Shannon Hunt digs into her garden dictionary to help newbie gardeners clarify the meanings of commonly heard jargon used in the gardening community, especially round this time of year.
The word ‘chemical’ is easy to misinterpret when applied to gardening and soil care because, while we may associate it with manmade synthetic fertilisers, it also describes many processes that occur biologically in our soil. A good example of a soil chemical reaction might be how nitrogen (a gas) is absorbed from the atmosphere into the soil as a gas that cannot be absorbed by plants, so it is ‘chemically’ changed by the soil microbes into nitrate form that plants can take up.
In simple terms a plant is dormant when it shuts down over a specific season and stops producing leaves, flowers or seeds to get it through adverse conditions. In New Zealand this is usually over the colder months. Plants do this to survive, and roses are a good example of this process, as are willow trees and fruit trees. As the weather and soil begins to get warmer in late winter and spring, these plants will break their dormancy and new growth will begin so the plants can then produce flowers and fruits.
These three letters stand for the three macronutrients that all plants need to live: nitrogen (N), phosphate (P) and potassium (K). NPK is a rating that appears on all commercially produced synthetic fertiliser products to show what quantity of each macronutrient is in the product. Natural, organic fertilisers don’t usually show just an NPK rating, but instead often show a full table of the amounts of macronutrients and equally important micronutrients that are in the product.
Nitrogen helps to build proteins in plants and plays a large part in a plant’s making of food, via photosynthesis.
Phosphates help to create strong root systems so a plant can take up nutrients well.
Potassium assists with reproduction (flowering) of a plant, and it plays an important part in a plant’s overall wellbeing and survival.
Why is ‘K’ the symbol for potassium? The dictionary says the name potassium is derived from the English pot ash (potassium carbonate). The chemical symbol K comes from the word ‘kalium’, mediaeval Latin for potash and bestowed in 1797 by the German chemist Martin Heinrich Klaproth to distinguish potash from soda (sodium carbonate). Germanic countries still refer to kalium rather than potassium.
These are chemically created, manmade fertilisers, that usually only contain nitrogen, phosphate and potassium, although they can sometimes include other additives. A simplified description of synthetic fertilisers is ‘they tend to feed a plant directly over a quick, short period of time’, while biologically sourced, organic fertilisers feed the beneficial micro-organisms that improve soil content and structure (so plants can take up natural nutrients) over a longer, slower period of time.