Fertilizer Basics

Garden Tip from Harry Thompson

01412 garden_fertilizer

Torrey Pines Landscape Co.




Torrey Pines Landscape Company specializes in landscape design, maintenance and custom installations including automatic irrigation and drip systems, lighting, fountains, decks, patios, barbecues and firepits.



Fertilizer keeps plants happy and healthy because this plant food contains three of the primary nutrients — nitrogen, phosphorous and potassium — your soil needs to keep your plants productive and beautiful. Nitrogen acts like protein and promotes healthy foliage, phosphorous stimulates root growth and potassium encourages big blooms. 


Every bag of fertilizer has a label with three numbers. The first number indicates how much nitrogen (N) is contained in the fertilizer, the second how much phosphorous (P205) and the third how much potassium (K20). This N-P-K ratio reflects the available nutrients by bag weight contained in the fertilizer. For example, a bag labeled 15-15-15 contains 15 percent nitrogen, 15 percent phosphorous and 15 percent potassium.


A fertilizer labeled for general purpose will keep most plants healthy, but the kind of fertilizer you choose will depend on what you are growing (tomatoes have different nutritional needs than flowers) and how much pH or acidity is in your soil and what type of soil you have. 


Special-purpose fertilizers are designed for specific needs such as making your lawn greener or stimulating bloom. Other fertilizers contain optimized proportions of the three main nutrients for particular kinds of plants like roses, citrus, succulents, palm and acid-loving shade plants. I suggest using Pat Welsh’s Southern California Gardening to dial you in on specialty plants. 


When you fertilize:

  • Make sure the ground is moist before you fertilize.
  • Wash granular fertilizer off leaves so they don’t get burned.
  • Water the fertilizer in as soon as possible, but preferably within a couple of hours after it is applied so that the fertilizer’s nitrogen doesn’t turn back into a gas and just vaporize into the atmosphere instead of going into the soil and being absorbed by the plants roots.
  • Use a fertilizer with higher nitrogen in the cooler months; use less nitrogen and more iron in the warmer months so you get green without excessive growth.
  • Make sure that if you are using a fertilizer with iron, the iron is a non-staining form to protect hardscape and pool plaster.
  • Make fertilizing your plants easier by using a good fertilizer spreader.

Categories: Gardening