How Plants Feed Themselves

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How Plants Feed Themselves

To say that we fertilize our plants to feed them is technically incorrect.

This is because plants really do feed themselves through a process called photosynthesis. Simply put, photosynthesis is the conversion of light or solar energy into chemical energy.

Certain plant cells contain a substance called chlorophyll. When chlorophyll (which also gives plants their green color) is exposed to light, plants are able to convert a combination of carbon dioxide and water into simple sugars, water and oxygen. This means plants are removing carbon dioxide from the environment while also producing the oxygen we need to breathe and the basic sugar compounds that become the foods we need to eat. Through additional internal processes, plants are able further to process these simple sugars into more complex sugars, starches and even proteins, all of which are used in any number of areas in plant growth, survival and reproduction.

How successfully a plant photosynthesizes can be the result of a number of outside factors. How much sunlight (or artificial) light is available can have an impact. Light is measured both in its intensity, duration, and type of light on the spectrum. How much carbon dioxide is available can make a difference, too. The temperature can also have an impact; photosynthesis increases rapidly in warmer environments, but at rates above around 80F, it begins to top out. At very warm temperatures, plants can begin to lose water faster than they can replace it, and water is a last critical input plants require to create their own food. In a situation in which any of these items are out of balance, the food creation factory – aka photosynthesis – risks a shutdown.


Choosing the right plant for the right location will help ensure your plants are able to photosynthesize properly and look their best. For instance, uniquely colored Black Mondo grass offers rarely seen true black coloration when grown in sunny locations, but when planted in a shady spot, this grass-like lily will begin to look more green than black. This is the result of the plant creating more green-colored chlorophyll by which to produce more food under limited light locations. Summer blooming hydrangeas often end up wilting just as their blooms are getting showy. Even if we dig into the soil and find plenty of moisture, hydrangeas may continue to crash during the heat of the day. This daytime wilting is often the result of the plant shutting down its photosynthesis factory for a few hours because the temperature is so warm that the plant cannot successfully take up water faster than it is releasing it through the under sides of its leaves. By closing the pores that release water, the plant also stops the uptake of water, slowing photosynthesis. Later, when night temperatures cool, the plant will begin taking up water, refilling the leaves, ending the wilt and preparing the photosynthesis factory to resume operations when the sun rises the next morning, none the worse for their mid-day wilt.

Plants do require a number of nutrients they do not produce themselves. This is why we provide fertilizers. Fertilizers may come in the form of composted mulch applied to the soil and later broken down into nutrients plants can use by creatures like worms that live in the soil eating organic materials. Or, it may come from a natural organic or synthetic fertilizer product purchased at a nursery.


The three numbers shown on every processed fertilizer product always refer to Nitrogen (N), Phosphorus (P) & Potassium (K) – in that order. Although plants need a number of other nutrients, these are considered “the big three”. Among other things, Nitrogen is a critical to a plant’s ability to create chlorophyll, without which photosynthesis is not possible. Phosphorus assists in root, flower and fruit growth as well as other things. Potassium helps plants with overall vigor. However, none of these fertilizer ingredients actually feed the plant; they help the plant feed itself.

Remember every soil is different and every plant nutrient requirement is different. Testing soil before randomly applying any old fertilizer off the shelf will help save you money by targeting exactly which and how much of each input nutrient you may or may not really need to help your plant feed itself as it seemly magically converts carbon dioxide, water and sunlight into the building blocks that feed and oxygenate the world.