There is a common misconception that certain plants are always weeds. By definition, that is not the case, because weeds are nothing more than undesirable plants. If you desire it, it is not a weed. A weed is nothing more than a plant growing where it is not wanted. A dandelion, for example, might be a weed if it is found in your lawn, whereas if you are planting a garden of dandelions, and grass starts growing there, the grass is the weed. There is a common misconception that certain plants are defined as weeds. By definition, however, that is not the case, because weeds are nothing more than undesirable plants. If you desire it, it is not a weed. Weeds ruin the aesthetic value of your garden, because they do not look nice in your garden, lawn, etc. However, the real problem with weeds is that they will compete with your flowers, grass, or plants for water and nutrients, further detracting from the beauty of whatever you are growing. In this article, I will primarily be talking about lawn weeds, how to identify, how to prevent them, and how to get rid of them.
Lawn weeds can be placed into two categories. The difference between these two categories is the way they physically grow form seeds. The categories are monocots and dicots. As the names might suggest, monocots emerge from the seed sprouting one leaf, whereas dicots emerge from the seed sprouting two leaves. Monocot weeds are usually referred to as weedy grasses; and dicots are usually referred to as broadleaf weeds. Monocots include crabgrass and quackgrass, to name a couple. Dicots include dandelions and clover, to name a couple.
There are three more main categories to split weeds up even further, one of which is split up into another two categories. Perennial weeds live for longer than two years and may produce new seeds every year. Biennial weeds have a two-year life-span and usually do not produce seeds until the second year. Biennial weeds and perennial weeds are often grouped together since they require the same action to get rid of them. Annual weeds germinate from seeds, grow fully and produce more seeds in less than one year. Summer annual weeds germinate in the spring and grow in the fall. Winter annual weeds germinate in the fall or winter and grow in the spring.
In many instances there is an easy solution to get rid of unwanted weeds. One way to prevent weeds from even becoming a problem is to maintain a dense turf cover. For example, if the weeds are growing due to a problem with how compacted the soil is, killing the weeds without fixing up the topsoil is a waste of time, since new weeds will replace the dead weeds in just a matter of time. Many times the problem can be fixed simply by changing how you care for your lawn. For example, it may be as simple as watering your lawn more often or less often than you currently do. The problem may be fixed by simply mowing a little higher or a little lower, or perhaps mowing a greater number of times or a fewer number of times. The problem may be fixed by fertilizing more or fertilizing less. Each case is different depending upon your practices and depending on the weeds and the climate.
There are a number of products you can buy to kill weeds. They can basically be broken into two main categories: pre-emergence herbicides and post-emergence herbicides. As their names suggest, pre-emergence herbicides are used to control weeds before the weeds emerge, and post-emergence herbicides are used to kill the weeds after they had already emerged. Therefore, pre-emergence herbicides are most effective against annual weeds. To be effective, pre-emergence herbicides must be applied a couple weeks before the weeds germinate. If they are applied too far in advance, or after the weeds had already germinated, they will usually be powerless to control the weeds. That is where post-emergence herbicides come into play.
Post-emergence herbicides can be split up into two categories: selective post-emergence herbicides, and non-selective post-emergence herbicides. Selective post-emergence herbicides are most commonly used on lawns, since they kill many broadleaf weeds without adversely effecting grass. However, this being the nature of post-emergence herbicides, they will often kill trees, bushes, or flowers. It is extremely important to be very careful when using post-emergence herbicides in the near vicinity of flowers, shrubs, trees, bushes, etc. Non-selective post-emergence herbicides kill everything they touch indiscriminately. Therefore, non-selective post-emergence herbicides should only be used to spot treat weeds, such as perennial grassy weeds that are unaffected by selective post-emergence herbicides.