Gardening Tips: May 21, 2014

Inorganic fertilizers
The past week’s rain arrived at a perfect time to allow most of our gardens, landscape plantings and lawn to develop their foliage. (Weeds too!) The showers and thunderstorms will sometimes put a temporary damper on outdoor work, but we do need some rain every few days to fuel the new growth. Yard cleanup is in full gear by now as we prepare for the upcoming growing season in earnest. I have finally harvested enough asparagus for a few meals this past week, much to my stomach’s delight! Freshly harvested asparagus is a wonderful treat and one of the only two perennial vegetables we can grow here. Guess the other one! (answer next week)
This is the time of year we routinely apply fertilizer to our gardens and lawns, but this process is not nearly as simple as it was years ago. I recently stopped at Story’s nursery in Freehold and I was surprised at the variety of different types of fertilizers for sale. There must have been more than two dozen different products for sale and I could see how a novice gardener might be overwhelmed by the selection. Not too many years ago, choices were limited to a very few products but now there are so many that I am writing this to provide some explanation.

Types of fertilizers
There are basically two types of fertilizers and two ways that they are marketed. “Complete” fertilizers all must contain nitrogen, phosphorus and potassium. These three nutrients are often required as an annual application, since they tend to be either used up by the plants or washed out (leeched) from the soil every year. The percentage by weight of each of these is listed on the label of the product and they are always listed in that specific order, i.e. N, P, and K. (K stands for potassium). A 100-pound bag of 5-10-10 has five pounds of Nitrogen as well as 10 pounds each of phosphorus and potassium. The other type does not contain all three of these elements, but the elements that it does contain must also be listed in the exact same order, i.e. 0-0-20 or 0-5-10 or 5-0-0. The higher the total numbers listed, the more fertilizer in the package. A 100-pound bag of 20-20-20 contains double the nutrients of a 100-pound bag of 10-10-10. Consequently, it should cost double the amount, since you are paying for fertilizer and not “inert” ingredients such as sand or kitty litter. As it turns out however, that is rarely the case!
Most “specialty” fertilizers cost far more than generic products. Oftentimes, a lot more! I have seen a liquid fertilizer for sale at about $10 a pint, which has an analysis of 0-0-0.5, which means you are paying $10 for 99.5 percent water. Right next to it on the shelf, at a lower price, is a liquid product with an analysis of 10-15-10, which is 35 percent nutrients and only 65 percent water. You may be wondering why anyone would pay so much more? Well, the answer is a bit complicated, but part of it has to do with convenience and ease of application. A very dilute fertilizer can be applied without fear of overdoing it or possibly burning the plant. It is pretty easy to over apply a 20-20-20 product compared to a 1-1-1 product. Some people think that if “a little is good, than more is better.” This is surely not the case with fertilizers or pesticides either for that matter.

What they are for
The very expensive fertilizer I mentioned above has a picture of a cactus on the package. As it turns out, most cacti require very, very little fertilizer in most cases, so this product may be just fine for feeding them without risking an overdose. Other products are formulated for specific plants such as “Rose Food” or “Tomato Food” or “Orchid Food”. Will these products really work better on these specific types of plants? Generally not, as there is really very little difference in a 23-16-17 product compared to a 20-20-20 product.
Lawn fertilizers are formulated to have far more nitrogen that P or K and this makes sense because lawn grasses are constantly being cut. Nitrogen is the nutrient that is being used up fastest since it fuels grass and other green tissue growth. Plants that produce fruit, such as tomatoes don’t need that much nitrogen and over applying it may actually delay the tomato ripening process.

The specifics
Other fertilizers are designed for specific types of plants that require acid soil. They usually contain sulfur, which will acidify the soil for plants such as blueberries, rhododendrons and azaleas. The sulfur will be in some form such as Ammonium sulfate or iron sulfate.
Finally, some fertilizers are formulated to deliver the nutrients slowly over time. The fertilizer prills, or individual particles are coated with something that allows them to dissolve slowly over a period of time. Osmocote is one of the most well known time release products and it is indeed very handy when fertilizing plants in containers. A single application may allow you to not need to reapply every few weeks when watering.
Next week, I will discuss organic fertilizers.