Three things are certain in life: death, taxes, and weeds.
Be they dandelions or crabgrass, weeds can sprout up in lawns, gardens, or tiny cracks in the sidewalk or your driveway.
Despite some having medicinal or dietary value, all weeds choke out other plants and often turn a beautiful space into an eyesore.
Thankfully, a wide range of herbicides, better known as weedkillers, can help with any weed problems.
But with so many different products on the market, is there much difference in how fast they act?
How Long Does It Take for Weedkiller to Work?
Generally, most weed killers take 2 to 4 weeks to do their job.
Some formulas work behind the scenes, while others have visible effects.
Different Types of Weedkillers
Pesticides come in a range of formulas with different active ingredients. Knowing the herbicide classification in your weedkiller can help you understand how and how quickly it works.
Five different weedkiller types can be classified as pre-emergent or post-emergent.
It is essential to know this because post-emergent formulas only work on existing weeds. Pre-emergent recipes only work on germinating seeds.
Each kind of weedkiller has a specific purpose, so the exact timeline for their effectiveness can vary.
Yet, all post-emergent weedkillers have roughly the same kill time.
Pre-Emergent Pesticides
Pre-emergent weedkillers work over a more extended period and are only residual formulas.
The advantage of this type of weedkiller is that it can prevent new weeds from sprouting for an extended time.
Unfortunately, they aren’t designed to end existing weeds.
Generally, it’s best to use pre-emergent weed killers in the early spring.
As a seed germinates, the fragile plant embryo becomes exposed to the herbicide, killing it before sprouting.
You’ll likely need to add a few more applications during the growing season. The frequency varies by brand.
Many pre-emergent formulas last 4 to 6 months.
Post-Emergent Pesticides
Post-emergent pesticides work on existing weeds and will clear your lawn or garden in about 2 to 4 weeks.
The advantage of post-emergent formulas is the swift removal of unwanted or unsightly plants.
The drawback is that they won’t destroy seeds already present in the soil.
When choosing a post-emergent formula, examine how it works and what weeds it will affect. This can vary from one product to another.
Most of these herbicides leave little to no residue. Thus, you to use the soil once you’ve uprooted the dead weeds.
The best time for using a post-emergent weedkiller is later in spring or summer before the weeds have a chance to go to seed.
Contact Weedkillers
As the name implies, contact weedkillers begin working on contact.
Spray the growing weeds with herbicide early in the morning so the leaves have time to soak up all the poison.
Weeds will begin curling and browning within a week, and they should be dead in about two weeks.
Contact weedkillers work best on annual weeds.
Non-Selective Weedkillers
Glyphosate is the safest and most widely used active chemical in non-selective weedkillers.
It is the main ingredient in most Roundup products and is highly effective. But it can sometimes take a little longer to work.
Roundup will begin to show signs of working in as little as 6 hours and kill the plant in about 14 days.
Many other non-selective formulas won’t show effectiveness until 7 to 14 days after application. They will kill the plant in about 30 days.
These are called non-selective because they will kill any plant they come in contact with.
As a result, non-selective weedkillers are best for patios, sidewalks, or driveways.
Avoid spraying them when there is any wind or risk of rain before the herbicide can become rainproof (usually within 30 minutes to 4 hours).
Residual Weedkillers
These weedkillers remain active in the soil for an extended period and are almost always a pre-emergent formula.
As with non-selective formulas, residual herbicides can kill flowers and other desirable plants. Use them only in places where you don’t plan to grow anything, such as a driveway or patio.
Selective Weedkillers
Unlike non-selective herbicides, selective weedkillers attack certain plants while remaining harmless to others.
These poisons generally work on contact and are the perfect choice when you need something for the lawn or garden.
The effects are usually visible within a few days, and the weeds will be dead in around 14 days.
Weed and feed formulas are excellent examples of selective weedkillers.
Systemic Weedkillers
Chances are, your post-emergent weedkiller is systemic. Any part of the target plant can absorb it.
These herbicides slowly make their way down the plant, killing the root systems.
This ability makes them a great solution to many perennial weeds. The poison will travel through both creepers and root systems until every part of the plant is dead.
An excellent example of a systemic, selective weed killer is 2,4-D.