Fertilizer 101 – The Basics of Feeding Your Plants


feeding plants

Plants are living creatures, and living creatures need proper nourishment to survive. Feeding plants, however, isn’t just about dumping fertilizers on your garden beds.

If your plants are well-fed, you’ll know. You’ll see verdant leaves, sturdy stems, colorful blooms and healthy fruits. At the same time, plants become more disease resistant.

If your plants are famished, you’ll know it, too. Usually, you’ll see yellowed, mottled, shriveled or rotting leaves; plants are stunted; fruits don’t mature (or they don’t fruit at all); and flowers are ugly, disfigured or drop before setting fruit.

What to Feed Plants

But what do we feed plants? Compost, after all, isn’t a fertile source for nutrients unless it’s vermicompost.

The principal nutrients that plants need are nitrogen (N), phosphorous (P) and potassium (K), conveniently abbreviated to NPK.

If you’ve been visiting your garden center and you’ve been seeing sacks of fertilizers stamped with three numbers like 5-10-8, 5-5-5 or something similar, that’s the shorthand for the percentage content of these major nutrients in the fertilizer. So a 5-10-8 formulation on a sack of fertilizer means it contains 5% nitrogen, 10% phosphorous and 8% potassium.

Nitrogen is important because it helps form new leaves, branches and stems. Plants starving for nitrogen are slow growing; have tiny, off-colored leaves; and their stems snap easily.

Phosphorous, on the other hand, is responsible for a robust, far-reaching root system, which in turn ensures that the plant could forage for food farther afield and is more able to tolerate dry conditions. Phosphorous also supports flower development. Without phosphorous, plant roots are fair game to pests, their flowers are poorly, and the leaves and stems develops a ghastly shade of blue, purple or red (if those aren’t their natural color).

Potassium, or potash, is necessary for the general good health of the plant—size, color, and flowering and fruiting. Potassium is also vital in hardening plants against abrupt changes in environmental conditions. If it gets too hot or too cold suddenly, potassium helps shore up the plant’s defenses against these stressors. You have a potassium deficiency in your garden beds if plants leaves turn brown at the rims or curl in at the edge and the stems are mottled or weakened.

My bush beans had blotchy, yellowed leaves and the fruits remained their tiny, miniscule selves (about an inch long) months after they emerged. Turned out they were lacking in potassium. :(

There are also trace elements, called micronutrients, which plants need to be healthy and hardy. These micronutrients include sulfur, calcium, magnesium, iron, manganese, zinc, iron, copper, boron, chlorine and molybdenum. Your plants need these elements only in small amounts and the best sources are such organic fertilizers as seaweed extract, bone meal, manure, greensand, rock phosphate and granite dust.

These major nutrients and trace elements can be sourced from both synthetic and organic fertilizers.

Synthetic fertilizers are easily available and are typically less expensive. However, they do leave traces of possibly harmful substances in the soil and in water tables that could affect our health negatively.

Organic fertilizers, on the other hand, are more soil friendly though they often come at premium cost. They’re made from a blend of plant and animal ingredients, granite dust, minerals, rock phosphate and greensand and come in dry powder, granulated or pellet form.

Both synthetic and organic fertilizers could be slow release—nutrients are made available to plants gradually—and water soluble (or liquid form)—usually injected directly to the roots or as a foliar spray, when rapid feeding is required (particularly for distressed plants).

When to Feed Plants

For sure, you don’t want to feed your plants only when they’re showing signs of disease or distress.

You want to feed them before they get that way so that you’ll have a chance to reap the fruits of your labor, especially in your vegetable gardens.

The best time to feed plants is when they’re at their most active in terms of growing. Typically, this is when you’re preparing beds, transplanting seedlings, and when the plants are setting out blooms and fruiting.

Be aware that plants have different nourishment needs.

Plants like roses, corn, spinach, broccoli and cabbage, especially those whose leaves are eaten, are heavy feeders. Legumes like beans and lentils, and medium-leafed vegetables like okra need moderate amounts of fertilizer. Herbs feed sparingly.

How to Feed Plants

Feeding plants, on the other hand, is as simple as it gets. You can either broadcast or mix in.

If you’re planting on new beds, mix the fertilizer in with the soil and make sure you incorporating it thoroughly.

If you’re transplanting seedlings or fertilizing when plants are flowering or fruiting, you can broadcast the fertilizer around the immediate zone of the plants or as a side-dressing.

It’s important that you follow the recommended application rates from the manufacturer. Your plants won’t thank you for it as excess fertilizer doesn’t do much to boost their growth and could actually burn or injure your plants.

Any questions or lessons learned about feeding your plants that you want to share?

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