Common ragweed may be an important weed for you to identify, even if you don't care about keeping your yard weed-free for aesthetic reasons. If you're an allergy sufferer, you should be aware that common ragweed is a major source of hay fever.
Several of these weeds can cause rashes. Use proper clothing and gloves when working around these weeds, or enlist professional help to eradicate them.
Giant Ragweed (Ambrosia trifida)
Wild madder is, like sweet woodruff, in the Galium genus. Wild madder is also called "bedstraw." Apparently, people did actually once use this weed as a bedding material. Sweet woodruff is a creeping, mat-forming perennial that pretty clusters of white star-shaped flowers in spring and has very fragrant, lance-shaped dark-green leaves.
There are three plants named, “bittersweet.” American bittersweet is harmless, but Oriental bittersweet should be regarded as a weed since it can harm your trees. The third type of weed that goes by this name (bittersweet nightshade) is one of our most poisonous plants, despite being related to the tomato.
While many consider clover a “weed,” there’s really nothing wrong with having a little clover mixed into your lawn. The Irish consider various tripartite clover leaves (such as the one in the photo here) to be “shamrocks.” The tradition behind the shamrock is quite distinct from that behind four-leaf clovers.
A replicated, controlled study in grassland in 1996-1997 in Berkshire, UK (Edwards et al. 2000) found that percentage ground cover of the weed creeping thistle Cirsium arvense was reduced by 70-90% by sowing wildflower seeds on ungrazed, ploughed grassland. Sowing wildflower seeds had no effect on creeping thistle cover on undisturbed grassland, or on ploughed grassland that was grazed by rabbits Oryctolagus cuniculus.The results were part of a larger experiment that used five replicated blocks of forty-eight 2 x 2 m plots. Factors in the experiment were grazing (rabbits excluded or not), insecticide (applied or not), slug and snail control (applied or not), wild flower seeds (sown or not) and three disturbance treatments: control, ploughing and rotavating to 25 cm depth and ploughing and rotavating followed by fumigation with methyl bromide for seven days. Wildflower plots were sown with 60 species of wild flower at 1000 seeds/species/m². Rabbits were excluded with 1 m high, 3 cm mesh fencing. Quoted numbers were extracted from figures in the paper.
Here we present evidence from nine of 13 studies testing this intervention.
A randomised, replicated trial in fallow farmland in Virginia, USA (Ang et al. 1994) found that sowing plots with tall fescue Festuca arundinacea and crownvetch Coronilla varia at recommended rates reduced shoot weight of the weed creeping thistle Cirsium arvense by 96%, compared to plots with no competitor plants. Sowing competitor plants at half or double the recommended rate reduced thistle shoot weight by 84-85% and 85-86% respectively. Length and weight of thistle roots followed similar patterns. Average thistle shoot weight increased from the first to the second year of competition (6.7 vs. 44.3 g/plot), but decreased after three years of competition (11.5 g/plot). Plots were 2 x 2 m separated by 1 m, in four replicate blocks. Each block had 12 randomised treatments: 0, 0.5, 1 and 2 times the recommended sowing rate (50 and 20 kg/ha of tall fescue and crownvetch respectively) for one, two or three years. The study was part of a biological control experiment using the thistle-eating green tortoise beetle Cassida rubiginosa, which was maintained at a density of >50 adults/m². Numbers quoted were extracted from figures and converted from logarithms.
A replicated study in 1996 in a greenhouse in Queensland, Australia (Navie et al. 1998) found that under competition from buffelgrass Cenchrus ciliaris, the weed ragweed parthenium Parthenium hysterphorus had reduced average height (29.9 cm vs. 39.8 cm in control plots), weight (1.63 vs. 7.72 g/plant) and reproduction (373 vs. 1880 mature seed heads/plant and 1140 vs. 4970 viable seeds/plant). The experiment also found that the ragweed borer moth Epiblema strenuana reduced ragweed parthenium size and reproduction, and that the moth and buffelgrass competition together had a greater effect on seed head production than each did individually. Ragweed parthenium was planted in 15 pots with buffelgrass and 15 without. Two weeks after sowing, plants were thinned to one ragweed parthenium and three buffelgrass seedlings/pot. Within each set of 15 plants, five received 10 ragweed borer eggs 35 days after germination and five received 10 eggs 53 days after germination. The experiment ran for 120 days.
A randomised, replicated, controlled trial in 2005 in a greenhouse in Colorado, USA (Norton et al. 2008) found reduced growth of diffuse knapweed Centaurea diffusa (an invasive weed) when grown in competition with prairie sagewort Artemisia frigida (diffuse knapweed weight of 1.5 g/plant) or blue grama grass Bouteloua gracilis (0.5 g/plant), compared to growing diffuse knapweed alone (2.2 g/plant). Diffuse knapweed also reduced yield of prairie sagewort by 58% and of blue grama by 35% compared to growing either species alone. The experiment used 2 litre pots with one diffuse knapweed plant and two prairie sagewort or blue grama plants, and controls with each species individually. Pots containing diffuse knapweed also received one of four different treatments with herbivorous insects used for biological control. Each treatment was replicated 12 times.
Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.
This intervention involves planting species that out-compete damaging weeds, suppressing them by reducing their ground cover, growth or reproduction rate, or by increasing their mortality. The intervention is generally applied to pastureland or uncropped areas such as field margins and buffer strips. Plants grown to suppress weeds on large parts of arable land are not included here but are relevant to cover cropping actions, e.g. ‘Grow cover crops when the field is empty’, ‘Grow cover crops beneath the main crop (living mulches) or between crop rows’, ‘Grow crops in strips within a cover crop’ and ‘Incorporate leys into crop rotation’ (actions for inclusion in a future synopsis).
In addition to their growing type, common weed plants may belong to one of two families: broadleaf (Dicot) or narrow leaf (Monocot). Broadleaf types have larger leaves and grow from tap roots or fibrous root systems, whereas narrow leaf or grasses have long narrow leaves and fibrous roots systems.
So what are weeds and where do weeds grow? By definition, a weed is known as “a plant in the wrong place.” For the most part, these plants are known more for their undesirable qualities rather than for their good ones, should there be any.
Therefore, many questions concerning “where do weeds grow” can be answered by having an understanding of how they grow by type.
Types of Weeds
There are generally three types of common weed plants in regards to their growing characteristics. These include:
Of course, which weed goes and which weed stays depends on the individual gardener, though a little bit of weed info and control methods makes this decision easier.
What are Weeds?
Weeds are competitive, fighting your garden plants or lawn grass for water, light, nutrients, and space. Most are quick growers and will take over many of the areas in which you find them. While most types of weeds thrive in favorable conditions, native types may be found growing nearly anywhere the ground has been disturbed. In fact, they may even offer clues to your current soil conditions.
Weeds are an all too common occurrence in lawns and gardens. While some may be deemed useful or attractive, most types of weeds are considered a nuisance. Learning more about weed info and control can make it easier for gardeners to decide whether these weeds should be welcomed or if they must go. Let’s take a look at some common weed plants and when or what weed control methods may be necessary.