Annual weeds are plants that complete their life cycle—from germination to seed production and death—within one year. They can be classified into summer annuals and winter annuals based on their growing seasons. Here are some common examples:
Summer Annual Weeds
Summer annual weeds germinate in the spring or early summer, grow during the warmer months, and produce seeds before dying in the fall.
Common Ragweed (Ambrosia artemisiifolia)
Ambrosia artemisiifolia, with the common names common ragweed, annual ragweed, and low ragweed, is a species of the genus Ambrosia native to regions of the Americas.
It has also been called the common names: American wormwood, bitterweed, blackweed, carrot weed, hay fever weed, Roman wormwood, short ragweed, stammerwort, stickweed, tassel weed.
Description: Has deeply lobed leaves and produces small greenish flowers that turn into burr-like seeds.
Habitat: Found in disturbed soils, fields, and roadsides.
Lambsquarters (Chenopodium album)
Chenopodium album is a fast-growing annual plant in the flowering plant family Amaranthaceae. Though cultivated in some regions, the plant is elsewhere considered a weed. Common names include lamb’s quarters, melde, goosefoot, wild spinach and fat-hen, though the latter two are also applied to other species of the genus Chenopodium, for which reason it is often distinguished as white goosefoot.Chenopodium album is extensively cultivated and consumed in Northern India, and Nepal as a food crop known as bathua.
Description: Upright plant with mealy-textured leaves, often with a whitish coating on the underside.
Habitat: Grows in gardens, fields, and disturbed areas.
Pigweed (Amaranthus spp.)
Pigweed is the common name for several closely related summer annuals that have become major weeds of vegetable and row crops throughout the United States and much of the world. Most pigweeds are tall, erect-to-bushy plants with simple, oval- to diamond-shaped, alternate leaves, and dense inflorescences (flower clusters) comprised of many small, greenish flowers. They emerge, grow, flower, set seed, and die within the frost-free growing season.
Description: Broad-leaved plants with small greenish or reddish flowers; includes species like redroot pigweed and smooth pigweed.
Habitat: Common in agricultural fields and disturbed soils.
Crabgrass (Digitaria spp.)
Crabgrass, sometimes called watergrass, is a warm-season annual grassy weed that is prevalent in Iowa. Crabgrass germinates in the spring once soil temperatures hit 55°F for four straight days and nights, and will die with the cooler weather and frost in the fall. Iowa has both Digitaria ischaemum (smooth crabgrass, smooth hairless stems with hairs where the stem and leaf meet) as well as Digitaria sanguinalis (large crabgrass, the stems and leaves contain hairs).
Description: Grass-like plant with long, slender stems that root at the nodes; has finger-like seed heads.
Habitat: Found in lawns, gardens, and agricultural areas.
Foxtail (Setaria spp.)
Description: Grass with bristly, cylindrical seed heads; includes species like giant foxtail and green foxtail.
Habitat: Common in fields, gardens, and waste areas.
Winter Annual Weeds
Winter annual weeds germinate in the fall, overwinter as seedlings, grow during the spring, and produce seeds before dying in early summer.
Chickweed (Stellaria media)
Description: Low-growing plant with small, star-shaped white flowers and smooth, oval leaves.
Habitat: Common in gardens, lawns, and moist, shaded areas.
Henbit (Lamium amplexicaule)
Description: Square-stemmed plant with scalloped leaves and small, pink to purple flowers.
Habitat: Found in gardens, lawns, and disturbed soils.
Hairy Bittercress (Cardamine hirsuta)
Description: Small plant with pinnately divided leaves and tiny white flowers.
Habitat: Grows in gardens, lawns, and moist areas.
Shepherd’s Purse (Capsella bursa-pastoris)
Description: Plant with triangular, purse-like seed pods and small white flowers.
Habitat: Common in disturbed soils, gardens, and roadsides.
Annual Bluegrass (Poa annua)
Description: Low-growing grass with soft, light green leaves and a tufted growth habit; produces small, spike-like seed heads.
Habitat: Found in lawns, gardens, and golf courses.
What herbicides can be used to kill these weeds?
The common type of herbicide used to remove Annual weeds is Contact herbicides. (What is a contact herbicide?)
Contact herbicides are a specific type of herbicide that kill only the parts of the plant they come into direct contact with. They do not move (translocate) within the plant to reach other parts such as roots or shoots. As a result, these herbicides are most effective on annual weeds and less effective on perennial plants with extensive root systems.
Examples of Contact Herbicides
Paraquat:
Mode of Action: Inhibits photosynthesis by producing reactive oxygen species that cause cell membrane damage.
Uses: Widely used in agriculture for weed control in various crops and non-crop areas. It is highly effective but highly toxic, requiring careful handling.
Diquat:
Mode of Action: Similar to paraquat, it disrupts photosynthesis and causes rapid cell membrane damage.
Uses: Used for desiccation of crops before harvest, in aquatic weed control, and in industrial vegetation management.
Pelargonic Acid:
Mode of Action: Disrupts cell membranes causing leakage and rapid cell death.
Uses: Common in organic farming and gardening for control of broadleaf and grassy weeds. It is less toxic to humans and animals compared to synthetic contact herbicides.
Usage:
Contact herbicides are used for quick, effective control of annual weeds.
They are often employed in situations where immediate weed control is needed, such as in pre-harvest applications or to clear fields before planting.
They are also used in non-crop areas like industrial sites, along roadsides, and in urban settings where complete vegetation control is desired.
Speed of Action:
These herbicides often act quickly, with visible symptoms appearing within a few hours to a few days after application.
Rapid desiccation and death of the contacted plant parts are common.
Mode of Action:
Contact herbicides work by damaging or destroying the plant tissues they touch. The disruption occurs typically through membrane disruption, inhibition of photosynthesis, or disruption of other cellular processes.
Advantages:
Quick Action: Rapidly eliminates visible weeds.
Immediate Results: Useful for situations needing immediate weed removal.
Minimal Soil Residue: Often do not persist in the environment, making them a good choice for pre-planting weed control.
We are a weedkiller supplier based in China. If you’re unsure about how to deal with weeds, we can recommend herbicides for you and send free samples for you to try. We look forward to hearing from you!
Post time: May-15-2024
