Fertilizing with the right fertilizer at the right time is important for maintaining healthy plants.

The Basics of Fertilizer

Determining the best fertilizer to use for various purposes can be a challenging task. What do all those numbers mean?

When selecting a fertilizer, the first question to answer is, "What analysis do I need?" The analysis is the three numbers you see on every fertilizer label, such as 12-8-8, 10-10-10 or 16-4-0. These numbers represent the percentage of the three major nutrients required for optimal plant growth. These three major nutrients are always in the same order: Nitrogen-Phosphorus-Potassium (N-P-K). Each of these nutrients affects plant growth differently.


The first number represents Nitrogen, which provides plants with the ability to produce chlorophyll and promotes growth to the foliage. In proper amounts, plants grow taller and greener with each additional nitrogen application.


The second number represents Phosphorus, which aids in root development and helps increase the size and number of blooms. A fertilizer high in phosphorus content helps plants "root in" more quickly. If you have plants that have not been blooming well, consider using 0-30-0 or 0-45-0 to boost root growth and bloom production.


The third number represents Potassium, which has many functions. It helps plants resist diseases and aids in tolerance of drought and cold. It also improves root development, strengthens stems, and helps with photosynthesis.

When You Plant

Incorporate a complete fertilizer like 10-10-10 into the soil at the time of tilling or planting.

After You Plant

For maximum growth, a high nitrogen fertilizer like 16-4-8 should be applied every 4-6 weeks after planting, beginning in early spring through late summer. In early fall and winter, apply at half (or less) the recommended rate to avoid stimulating top growth that might be harmed by winterburn.

After Use Care

* After fertilizing, water the plants to wash fertilizer from foliage and avoid any burning of new growth.
* Avoid over-fertilizing, it can burn or even kill your plants. Fast growing plants and plants that produce an abundance of blooms can benefit from more fertilizer.

Determining Fertilizer Needs

Professionals can often recognize a plant's need for a particular nutrient by simply looking at the foliage. For example, if the foliage is turning light green or yellow, this may indicate an iron or nitrogen deficiency or perhaps too much moisture around the roots. Purple foliage on an otherwise green plant might be a sign of phosphorus deficiency.

The best way to determine what fertilizer or nutrients a plant needs is having a soil test done. Most counties offer low or no cost soil tests through their Cooperative Extension Service. A soil test will indicate what nutrients are needed and can guide you to apply the correct amount and type of fertilizer. Alternatively, consider asking your local nursery or professional landscaper for an opinion as to what fertilizer might be best for your plants.

See also:
Cooperative extension services
Planting instructions

Back to: Ground preparation and fertilizing


Your privacy is important to us, we will not send you any unnecessary email. If you wish to be advised of our sales (2-4 times per year), join our mail list.