Weed life history: identifying vulnerabilities - Ecological Management of Agricultural Weeds - page 43

Table 2.2. Four types of weed life-history strategies

Character Annuals Stationary perennials Wandering perennials Woody perennials

Vegetative life span 1 year 2 to a few years Long,indefinite Long

Vegetative propagation No Accidental Yes Some species

Usual seed persistence Years to decades Years to decades Afew years Months to years

Energy allocated to seed production High Medium high Medium low Low

Seed size a Mostly small Mostly small Mostly small Mostly large

Usual mode ofestablishment Seeds Seeds Vegetative propagules Seeds

Main dispersal modes With soil,manure With soil,wind,feces,crop With soil Birds,wind

seed

Position in succession Year 1 (2 in gaps) Year 1 to 5 (10) After year 1 Middle

Taxonomy Monocot and dicot Mostly dicot Monocot & dicot Mostly dicot

Crop types Annual Forage,annual All Orchard,pasture,swidden,no-till

Examples Chenopodium album Rumex crispus Imperata cylindrica Lantana camara

Setaria faberi Poa annua b Convolvulus arvensis Toxicodendron radicans

Notes:
a Seed size ranges and medians from an analysis of39 annual,18 stationary perennial,and 16 wandering perennial British weed species ofarable land and
well-drained grassland reported in Salisbury (1961) were 0.02-35 (1.1),0.2-3 (1.2) and 0.13-14 (0.7) mg,respectively,indicating no difference in seed size
between the three categories.
b Because Poa annua sets seed during its first season oflife,it can behave as an annual in annual cropping systems.However,ifleft undisturbed it usually lives
at least two seasons,and often sets more seed the second year (Law,Bradshaw & Putwain,1977).