Many people suggest one should do a soil test, and principally I agree. On the other hand, I think I know what my soil lacks, better structure, a thicker layer of black soil and more earthworms. For that reason I save my money and study my weeds instead.

Perennial weed indicates how the soil was at the time when they established themselves. The annual weed indicates the actual state of the soil and environment much more accurately. One shouldn’t look for the most rare of the weeds in the garden, but concentrate on the major weeds as indicators.

At da.wikipedia.org I have found the table below. The translation is mine:

Ph is acidity, where 7 is neutral soil.
Lv is conductance. Salts, f.x. from NPK, increase the electric conductance of the soil.
Indicatorvalues shows the conditions statistically preferred by the specie. The number gives the placement on a nine-level scale, always shown in the same order: Light, temperature, seacloseness/continentality, moisture, acidity, nitrogen. If value is indicated by “x”, the species does not react on differences in this environmental factor.

Plantenavn pH lv soil type fertilizing Indicatorvalues
Viola arvensis low pH low lv low Ca-value 6; 5; x; x; x; x
Cirsium arvense Low humus content 8; 5; x; x; x; 7
Corn spurry < 6,5 low lv sandy, humusrich soil 6; 5; 3; 5; 3; 6
Viola tricolor < 6,5 sandy soil low P-value 7; x; x; 4; x; x
Sonchus oleraceus 6-7 7; 6; x; 4; 8; 8
Elytrigia repens low P- and Mg-values 7; 6; 7; x; x; 7
Deschampsia flexuosa low pH low lv low N-value 6; x; 2; x; 2; 3
Poa annua high lv high K-value 7; x; 5; 6; x; 8
Stellaria media high K-value 6; x; x; x; 7; 8
Plantago major humusrich soil 8; x; x; 5; x; 6
Artemisia vulgaris < 6,5 7; 6; x; 6; x; 8
Anemone ranunculoides) humusrich soil high N-values
Glebionis segetum < 6 7; 6; 2; 5; 5; 5
Calluna low N-value 8; x; 3; x; 1; 1
Erodium cicutarium < 7 low lv low humus
Hop v humusrich soil high N-value 7; 6; 3; 8; 6; 8
Chenopodium album low lv low Mg-value x; x; x; 4; x; 7
Anchusa arvensis sandy soil
Ranunculus repens high lv humusrich soil high Mg-value 6; x; x; 7; x; 7
Urtica urens 6,5-7 high N-value 7; 6; x; 5; x; 8
Myosotis arvensis < 6 low lv
Veronica arvensis < 7 low lv
Anagallis arvensis high pH high lv clay, humuspoor soil high Mg-value 6; 6; 3; 5; x; 6
Lamium purpureum high pH high lv claysoil high P-value
Rumex acetosella low lv sandy, limepoor soil low P-value 8; 5; 3; 3; 2; 2
Fallopia convolvulus low pH low lv humuspoor soil low K- and Mg-values
Solanum nigrum high pH high lv claysoil 7; 6; 3; 5; 7; 8
Urtica dioica humusrich soil high N-value x; x; x; 6; 7; 9
Veronica persica high pH high lv clay, humuspoor jord high Ca- and P-values
Atriplex patula high pH high lv claysoil
Polygonum aviculare humuspoor soil 7; 6; x; 4; x; 6

Table originates for dk.wikipedia.org

In my kitchen garden weeds are mainly Poa annua (7; x; 5; 6; x; 8), Ranunculus repens (6; x; x; 7; x; 7) and Stellaria media (6; x; x; x; 7; 8).

The mean values are as follow:
Light 6,3 half light plants 20-30% rl. (relative light intensity).

Temperature x, My weeds do not indicate anything about temperature.

Continentality 5, average.

Moisture 6,5, well moist, but not wet

Acidity 7, Only Poa annua indicate light acid to alcaline soil. Less common weeds in my garden indicate more alcalinity.

Nitrogen 7,7, light to more nitrogen rich soil.

There is also indication for richness of potassium and magnesium, and quite as important no indicator of low values of phosforus.

This analysis confirm my first asumption – my soil have a reasonalble content of fertilizing elements, and gives me no reason to invest in a chemical soil analysis.

Do you have a different oppinion, I sincerely hope you will leave a comment. Click on “comments” at the top of this post.