This is a great question, but at the same time it is a loaded question. There are so many ways to answer this based on so many factors. For instance, what weed specifically are you trying to target? What are the weather conditions? Can that weed be prevented all together? Does the weed respond better to pre-emergent or post-emergent? And the list does not end there.
All of these questions can be overwhelming, hopefully this guide can make it easier.
Biggest Factors
Type of product
There are two main types of herbicide to consider using.
- Pre Emergent: This herbicide stops the weed before it even germinates. Essentially preventing the weed from ever “emerging” from the ground.
- Post Emergent: When using post-emergent to spray lawn weeds, the goal is to neutralize an existing weed; or one that has already “emerged”.
Time of year
Obviously stopping a weed before you ever see it sounds like the best option,so why wouldn’t you always use pre-emergent? Unfortunately, certain products are only effective in certain weather conditions, like peak summer months or winter.
For example, pre-emergent is only effective in cooler months, so applying it to a Texas Lawn in mid-July could be ineffective.
Time of year is also crucial when considering the weeds you want to target. Some weeds only grow during certain temperatures or seasons. For example, you may hear a weed referred to as a “winter weed”. This means it only is a problem in winter months and will naturally die off as the temperatures start rising.
A great example of this is Poa Annua, which is very prominent in the earlier months of the year but typically begins to burn off by March.
Soil Conditions
This is similar to time of the year but soil conditions are even more important. One huge soil condition is the soil temperature. Just because it is 70 degrees outside, does not mean the soil temperature is at 70 degrees. It takes CONSISTENT temperatures for over a week to begin to change the soil temperature.
It would also include overnight temperatures. If it is 70 degrees during the day, but drops in the 50’s during the night, the soil temperature is likely hovering around 60 degrees.
Type of weeds
Before you choose which product to use to spray lawn weeds, you will need to take the type of weed into consideration. Different types of weeds respond to different products. They also all have specific conditions that make spraying the weed more effective.
Guides for the Most Common Types of Weeds
Nutsedge
Also referred to as nutgrass, is a waxy, grassy weed that Grows during “wet season”, which in North Texas is more likely to be spring or fall. Unfortunately, there are no products that can stop the germination of nutsedge, so it is best treated by spraying post-emergent.
Crabgrass
Crabgrass also tends to grow in spring or fall. While crabgrass does respond pretty well to post emergent, it is much easier to prevent it altogether by spraying your lawn with pre-emergent.
Crabgrass begins to germinate at soil temperatures of 62 degrees or lower, so we recommend spraying this lawn weed in your spring round of pre-emergents.
Learn more about crabgrass and how to get rid of it.
Poa Annua
This nasty winter weed does not respond well to post-emergent, but luckily it can be prevented with fall pre-emergents. Poa Annua germinates once soil temperatures drop below 70 degrees.
Like mentioned above, there is little need to spray Poa Annua after March, because it will naturally burn away as temperatures increase.
Spurge
This broadleaf weed grows in hot and dry soil conditions. There is no pre-emergent for spurge so it is best treated in the peak summer months with post emergent.
Sand Burs
The weed that produces those terribly painful stickers and it is Stubborn with a capital S. It does not respond well to post emergent and after it emerges it is likely to seed and produce those painful stickers. For those reasons, it is best treated with fall pre-emergents.
Sand Burs begin germinating once soil temperatures reach below 75 degrees. Spraying fall pre-emergents combined with proper mowing practices and lots of time and patience will eliminate these terrible weeds from your lawn.
Label is Law
There is a phrase in the lawn care industry, “Label is Law.” The easiest guide to spraying lawn weeds is reading the label on the bottle of product. Many herbicides have specific restrictions not only for the efficacy of the product, but also for the safety of the individual using it.
If you are wondering if you should use a certain herbicide in July, but the label says not to use it above 60 degrees do not use it.
Not only could it result in safety concerns, but it would likely be a waste of time and money.
There are so many factors to consider when determining the best time to spray lawn weeds. While it is always nice to have a good understanding, you might want to consider allowing a professional to partner with you to make these decisions.
Gecko Green has over 30 years experience in North Texas and knows the exact timing to begin using products. That’s the expertise only a local company can provide!
