With the warm weather comes the inevitable unwanted plants or weeds. They fall from parent plants, arrive via animals, shoes, vehicles, or the wind. Some seeds can remain dormant in the soil for decades while others germinate immediately.
Annual weeds grow quickly and typically have a small root system making them easier to pull. Their life cycle starts as a seed or a piece of plant and ends once seed is produced. Annual weeds can usually be eliminated if they are removed before they go to seed. Note that a number of annual weeds overwinter as immature plants and are quick to grow in spring.
Perennial weeds are harder to eradicate. Unless removed soon after germination, they have a larger root system and often regrow from a small piece of root.
Being persistent and removing all green parts of the plants as it appears will eventually starve the root causing the plant to die. This can be accomplished through hand digging, mechanical cultivation or baking the soil for a growing season with a black plastic.
Chemical methods are available. Each chemical works slightly different and achieves different results. All herbicides, including organic ones, go through standard testing before they are registered under the Pest Controls Product Act and sold. Each herbicide comes with instructions and restrictions.
Knowing how the chemicals work helps the applicator apply the least amount of product to achieve the best results.
Mecoprop-p, 2,4-D and Dicamba work by accelerating the rate of a naturally occurring chemical in the plant resulting in rapid growth that quickly kills the plant. This is seen in the twisted elongated shape of a sprayed dandelion. To work the plant must be actively growing.
Glyphosates which are associated with the name Roundup, are nonselective which means there is a possibility of it killing any plant it touches. The herbicide works by destroying a plant enzyme that is needed in the production of food. Once the enzyme is destroyed the plant starves. Once again, the plant must be actively transporting nutrients throughout its system for the chemical to be effective.
Acetic Acid or horticultural vinegar is being sold under a few names including Round up Advanced. It can be purchased in concentrates from 5 to 30 per cent with the higher concentrations being the most effective. This chemical works by burning the top foliage off the plants which is effective in young annuals. Weeds with an established root system tend to regrow from the roots and need more than one application. Like all pesticides, follow the manufacturer’s instructions and use proper precautions as high concentrations of acetic acid can damage anything it touches.
Products that contain Iron chelate are used on lawns to kill broadleaf weeds. It has been found to be effective on a number of broadleaf weeds including dandelions and clover but repeat treatments are often needed. Like acetic acid, it kills the portion of the plant that it touches but not the roots.
There are many different ways of dealing with weeds. Which method to use is up to each individual.
Linda Tomlinson is a horticulturalist who has gardened in central Alberta for over 30 years. She can be reached at email@example.com.