What is a weed? The most basic thing you ought to know

To my knowledge there is no botanical definition of a "weed". Instead, one may adopt a practical description of what constitutes one. First of all, let's establish what a weed is not. In gardening terms, two kinds of plants can be distinguished. One kind is the ornamental species used in parks and gardens, the other type is the wild plants that are generally not seen or planted in gardens.
A common habit is to group the latter together under the description "weeds", while conversely, the former are not weeds. This is synonymous with terming ornamental species as "good" and plants that grow in natural eco-systems, as "bad". Of course many people, especially ecologically minded ones, would object to such a description on principle. Putting principle aside however, a simple examination will show that this definition, it would be more appropriate perhaps to describe it as an attitude, is absurd in practical terms. How is that?

Let's take for example a private garden in a warm dry climate comprising of a lawn, hedging shrubs, a shade tree, a fruit tree or two, an area covered with creeping plants, and a small flower bed. All the species and varieties have been carefully chosen as part of an overall design. All the plants are therefore "good". But what happens if the lawn starts spreading into the flower bed, and becomes difficult to control? Is still "good"? On the other hand, one of the trees, a magnificent specimen in itself, disperses seeds that germinate in the lawn. As these start developing into trees themselves, are they now to be described as "good" or as "bad"? If developing the garden along the lines of the design is considered to be important, then they should be termed "bad".

Expanding on this line of argument, let's imagine that this family plot lies in the middle of a nature reserve. While according to the (imaginary) leasing agreement, the family has the right to plant as they wish in their own garden, the nature reserve authorities, are struggling to re-establish the natural flora of the area. It is no secret of course, that the state of the flora affects the condition of the natural fauna. In any eco-system, certain animal species are dependent on the presence of certain plant species, and vice versa. Now what's liable to happen if the "good" plants in the family garden, spread into the nature reserve surrounding the family property, and in the course of time start colonizing areas and thus cause the gradual elimination of some of the natural plants. The delicate balance is affected, resulting in the reduction and in worse cases, the elimination of animal species which had hitherto existed in association with the flora. Are our ornamentals still "good". In terms of the nature reserve they are arch criminals!

So ornamental versus wild, or beautiful versus ugly, can never serve as the basis for describing a certain plant as a weed or otherwise. The correct starting point is that any plant woody or herbaceous, cultivated or wild, pretty or miserable, a plant that enhances the design, or one that detracts from it, any plant can become a weed if it grows, or is liable to grow where it is unwanted and in such a way as to become difficult and in some cases, impossible to keep under control.

Jonathan@dryclimategardening.com