow media or solution, thus rendering it unavailable for plant uptake.

Under high pH growing conditions, iron, manganese, zinc and copper react with ions to form insoluble substances that cannot be absorbed by the roots. However, if a micronutrient reacts with a chelating agent, it becomes stable in the media until the root requires it.

After the chelating agent delivers the micronutrient to the root, it returns to the grow media, bonds to another essential micronutrient and continues the cycle. The chelating agent does not lock out nutrients when it returns to the media; rather, it finds another metal ion to bond with to become stable. Chelating agents have a high affinity for metal ions-the micronutrients plants want-so they reduce the formation of unwanted precipitates that the roots cannot absorb.

Many fertilizers include synthetic chelates to increase the uptake of nutrients by plants. The most commonly used synthetic chelating agents are:

  • EDTA (ethylenediaminetetraacetic acid)
  • DTPA (diethylenetriaminepentaacetate)
  • EDDHA (ethylenediaminedihydroxy-phenylacetic acid)

EDTA is the cheapest synthetic chelating agent to produce; however, it's not totally effective in the pH range commonly used for gardening. And, while EDDHA has been tested to show the most significant increase in productivity and growth, it is the more expensive synthetic chelating agent.

Natural chelating agents are siderophores, organic acids and amino acids. Micro-organisms and plant roots release different siderophores to roam the media looking for iron that is complexed, or in an insoluble form that cannot be used by a plant, to chelate with (i.e., to bond with a metal ion to become stable) to make it available for uptake by the roots.

Beneficial micro-organisms create chelates in the process of digesting organic materials in the grow media. Plant roots can also release exudates that have natural chelates (e.g., mugineic acid, which is released by grassy plants in low iron environments).

Compost tea made from quality ingredients (visit your local hydroponic shop for more information) is an excellent way to introduce beneficial micro-organisms to the grow media and the plant canopy. Micro-organisms will colonize the root zone and leaf surface in a healthy garden via compost tea watering and foliar application. These beneficial micro-organism colonies will chelate any micronutrients and make them available to the roots and stomata.

The ecology of your garden relies heavily on the health of your plants and their surrounding environment. In a healthy ecosystem, all of the components are working together and there are no pest problems (a definite indicator of weak, unhealthy plants) or disease. Natural and synthetic chelates each have their own range of benefits. Therefore, it is important to understand the function of a chelate and how they can maximize the growth and productivity of your garden.

Understanding how your plants grow, from seed all the way to harvest, is essential. Take your observations to the next level and tune into the plant-environment interactions to make your next grow the most efficient and the most productive ecosystem yet.