A seedling that grows slowly is more susceptible to attack for weeds than a seedling that grows quickly. A vulnerable plant, onions produce slender, upright stems and are slow to germinate. Unlike broad beans, which produce large seedlings, broad beans are less susceptible to environmental factors, except in critical times when water is scarce and pods are filling out. A transplant planted in sterile soil or potting compost has an advantage over weeds that germinate on the surface.
Depending on the conditions and season, weeds also differ in their competitive abilities. Fat hen (Chenopodium album), a tall, vigorous weed, often has the most noticeable impact on adjacent crops, although seedlings of fat hen emerge in late summer and mature to a small plant. Chickweed (Stellaria media), a low-growing herb that grows during the summer, can co-exist with tall crops during the summer, but overwintered plants will grow rapidly in early spring and may smother crops like onions and spring greens.
Weeds does not damage crops initially, especially in the early stages of growth when both weeds and crops can grow unimpeded. The need for nutrients and water increases as they grow.
The weeds grow on gardens, flowerbeds, grasses, vegetation, or even on the streets. The invasion of weeds changes the biological diversity and balance of ecological communities and threatens the survival of many plants, since these undesirable plants compete for space, nutrients, and sunlight with native species.
Weeds pose a problem in agriculture. Invading crops, smothering pastures, and sometimes even harming livestock, they decrease farm and forest productivity. The competitive nature of these plants reduces yield and quality of crops, because they compete for sunlight, nutrients, and water.
Additionally, each city’s municipality is concerned about weeds growing in public places. Concerned persons worry about how to remove these plants without endangering the health of their citizens. Nowadays, products like glyphosate herbicide can be harmful and toxic to health. In this situation, ozone is the best weed treatment because it does not contain chemicals.