Left: Anagallis arvensis, a weed that produces an advanced root system to ensure its survival; right: Datura stramonium, a vigorous weed that relies primarily on seed for reproduction.
A weed is defined in the most simple manner as a plant growing in an area where it is unwanted. This could apply to a garden, a farm, or any possible landscape where a plant may appear. Plants may be considered unwanted based on ornamental value or their competitiveness with desired plants. Plants within the same community often compete for water, nutrients, and physical space. Unfortunately, it is the weed that most often wins, followed by a reduction in crop yields and garden aesthetics. It is in these situations, that weed control is most often practiced.
Before we make an attempt at weed control, it is important for us to understand why the weed is so often victorious over the plants that we originally intend to grow. An ecological definition of the weed will bring us closer to an understanding: “Weeds are plants that are especially successful at colonizing disturbed, but potentially productive sites, and at maintaining their abundance under conditions of repeated disturbance” (Liebman, Mohler, and Staver, Ecological Management of Agricultural Weeds, 2001). Unlike the cultivated plants of the farm or garden, weeds have biologically adapted to these conditions over several generations to ensure survival. An example of this biological adaptation could be the size and structure of the seed or the the length of a tap root. Weeds with an annual or biennial life cycle primarily rely on seeding to spread. However, perennial weeds have highly developed root systems, in addition to seeding, that give them an advantage in spreading and creating new plants asexually. Knowing these characteristics helps us develop strategies for control.
In the past the gardeners at The Cloisters have relied primarily on the mechanical removal of weeds—hand weeding. Although this technique is effective, it is obviously the most time-consuming and labor intensive. This season we have been experimenting with steam as a means of weed control. We use a simple steam cleaner, which is the size of a vacuum. The results have been wonderful. If applied at the right time, the steam addresses both seed dispersal and the vigorous root systems of weeds. Not only is it effective, it has its roots in the Middle Ages, as mentioned in the earlier post, “Another Thistle”.