Weeds Flashcards
Identification
All weeds are members of the Plantae Kingdom and are divided into two main groups
Dicots
Monocots
Dicots, commonly referred to as broadleaves, are plants whose seedlings produce two cotyledons.
Leaves of dicots usually have netlike veins and flower part usually in fours, five, of multiples thereof.
They tend to contain a main taproot and a coleoptile instead of cotyledons.
Monocots produce only a single grasslike leaf in the seedling.
However, to manage weeds effectively, they must usually be identified early, so features of seedlings are particularly important especially seed leaf shape and texture.
Leaves typically have parallel veins that run the length of their axis and flower parts in threes or multiples of three..
They can be found in two major families: grasses (Poaceae) and sedges (Cyperaceae).
Sedges can be distinguished grasses in that they contain a triangular cross section and their leaves are arranged in thees at the base instead of twos as in the case of grasses.
Important identifying features are the auricles/ligules around the collar region and flower structures such as awns/glumes on mature plants.
Mosses/Liverworts (Bryophytes) and Algae are two other groups of plants that can be classified as weeds in specific circumstances.
Mosses lack a vasculard system and are occasional pests in aquatic settings and greenhouses.
Algae are nonflowering primitive aquatic plants that often clog streams, irrigation systems, drainage ditches, etc.
Both lack stems, leaves and flower and reproduce through cell division/production of spores.
Life-Cycle and Regrowth
Most weeds begin as a seed mainly composed of three parts: an embryo, food source, and a seed coat.
Many weeds can remain dormant in the seed stage for long durations of time.
Afterwards plants enter a reproductive period in which most energy is diverted for flowering, fruit, and seed production.
Weed can be grouped as either annual, biennial, or perennial depending on their longevity.
Annuals: complete a life-cyle in a years time and can be divided into summer (germinating in spring; pigweed, puncturevine, barnyardgrass, and yellow foxtail) & winter (germinate late summer; mustards, wild oats, annual bluegrass, and filaree).
Biennials (fennel, wild carrot, hemlock, mullein, & thistles) and Perennials (Nutsedge, bermuda-grass, bindweed): Complete a lifecyle in two years or more, respectively and tend to have large underground storage organs such as tuber, bulbs, rhizomes, or creeping roots.
Successful Charactueristics
Features including abundant seed production, rapid population establishments, seed dormancy, long-term survival of buried seed, adaptations for seed dispersal, the presence of vegetative reproductive structures, and the ability to invade sites disturbed by people have ensured their survival dominnance.
Rapid root and shoot development gives the weed a distinct advantage by shading out desirable plants. Ability to survive under less than desirable conditions allows for their survival.
Most weeds seeds exhibit some degree of dormancy.
It is a good idea to assess the seed bank by taking soil samples to determine the type of weeds seeds and their abundance in a field.
The total number of weed seeds surviving in the soil or on the soil surface of an area is called the weed seed bank.
Dispersal and Movement
Barbs, hooks, spines, awns, sticky secretions, or cottony lint can attach to birds, mammals, people, or equipment.
Weed seeds may be blown around in wind, washed away in water, or transported by human/mechanical/animals.
