Cool-Season Weeds

September 19, 2018



Bittercress (Cardamine spp.)

Bittercress makes an early spring appearance, often sprouting before all danger of frost has passed. It’s also known as shotweed due to exploding seed capsules, which fling seeds far and wide. Mild winters and wet springs provide ideal growing conditions. Hand-pull if just a few; apply pre-emergent herbicide in fall to foil seed sprouting. Otherwise, keep bittercress mowed to prevent seeds from forming and shooting all over the yard.





Catchweed Bedstraw (Galium aparine)
Square stems and whorled leaves make bedstraw an unusual-looking weed. This annual weed tends to form long, lanky stems that sprawl in dense shade beneath trees and shrubs or alongside buildings. Stems have fine hairs that attach to other stems, clothing and fur. Flowers resemble white stars. Pull plants as you spot them and definitely once they start blooming.







Chickweed (Stellaria media)
Moist shade gives chickweed a just-right spot to grow and thrive. This ground cover weed is an annual that grows like a perennial in areas with mild winters. Stems root as they crawl along soil. Starry flowers open white. If left to set seed, you can expect 2,500 to 15,000 seeds per plant. Roots are fibrous and shallow. Plants tend to form mats that pull up easily following rains.







Common Plantain (Plantago major)
Paddle-like leaves hug the ground on this perennial weed. Plants produce both a short taproot and fibrous roots. Wait for moist soil, and plantain pulls readily. Seed heads form that are upright and almost beaded in appearance. Plants are adaptable, growing readily in moist or dry soil, sun or shade.








Curly Dock (Rumex crispus)
Watch for long leaves with curled edges that appear in lawns, garden beds and areas where soil has recently been disturbed. Flower stalks soar above leaves 24 to 36 inches. Flowers fade to form hundreds of shiny brown seeds. If seeds drop into soil, they remain able to germinate for 50-plus years. This perennial weed is a tough one. Dig plants when young, taking care to remove all of the taproot.






Dandelion (Taraxacum officinale)
This familiar face is the bane of lawns coast to coast. Toothed leaves form a ground-hugging rosette. Bright yellow flowers fade to puffball seed heads. Dandelion is a perennial weed. Dig or spot-spray if you only have a few offenders. Apply pre-emergent herbicide to lawns in fall to interrupt seed germination.








Flowering Sowthistle (Sonchus oleraceus)
The flowers on this weed resemble miniature dandelion flowers, which fade to form puffball seed heads. Leaves have prickly edges, but the rest of the plant is smooth. Stems bleed milky sap when broken. Pull young plants when soil is moist to remove the entire taproot.








Garlic Mustard (Alliaria petiolata)
Invasive and unwelcome, garlic mustard is overtaking native plant species in moist, shady settings. Plants are biennials. The first year, a leafy tuft of triangular, toothy-edged leaves appears. In the second year, white flowers on tall stalks emerge. Focus energy on pulling plants with flower stalks before they set seed. Attack leafy tufts later in the season.







Ground Ivy (Glechoma hederacea)
Also known as creeping Charlie, this perennial weed first appeared in landscapes as an ornamental ground cover. The plant’s fast growth soon shifted it to a weed category. Plants spread by both above and underground stems, as well as by flowers that set seeds. Ground ivy grows in sun, but is at its best in shade. Eradication requires a combined effort of hand-pulling and weed killers.






Henbit (Lamium amplexicaule)
Pretty purple flowers decorate on this annual weed in early spring, providing early-season nectar for pollinators. Square stems reveal this weed belongs to the mint family. Plants reproduce by seed, but can also root from stem pieces. Hand-pull when soil is moist.









Prostrate Knotweed (Polygonum aviculare)
This ground-hugging knotweed first sprouts in early spring and quickly grows to form a mat. A single plant can grow 2 feet or more across. You’ll likely overlook the flowers; they’re pretty small. Knotweed grows in compacted soil, often filling in areas of lawn where kids usually play. Hoe weeds as soon as you spot them in spring.







Purple Deadnettle (Lamium purpureum)
Plants often start growing in fall and complete their life cycle after resuming growth the following spring. Purple flowers start opening in spring and continue through the year. The early spring blooms help fuel pollinators. Watch for this weed in planting beds, veggie gardens and along lawn edges. A single plant yields 27,000 seeds. Hand pull this weed when you spot it to curtail its spread.






White Clover (Trifolium repens)
Some gardeners welcome clover for its nitrogen-fixing properties. Others consider it a nuisance and want it gone. This is a perennial weed that spreads rapidly by stems that creep both above and underground. You can hand-pull if you just have a few. Many homeowners spot spray plants in lawns with herbicide that kills weeds, not grass.

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