How to identify a weed

botanical descriptions can be obtained for weeds just as for turfgrasses. These keys use leaf, seed, flower, seedling and other important characteristics to assist in Identification. Two important stages for Identification is the seedling stage and the mature plant. If the greenkeeper can identify the weed at the seedling stage the weed is easier to control, as it has yet to reproduce itself and lie chemical rates may not be required. Experience is required for correct Identification.

The main character at this stage is the cotyledon shape and seedling morphology. The cotyledons or seed leaves are the first to be after termination and often are an opposite pair of leaves. For example, the group which includes Brassica rapa spp. campestris (Wild Turnip) and Sinapis avensis (Wild Mustard) the cotyledons are deep and round with an indent at the tip. The stalks are long.

The other forms are as follows:

Fathen (Chenopodium album)-cotyledons long and narrow, but less than five times as broad.

Dock's(Rumex spp.)-cotyledons long and narrow but usually less than five times as broad.

Thistles(Cirsium spp.)-first true leaves with long, stiff spines on the margins, cotyledons large, fleshy and stalkless.

A demonstartion of a key for turfgrass weed identification is found below.

KEY FOR THE INDENTIFICATION OF WEEDS IN TURF

Using the Key

This key has been prepared on the dichotomous system that is, they are always two opposing characters from which to choose.

For instance, the first step in using this key to identify a lawn weed, is to decide between the two "A" characters; in other words whether the leaves are"narrow, and are either flat and grass like, or oval in cross-section" or whether they are " flat and broad and sometimes divided into many lobes, but not grass like". Each of the sections is divided into two smaller sections depending on two opposing characters in the same manner.

The use of the key will be made easier by a little practice, while a number of diagrams of the leaves and other structures referred to in the key will assist in interpreting the terms..

During the winter months most metropolitan lowlands show a strong growth of a small pale green weedy grass which can become troublesome, particularly in a Couch lawn. The identification of this plant will illustrate the use of the key.

The plant has a slender grass like leaves, and by a comparison of the two "A" characters in the key it would clearly go on the the first "A". There are then two "B" characters to choose between, and as the leaves are not rounded or oval in cross-section, but are flat and grass like it would be placed in the first "B".

The two "C" paragraphs in this section relate to the growth habit of the plant-it may are either be present in the lawn all the year round, or it may be seasonal. The plant we are identifying is plainly seasonal, since it germinates after the winter commences, and it would go under the the first "C".

The final choice is then between plants which grow during the summer, and those which grow during the winter. Our plant is a winter grower, and this fact identifies it as Wintergrass (Poa annua). This Identification is verified by the other characters " stemless and forming small clumps, leaves pale green and hairless". The No. 1 refers to the fact that the first of the attached descriptions is one which gives further details of this plant.

    A.-leaves narrow, either flat and grass like, or oval in cross-section.

        B. Leaves flat and grass like.

            C.-plants short-lived, towing at the end of the season, and re-generating the following year from seed.

                D. Plants growing during the winter months. Stemless and forming small clumps. Leaves pale green and hairless.

                DD.-Plants growing during the summer, developing many stems which root at the joints. Leaves dark green, hairy.

    CC. Plants growing, and remaining green, during both summer and winter.

                D.-Plants forming clumps and not spreading by elongated stems.

                    E.-Leaves narrow, usually rolled, grey-green. Seed head elongated, narrow, resembling rat's tail. Growth mainly                       in winter.

                    EE.-leaves flat, broad, bright green. Growth mainly in summer. Seed-head green with several spreading branches.

            DD.-plants spreading by means of elongated above ground stems rooting at the joints, or by underground root like             stems sometimes deep in the ground and not at first sight apparent.

                    E.-Plants low, turf forming and growing amongst the lawn grass.

            F.-Leaves broad, resembling those off Buffalo grass, but less harsh and paler green.

                    G.-Plants spreading by means of above ground stems rooting at the joints. No underground stems. Leaves widely                       spaced on stem.

                    GG.-Plant spreading by both deep underground stems and above ground stems rooting at the joints. Leaves                       crowded on the stems.

            FF.-Leaves narrow, bright green in color; underground stems near the surface, and together with the bases of the                      upright stems covered with brown scales. Seed heads small, globular, green.

        EE.-Plants with erect growing leaves which rapidly project above the level of the mown lawn. Seed heads large, brown.

               F.-Underground stems thin, wiry, black and swollen form small "nuts" at intervals deep in soil.

               FF.-Underground stems thin nearer the surface, and covered with scales. No "nuts".

    BB.-Leaves oval in cross-section, erect in growing habit and projecting above the level of the lawn. Winter growing species.              Flowers red or mauve.