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Understanding weed life cycles

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A weed is defined as a plant out of place, or a plant growing where it is not desired. Weeds compete with turfgrasses for light, water, soil nutrients and space. In a turf, weeds disrupt uniformity and are often considered to be aesthetically unpleasing. With a few exceptions, weeds will not provide year-round vegetative cover. A year-round turf cover is especially beneficial to prevent erosion and runoff, and in areas that might receive moderate to heavy use during the non-growing season. Weeds in athletic fields can adversely affect playability and athlete safety.

Weeds of turf are most often categorized by their life cycle. The most important thing one can learn about a specific weed is its life cycle. Knowledge of the life cycle is valuable when attempting to manage a specific weed because not all strategies are appropriate for all life cycles. Also, the timing of when a specific control strategy is implemented will vary based on a weed’s life cycle. A weed can be a summer annual, winter annual, biennial or perennial (Tables 9 and 10).

Annual weeds

Annual weeds reproduce by seed and complete their life cycle in one year. The annual life cycle is further divided into summer annual weeds and winter annual weeds. Summer annual weeds germinate in spring or early summer, grow vegetatively, flower and produce seed and die in late summer or fall. Examples of summer annual weeds include crabgrass, yellow foxtail, goosegrass, barnyardgrass, ragweed, purslane, spotted spurge, pigweed, carpetweed and prostrate knotweed. Winter annual weeds germinate in late summer and fall. They grow vegetatively and go dormant with the arrival of cold weather. In the spring they continue to grow vegetatively early and then switch to a reproductive phrase during which they flower and produce seed. After flowering, they die with the onset of warm weather. Winter annual weeds can be just as problematic and troublesome as summer annual weeds. Examples of winter annual weeds include shepherd’s-purse, common chickweed, sticky chickweed, annual bluegrass, henbit, pineappleweed, spring whitlowgrass and corn speedwell.

Biennial weeds

Biennial weeds reproduce by seed and complete their life cycle in two years. Biennial weeds germinate in spring to early summer and grow vegetatively forming a leaf rosette at the end of the first growing season. After over-wintering as a rosette, the biennial weed resumes growth, flowers, produces seed and completes the life cycle in the second growing season. Examples of biennial weeds are common mullein, burdock, bull thistle, wild carrot and garlic mustard.

Perennial weeds

Perennial weeds live for three or more years and reproduce by seed and vegetative propagules including roots, rhizomes, stolons, tubers, and bulbs. Dandelion, broadleaf plantain, narrowleaf plantain, broadleaf dock, false dandelion, spotted cat’s ear and fall dandelion are examples of simple perennials and reproduce by seed. Spreading perennials reproduce by seed and vegetative propagules and can form sizable clonal patches in turf. Examples of spreading perennials are quackgrass, red sorrel, creeping woodsorrel, Canada thistle and ground ivy. Other perennials such as wild garlic and star-of-bethlehem arise from bulbs. Yellow nutsedge arises from small tubers called nutlets.

Table 9. Life cycles of common broadleaf turf weeds

Common name Scientific name Life cycle
alyssum, hoary Berteroa incana perennial
bedstraw, catchweed Galium aparine winter annual
bedstraw, smooth Galium mollugo perennial
beggarticks, devil’s Bidens frondosa summer annual
bittercress Cardamine hirsuta winter annual
bittercress, cuckoo Cardamine pratensis perennial
bluets Houstonia caerulea perennial
buttercup, bulbous Ranunculus bulbosus perennial
buttercup, creeping Ranunculus repens perennial
carpetweed Mollugo verticillata summer annual
carrot, wild Daucus carota perennial
cat’s ear Hypochaeris radicata perennial
celandine, lesser Ranunculus ficaria perennial
chickweed, common Stellaria media winter annual
chickweed, mouse-ear Cerastium vulgatum perennial
chickweed, sticky Cerastium viscosum winter annual
chicory Cichorium intybus perennial
cinquefoil, old field Potentilla simplex perennial
cinquefoil, silvery Potentilla argentea perennial
clearweed Pilea pumila summer annual
clover, alsike Trifolium hybridum perennial
clover, rabbitfoot Trifolium arvense summer annual
clover, red Trifolium pratense perennial
clover, white Trifolium repens perennial
common lambsquarters Chenopodium album summer annual
copper-leaf, rhombic Acalypha rhomboidea summer annual
daisy, oxeye Chrysanthemum leucanthemum perennial
dandelion Taraxacum officinale perennial
dandelion, fall Leontodon autumnalis perennial
deadnettle, red Lamium purpureum winter annual
deptford pink Dianthus armeria perennial
dock, broadleaf Rumex obtusifolius perennial
dock, curly Rumex crispus perennial
evening primrose, common Oenothera biennis biennial
fleabane, annual Erigeron annuus winter annual/biennial
fleabane, poor-robin Erigeron pulchellus perennial
galinsoga, hairy Galinsoga ciliata summer annual
garlic, wild Allium vineale perennial
ground ivy Glechoma hederacea perennial
groundsel, common Senecio vulgaris summer annual
hawksbeard, narrowleaf Crepis tectorum summer annual
hawkweed, orange Hieracium aurantiacum perennial
hawkweed, yellow Hieracium pretense perennial
healall Prunella vulgaris perennial
hedge bindweed Calystegia sepium perennial
henbit Lamium amplexicaule winter annual
horseweed Conyza canadensis winter annual
jimsonweed Datura stramonium summer annual
knawel Scleranthus annuus winter annual
knotweed, prostrate Polygonum aviculare summer annual
maiden pink Dianthus deltoids perennial
mallow, common Malva neglecta annual/biennial
medic, black Medicago lupulina annual
moneywort Lysimachia nummularia perennial
mouse-ear cress Arabidopsis thaliana winter annual
mugwort Artemisia vulgaris perennial
nightshade, eastern black Solanum ptycanthum summer annual
pearlwort, birdseye Sagina procumbens perennial
pepperweed, virginia Lepidium virginicum summer or winter annual
pigweed, prostrate Amaranthus lividus summer annual
pigweed, redroot Amaranthus retroflexus summer annual
pimpernel, scarlet Anagallis arvensis summer annual
pineappleweed Matricaria matricariodes winter annual
plantain, broadleaf Plantago major perennial
plantain, narrowleaf Plantago lanceolata perennial
pokeweed, common Phytolacca americana perennial
purslane, common Portulaca oleracea summer annual
pussytoes, field Antennaria neglecta perennial
ragweed, common Ambrosia artemisiifolia summer annual
ragweed, giant Ambrosia trifida summer annual
rocket, yellow Barbarea vulgaris biennial
sandspurry, red Spergularia rubra summer annual
shepherd’s-purse Capsella bursa-pastoris winter annual
smartweed, ladysthumb Polygonum persicaria summer annual
smartweed, Pennsylvania Polygonum pensylvanicum summer annual
sorrel, red/sheep Rumex acetosella perennial
sowthistle, annual Sonchus oleraceus summer annual
sowthistle, perennial Sonchus arvensis perennial
sowthistle, spiny Sonchus asper summer annual
speedwell, common Veronica officinalis perennial
speedwell, corn Veronica arvensis winter annual
speedwell, purslane Veronica peregrina winter annual
speedwell, thymeleaf Veronica serpyllifolia perennial
spurge, spotted Euphorbia maculata summer annual
star-of-bethlehem Ornithogalum umbellatum perennial
stitchwort Stellaria graminea perennial
strawberry, wild Fragaria virginiana perennial
thistle, Canada Cirsium arvense perennial
thymeleaf sandwort Arenaria serpyllifolia winter annual
toadflax, oldfield Linaria canadensis summer annual
toadflax, yellow Linaria vulgaris perennial
tower mustard Arabis glabra biennial
trefoil, birdsfoot Lotus corniculatus perennial
velvetleaf Abutilon theophrasti summer annual
violet, wild Viola spp. perennial
white cockle Silene alba perennial
whitlowgrass, spring Draba verna winter annual
woodsorrel, creeping Oxalis corniculata perennial
yarrow Achillea millefolium perennial
yellow woodsorrel Oxalis stricta perennial

Table 10. Life cycles of common grass and grass-like turf weeds

Common name Scientific name Life cycle
barnyardgrass Echinochloa crus-galli summer annual
bentgrass, creeping Agrostis stolonifera perennial
bluegrass roughstalk Poa trivialis perennial
bluegrass, annual Poa annua winter annual/perennial
bluegrass, bulbous Poa bulbosa perennial
brome, downy Bromus tectorum winter annual
crabgrass, smooth or small Digitaria ischaemum summer annual
crabgrass, large or hairy Digitaria sanguinalis summer annual
fescue, tall Festuca arundinacea perennial
foxtail, giant Setaria faberi summer annual
foxtail, yellow Setaria glauca summer annual
goosegrass Eleusine indica summer annual
lovegrass, purple Eragrotis spectabilis perennial
nimblewill Muhlenbergia schreberi perennial
nutsedge, yellow Cyperus esculentus perennial
orchardgrass Dactylis glomerata perennial
panicum, fall Panicum dichotomiflorum summer annual
paspalum Paspalum setaceum perennial
quackgrass Elytrigia repens summer annual
rush, path Juncus tenuis perennial
sandbur, longspine Cenchrus longispinus summer annual
stiltgrass, Japanese Microstegium vimineum summer annual
stinkgrass (lovegrass) Eragrostis cilianensis summer annual
timothy Phleum pratense perennial
witchgrass Panicum capillare summer annual
zoysiagrass Zoysia japonica perennial