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Reading Weeds














This is a discussion of terms used in the weed vignettes. Some of the terms are common adjectives but have specific meanings when used in the context of plant indicators and ecology. Numbers are used to show increasing level of the quality under consideration.

Not all of these characteristics are included in the vignettes. In the book these will be noted if there is information available.



Elements There are different types of qualities that are important in different situations:

indicator - the presence of this weed is often associated (but not always) with the given level of the element.

tolerates - The weed can grow with a high or low level of this element.

ratio of base saturation - The percentage of the binding sites on the soil that are occupied by this element.

indefinite or non-specific response - This weeds growth doesn't respond dramatically to high or low levels of this element.

accumulator - An element is actively concentrated in the plant tissue, higher than is usual for other plants growing in the same soil.

content indicates nutrient level - Some plants have nutrient levels in their tissues that reflect the amount is the soil.

pulls up from subsoil - Deep roots mobilize minerals and bring to above ground parts, which would be available to the next crop.

data - This is a small bit of data, not enough information to establish This plant as an indicator. This information may be useful but is not verified by a lot of information or experience.

reference - These notes are followed by a 4 digit number in parentheses that is the code for the literature reference. Anything not referenced can be considered the opinion of the author.


Nitrogen, N, nitrate, ammonia supply, description of levels:

1 only in soils very poor in mineral nitrogen

3 mostly in poor soil

5 mostly in intermediate soil

7 mostly in soil rich in mineral nitrogen

8 nitrogen indicator

9 only in soil very rich in mineral nitrogen, indicating pollution, manure deposits or a similar situation


Salt, Na, sodium

millimhos 1880

0 very sensitive

1 sensitive 3-2

3 mildly tolerant 6-3

5 tolerant, but more freq in non saline soil 12-6 I

7 facultative halophyte, mostly in saline soil II

9 obligatory halophyte, only in saline soil III


Water, soil moisture or water level

1 extremely dry soil, e.g. bare rocks

3 in dry soil

5 in fresh soil, intermediate conditions

7 in moist soils that do not dry out

9 wet soil, often not well aerated

10 frequently inundated soil


pH, acid and base

range description C20,0460 pH phytosocial

X - indifferent - 4-8 no definite response

1 - only very acid A <5 moderate to strong acido freq

2 -

3 - mostly acid a <5.5 weak to strong acido freq

4 -

5 - weakly acid b 5.0-6.0 weak to moderate basi freq

6 -

7 - neutral, also A & B 7

8 - 7.5

9 - only neutral or B B 5.2-7.5 moderate to strong basi freq

0 - basic >7 only on basic



Organic Matter

relative amount for low to high

or % if data available



Good soil is one part each rock particles, water and air. Soil life helps to maintain this balance. There are several ways that this balance can be destroyed. There is mechanical compaction, waterlogging, salt or alkali buildup, and poisons like herbicides.

surface compacted or crust

heavy machinery compaction

plow pan - A hard layer formed by the sole of the plow pushing down on the soil, 8 to 12 inches below the surface.

worked wet - causing clay soil plates to pack tightly together

dense - soil that for whatever reason is non-porous

loose, drains easily



Soil Classification

Verbal description of the soil textures and origins.







alluvial, glacial, etc


Habit and Control

Notes from ref. 4390, Weeds, unless otherwise indicated


Temp Average: average of monthly means in 'C (values below 0'C treated as 0) from ref 1694 unless otherwise indicated.


Temperature Figure

Description Altitude Latitude Mean Ann Biotemp

0 - very cold nival polar <1.5'C

1 - only in cold climate alpine subpolar P 1.5-3

2 - subalpine boreal B 3-6

3 - mostly in cool climate montane cool temperate C 6-12

5 - intermediate submontane warm temperate W 12-24

7 - mostly in warm climate

8 - premontane subtropical S

9 - only very warm climate mediterranean

10- tropical tropical T



Humidity Provinces mean annual rainfall in mm

description humidity T S W C B P

x - desert superarid 125- 125- 125- 125- <125

t - thorn perarid 250- 250- 250-

s - steppe arid 250-

v - very dry semiarid 500-

d - dry subhumid 1000- 500- 500- 125- <125

m - moist humid 2000- 1000- 1000- 500- 250- 125-

w - wet perhumid 4000- 2000- 2000- 1000- 500- 250-

r - rain superhumid >8000 >4000 >4000 >2000 >1000 >500


Continentality Figure

1 - euoceanic

2 - oceanic

4 - suboceanic

6 - subcontinental

8 - continental

9 - eucontinental



Rainfall in decimeters (dm),

dm X 4 = in, in X 1/4 = dm, dm X 100 = mm


Life Form from Raunkiaer

- according to position of buds during winter

P Phanerophyte, tree normally growing more than 5 m tall

N Nanophanerophyte, shrub or small tree, 0.5 - 5 m tall

Z Woody Chamaephyte, dwarf shrub

C Herbaceous Chamaephyte, herb with buds above ground

Chr C. reptantia, creeping

Chv C. velantia, dwarf bush

Chn C. vine

H Hemicryptophyte, buds near the ground

Hr H. rosulata, basal rosette

Hs H. scaposa, shaft

G Geophyte, buds within the soil, often with storing organs

Gb G. bulbosa, ground bulb

Grh G. rhizomata, ground rhizome

Gr G. radicigemma, root bud

T Therophyte, short lived "annual" plant

Ta T. aestivalia, summer annual

Th T. hivernalia, winter annual

Tb T. biannuellia, biannual

Te T. epeteia, in summer drought, overwintering annual

A Hydrophyte, aquatic plant with normally submerged buds

ep Epiphyte, attached to living plants

li Liana, rooting in the soil, but leaning on other plants

hp Half-Parasite, feeding on other plants, but with green leaves

vp Full-Parasite

s Saprophyte, feeding upon dead organic material

Syntax: Life form; Distribution type


Distribution Types (Feekes, from Sissingh)

V anemochoor, wind

H hydrochoor, water

A anthropochoor, man

Z zoochoor, animal

Au autochoor, self

capital - effective distribution over large distances

lower-case - rather efficient distribution over little distances

(letter) - little efficient distribution over very little distances


Leaf Green

I evergreen

W overwinering green

S summer green

V spring to summer green


Leaf Water

0 hy, hd hydromorphic, water plant

2 he helomorphic, with aeration tissue mainly in the underground organs

4 hg hygromorphic, with soft shadow leaves

6 m mesomorphic,

8 sk scleromorphic, with hard leaves and roots

9 su leaf succulent

A he & sk

B _________



Social, Phytosociological behavior

vegetation units in which the taxon is considered as character species, expressed by decimals. All info from ref 1880 unless otherwise indicated.

Gr group of classes (decimal because the number of classes is greater than 10)

K character species of a class or of a subordinate unit

O character species of an order or of a subordinate unit

V character species of an alliance

U character species of a suballiance

character species of associations have been omitted, because most of them are valid only locally

Syntax: Gr. K O V. U



1 full shadow plant, often receiving less than 1%, rarely greater than 30% of full sunlight

3 shadow plant

5 half shadow plant, more than 10%, but mostly less than 100%

7 half light plant

9 full light plant, rarely receiving less than 50%

() tree seedling in the undergrowth of forests



cw Common weeds of the US, (6405)

w Weeds, (4390)

jw Just weeds, (5760)

www Worlds Worst Weeds, (2811)




Spudding - digging out weeds with long tap roots with a long chistle like tool.

Harrowing - shallow surface cultivation with a spike-toothed harrow.

Disking - using a disk to cut and turn crops and weeds under the soil.