Learning weeds by plant families is one of the best ways to learn identification.
Families often have common traits among different species that allow you to group weeds in
your mind for easier ID. These family characteristics are also very helpful to begin ID of
a new weed species.
Closely related to the plant family way of learning weed ID is the "species-group"
concept discussed previously. Many of our most successful weed
"species" are in fact a group of closely related, often inter-fertile, species.
Learning these weed species-groups will aid you in learning weed ID.
Plant Family ----> Species-Group ----> Species ----> Variants
poison ivy (Rhus radicans) woody perennial
common cocklebur (Xanthium strumarium) summer
annual
dandelion (Taraxacum officinale) perennial
horseweed (Conyza canadensis) summer annual
common sunflower (Helianthus annuus) summer
annual
The Thistle Species-Group:
Canada thistle (Circium arvense)
perennial
Biennial Thistles:
-bull thistle (Circium vulgare) biennial
-[musk thistle (Carduus nutans) biennial]
The Ragweed Species-Group:
common ragweed (Ambrosia artimeisiifolia) summer annual
giant ragweed (Ambrosia trifida) annual
hemp dogbane (Apocynum cannabinum) perennial
[bur cucumber (Sicyos angulatus) summer annual]
quackgrass (Elytrigia repens ) perennial
wirestem muhly (Muhlenbergia frondosa) perennial
[woolly cupgrass (Eriochloa villosa) summer annual]
barnyardgrass (Echinochloa crus-galli) summer
annual
volunteer corn (Zea mays) summer annual
[field sandbur (Cenchrus incertus) summer
annual, biennial]
[foxtail barley (Hordeum jubatum) perennial]
The Panicum Species-Group:
wild proso millet (Panicum miliaceum) summer annual
fall panicum (Panicum dichotomiflorum) summer annual
witchgrass (Panicum capillare) summer annual
The Foxtail Species-Group:
green foxtail (Setaria viridis) summer annual
bristly foxtail (Setaria verticillata) summer annual
giant foxtail (Setaria faberi) summer annual
yellow foxtail (Setaria glauca) summer annual
knotroot foxtail (Setaria geniculata) summer annual
The Crabgrass Species-Group:
large crabgrass (Digitaria sanguinalis) summer annual
smooth crabgrass (Digitaria ischaemum) summer annual
The Sorghum Species-Group:
shattercane (Sorghum bicolor) summer annual
johnsongrass (Sorghum halpense) perennial
sorghum-almum (Sorghum almum) summer annual
[The Bromegrass Species-Group]:
downy brome (Bromus tectorum) winter annual, summer annual
smooth brome (Bromus inermis) perennial
wild hemp, marijuana (Cannabis sativa; Cannabis indica) summer annual
common lambsquarters (Chenopodium album) summer
annual
[kochia (Kochia scoparia) annual]
[black medic (Medicago lupulina) annual, biennial, perennial]
[Sweetclover species-group:]
yellow sweet clover (Melilotus officinalis) annual, biennial, perennial
white sweet clover (Melilotus alba) annual, biennial, perennial
[purple loosestrife (Lythrum salicaria) perennial]
velvetleaf (Abutilon theophrasti) summer annual
[venice mallow (Hibiscus trionum) summer
annual]
common milkweed (Asclepias syriaca) perennial
[catnip (Nepeta cataria) perennial]
[ivy leaf morningglory (Ipomoea hederaceae) summer annual]
Bindweed species-group:
field bindweed (Convolvulvus arvensis) perennial
hedge bindweed (Calystegia sepium) perennial
field pennycress (Thlaspi arvense) winter
annual
shepard's purse (Capsella bursa-pastoris) summer
annual/winter annual
wild mustard (Sinapis arvensis) winter/summer
annual
jimsonweed (Datura stramonium) summer annual
The Nightshade Species-Group:
eastern black nightshade (Solanum ptycanthum) summer annual
bitter nightshade (Solanum dulcamara) summer annual
The Pigweed Species-Group
redroot pigweed (Amaranthus retroflexus) summer annual
smooth pigweed (Amaranthus hybridus) summer annual
Powell pigweed (Amaranthus powellii) summer annual
spiny pigweed (Amaranthus spinosus) summer annual
tumble pigweed (Amaranthus albus) summer annual
prostrate pigweed (Amaranthus blitoides) summer annual
common waterhemp (Amaranthus rudis) summer annual
tall waterhemp (Amaranthus tuberculatus) summer annual
Palmer amaranth (Amaranthus palmeri) summer annual
Plantain species-group:
Blackseed plantain (Plantago rugelii) perennial
Broadleaf plantain (Plantago major) perennial
Buckhorn plantain (Plantago lanceolata) perennial
purslane (Portulaca oleracea) summer annual
[multiflora rose (Rosa multiflora) perennial shrub
yellow nutsedge (Cyperus esculentus) perennial
The Polygonum Species-Group
-wild buckwheat (Polygonum
convolvulvus) summer annual
Knotweed Species-Group
-prostrate knotweed (Polygonum aviculare) summer annual
-erect knotweed (Polygonum erectum) summer annual
Smartweed Species-Group
-Pennsylvania smartweed (Polygonum pensylvanicum) summer annual
-ladysthumb (Polygonum persicaria) summer annual
-swamp smartweed (Polygonum coccineum) perennial
