Tag Archives: fertilizers

Organic vs. Chemical Fertilizers, & Those 3 Numbers

You’ve seen the three numbers on fertilizers. This is called the chemical analysis or fertilizer analysis. Those numbers (and their chemical symbols) are, in order, nitrogen (N), phosphorus (P), and potassium (K). Gardeners often refer to potassium as “potash”. (Potash reminds me of a funny story which I will tack onto the end of this blog post.) The numbers represent the percentage of the product that is composed of each chemical. The numbers won’t add up to 100%. The remainder of the product is filler, including inert components that will aid in dispersing the chemicals.

You know I prefer organic fertilizers and pesticides.  So I will give you a list of good organic sources of these chemicals needed by all plants.


Boston Fern w Bud - mlm c

Nitrogen promotes lush green lawns, and beautiful leaves with strong stems. All plants need some nitrogen, but needs vary. Look to high-nitrogen fertilizers for turf grasses and foliage plants such as this fern.

The Best Sources of Nitrogen

  1. Composted Cow Manure — should be at least 6 months old.
  2. Composted Chicken Manure — should be at least 4 months old.
  3. Blood Meal — in order not to burn plants, dissolve in water before applying to plants, or work into soil before planting.
  4. Fish Emulsion — this can be very stinky, but is an excellent organic fertilizer. It can be diluted with water to weaken the odor.
  5. Coffee grounds — used coffee grounds are only about 2% nitrogen, yet they are a great soil amendment.


Moonflower - mlm c@

Phosphorous promotes strong, healthy roots and generates lush flowers and fruit production. If it’s lots of flowers, tomatoes, and other fruits that you want, look for a fertilizer that is high in phosphorous, i.e., look for a high middle number.

The Best Sources of Phosphorous

  1. Bone Meal — a great slow-release form of phosphorous and calcium, and my personal favorite.
  2. Banana Peels
  3. Crab and Shrimp shells — be aware the odor may offend your neighbors, and may attract critters to your compost bin. You can dry them, then grind them in a coffee grinder used only for this purpose and for grinding eggshells.
  4. Bat Guano — can be purchased.
  5. Fish Bone Meal — can be purchased.


Elephant Ear Swirls - mlm c

Potassium works on the inside of the plant, building strong cells and healthy tissues. This enables plants to withstand common plant stressors: diseases, pests, even heat and cold. All plants need potassium, but some need more than others. When shopping for plant foods, you will notice that those intended for winterizing lawns will have a higher number for potassium.

The Best Sources of Potassium

  1. Granite Dust (or Meal) — this is finely ground granite that is a great slow-release source of potassium. It also serves to maintain good soil drainage and to create good soil structure.
  2. Eggshells — Eggshells are primarily made of calcium carbonate, but they also contain potassium.
  3. Ashes of Hardwoods from Your Fireplace — while hardwood ashes are an excellent source of potash, they will also raise the pH levels of your soil, so be sure to keep a check on your soil’s pH levels. These days, you can buy a soil test kit at any garden center.
  4. Kelp (Seaweed) Meal — this can be in a dried and powered or liquid form. Both forms are fairly quick-release. Kelp meal can be purchased from many garden centers. If you live by the ocean, and can collect your own, lucky you.

Choosing the Right Fertilizer for Your Needs

Before spending money on fertilizers, think about which plants you will be using it on, and the specific needs of those plants. By choosing the individual organic compounds, you can target the needs of your plants much more accurately. I prefer this method over those large bags of (often synthetic) chemical fertilizers that may be good for one plant, but not so good for another.

The Funny Story I Promised

One of my uncles sent off a soil sample to one of the labs at Auburn University that will do these tests for you, for a fee, of course. When he received the results, he decided that he needed to be sure “those students” knew what they were doing, so he sent another sample. He intentionally added a large amount of ashes from his fireplace to the second sample. In about two weeks he received a brief note along with the soil analysis. Among other things, the note said, in bold print, “No more potash!” He then announced,  “Those kids know what they’re doing down there.”





Why Won’t My Hydrangea Bloom?

Amy N. told me about her hydrangea with lots of beautiful deep green leaves, and nothing else. Not a single flower. Nada. “Why won’t my hydrangea bloom?” she asked. I had a mental picture similar to the one below:

Hydrangea Leaves 2

After questioning her, and establishing that it gets the proper amount of shade vs. sun, is in good soil, and was covered during our last cold spell, I asked when she last pruned it. She had pruned it in the spring.

I suspect that is the problem, or at least part of the problem. Because the huge blossoms grow only on new growth, springtime pruning removes the flower buds that may not even be visible yet. Simultaneously, late winter pruning of old wood may cause the same problem because it is the old wood that carries the new stem and leaf buds from which the flower buds will emerge.

After asking if it is likely to outgrow it’s available space, and learning it has plenty of room to grow quite large, I suggested she not prune it at all. Of course, she may want a few blossoms to put into a vase in her home. After it blooms, she will need to remove any spent flowers in the late summer or fall. Removing spent blooms encourages more flowering.

I like to cut hydrangea flowers for indoor arrangements. Cut them when the flowers are at their peak, and they will last for weeks. They won’t wilt as most cut flowers do. Instead, they will gradually dry out, and make great dried flowers, too. The photo below is of some white Annabelles I grew in my yard in Alabama.

White Annabelles turn a lovely sage green as they dry.

White Annabelles turn a lovely sage green as they dry. This dried flower arrangement lasted about 6 months.

Another possibility for the lack of flowers could be too much nitrogen. Amy top-dressed her hydrangea with Black Kow. Composted cow manure has lots of nutrients, but is typically low in nitrogen, so that’s not likely to be the problem. It could be that any other fertilizer or plant food she may have used, or that may have been used on the lawn near the hydrange is too high in nitrogen for flowering shrubs.

Remember “NPK” the letters that are represented by the numbers on fertilizer bags? NPK stands for nitrogen (N), phosphorous (P), and potassium(K); and the numbers will always appear in that order. The numbers indicate the percentage of each nutrient that is present in the bag. Nitrogen produces very green grass, as well as more leaves and top growth on plants. Phosphorous produces more flowers and fruit, and strengthens root development. Potassium produces strong healthy plants.

A fertilizer numbered 26-3-3, or any combination with a larger amount of nitrogen is a good fertilizer for turf grass, but NOT for flowering plants. For flowers and flowering shrubs a fertilizer with a higher middle number (phosphorus) is needed.  Some examples of this are 15-30-15 and 5-30-5.

With tomatoes, too much nitrogen will produce lots of pretty leaves, but a less than normal amount of fruit. I suspect that is what’s going on with Amy’s hydrangeas.


White Lacecap and Purple Annabelle Hydrangea

Pink Annabelle Hydrangea

These pink Annabelle Hydrangea are beginning to change color because I’ve been sprinkling used coffee grounds around them. The more acidic the soil, the bluer they become.